LazyFrame

Namespace: Polars.FSharp

A LazyFrame represents a logical plan of operations that will be optimized and executed only when collected.

Operations on LazyFrame are not executed immediately. Instead, they build a query plan. Use Collect() to execute the plan and get a DataFrame.

Properties & Indexers

Property	Type	Description
ColumnNames	string list	-
Columns	string list	-
DataTypes	DataType list	-
Schema	PolarsSchema	Get the schema of the LazyFrame without executing it. Uses Zero-Copy native introspection.

Constructors & Static Methods

Concat

Concatenate multiple LazyFrames.

static member Concat(
    lfs: seq<LazyFrame>,
    ?how: ConcatType,
    ?rechunk: bool,
    ?useParallel: bool
) : LazyFrame

Parameters

Name	Type	Description
lfs	seq<LazyFrame>	-
how	ConcatType (optional)	-
rechunk	bool (optional)	-
useParallel	bool (optional)	-

---

ConcatDiagonal

Concatenate multiple LazyFrames diagonally.

static member ConcatDiagonal(lfs: seq<LazyFrame>) : LazyFrame

Parameters

Name	Type	Description
lfs	seq<LazyFrame>	-

---

ConcatHorizontal

Concatenate multiple LazyFrames horizontally.

static member ConcatHorizontal(lfs: seq<LazyFrame>) : LazyFrame

Parameters

Name	Type	Description
lfs	seq<LazyFrame>	-

---

ConcatVertical

Concatenate multiple LazyFrames vertically.

static member ConcatVertical(lfs: seq<LazyFrame>) : LazyFrame

Parameters

Name	Type	Description
lfs	seq<LazyFrame>	-

---

ScanCsv

Lazily scans a CSV file into a LazyFrame.

This allows for query optimization (predicate pushdown, projection pushdown) and streaming processing of datasets larger than memory.

Lazily scans a CSV from an in-memory byte array.

Lazily scans a CSV from a Stream.

This reads the stream fully into memory to construct the Lazy execution plan.

Helper: Scan CSV with default settings

static member ScanCsv(
    path: string,
    ?schema: PolarsSchema,
    ?dtypeOverride: PolarsSchema,
    ?hasHeader: bool,
    ?separator: char,
    ?quoteChar: char,
    ?eolChar: char,
    ?ignoreErrors: bool,
    ?tryParseDates: bool,
    ?lowMemory: bool,
    ?cache: bool,
    ?glob: bool,
    ?rechunk: bool,
    ?raiseIfEmpty: bool,
    ?skipRows: uint64,
    ?skipRowsAfterHeader: uint64,
    ?skipLines: uint64,
    ?nRows: uint64,
    ?inferSchemaLength: uint64,
    ?inferSchemaFiles: uint64,
    ?nThreads: uint64,
    ?chunkSize: uint64,
    ?rowIndexName: string,
    ?rowIndexOffset: uint64,
    ?includeFilePaths: string,
    ?encoding: CsvEncoding,
    ?nullValues: seq<string>,
    ?missingIsNull: bool,
    ?commentPrefix: string,
    ?decimalComma: bool,
    ?truncateRaggedLines: bool,
    ?cloudOptions: CloudOptions
) : LazyFrame

static member ScanCsv(
    buffer: byte[],
    ?schema: PolarsSchema,
    ?dtypeOverride: PolarsSchema,
    ?hasHeader: bool,
    ?separator: char,
    ?quoteChar: char,
    ?eolChar: char,
    ?ignoreErrors: bool,
    ?tryParseDates: bool,
    ?lowMemory: bool,
    ?cache: bool,
    ?glob: bool,
    ?rechunk: bool,
    ?raiseIfEmpty: bool,
    ?skipRows: uint64,
    ?skipRowsAfterHeader: uint64,
    ?skipLines: uint64,
    ?nRows: uint64,
    ?inferSchemaLength: uint64,
    ?inferSchemaFiles: uint64,
    ?nThreads: uint64,
    ?chunkSize: uint64,
    ?rowIndexName: string,
    ?rowIndexOffset: uint64,
    ?includeFilePaths: string,
    ?encoding: CsvEncoding,
    ?nullValues: seq<string>,
    ?missingIsNull: bool,
    ?commentPrefix: string,
    ?decimalComma: bool,
    ?truncateRaggedLines: bool
) : LazyFrame

static member ScanCsv(
    stream: Stream,
    ?schema: PolarsSchema,
    ?hasHeader: bool,
    ?separator: char,
    ?quoteChar: char,
    ?eolChar: char,
    ?ignoreErrors: bool,
    ?tryParseDates: bool,
    ?lowMemory: bool,
    ?cache: bool,
    ?glob: bool,
    ?rechunk: bool,
    ?raiseIfEmpty: bool,
    ?skipRows: uint64,
    ?skipRowsAfterHeader: uint64,
    ?skipLines: uint64,
    ?nRows: uint64,
    ?inferSchemaLength: uint64,
    ?inferSchemaFiles: uint64,
    ?nThreads: uint64,
    ?chunkSize: uint64,
    ?rowIndexName: string,
    ?rowIndexOffset: uint64,
    ?includeFilePaths: string,
    ?encoding: CsvEncoding,
    ?nullValues: seq<string>,
    ?missingIsNull: bool,
    ?commentPrefix: string,
    ?decimalComma: bool,
    ?truncateRaggedLines: bool
) : LazyFrame

static member ScanCsv(path: string) : LazyFrame

Parameters

Name	Type	Description
path	string	-
schema	PolarsSchema (optional)	-
dtypeOverride	PolarsSchema (optional)	-
hasHeader	bool (optional)	-
separator	char (optional)	-
quoteChar	char (optional)	-
eolChar	char (optional)	-
ignoreErrors	bool (optional)	-
tryParseDates	bool (optional)	-
lowMemory	bool (optional)	-
cache	bool (optional)	-
glob	bool (optional)	-
rechunk	bool (optional)	-
raiseIfEmpty	bool (optional)	-
skipRows	uint64 (optional)	-
skipRowsAfterHeader	uint64 (optional)	-
skipLines	uint64 (optional)	-
nRows	uint64 (optional)	-
inferSchemaLength	uint64 (optional)	-
inferSchemaFiles	uint64 (optional)	-
nThreads	uint64 (optional)	-
chunkSize	uint64 (optional)	-
rowIndexName	string (optional)	-
rowIndexOffset	uint64 (optional)	-
includeFilePaths	string (optional)	-
encoding	CsvEncoding (optional)	-
nullValues	seq<string> (optional)	-
missingIsNull	bool (optional)	-
commentPrefix	string (optional)	-
decimalComma	bool (optional)	-
truncateRaggedLines	bool (optional)	-
cloudOptions	CloudOptions (optional)	-
buffer	byte[]	-
stream	Stream	-

---

ScanDb

Scan a database query lazily. Requires a factory function to create new IDataReaders for potential multi-pass scans.

[Lazy][Streaming] Scan a database DataReader directly.

static member ScanDb(readerFactory: (unit -> IDataReader), ?batchSize: int, ?useBuffered: bool) : LazyFrame
static member ScanDb(reader: IDataReader, ?batchSize: int) : LazyFrame

Parameters

Name	Type	Description
readerFactory	(unit -> IDataReader)	-
batchSize	int (optional)	-
useBuffered	bool (optional)	-
reader	IDataReader	-

---

ScanDelta

Create a LazyFrame by scanning a Delta Lake table.

static member ScanDelta(
    path: string,
    ?version: uint64,
    ?datetime: string,
    ?nRows: uint64,
    ?parallelStrategy: ParallelStrategy,
    ?lowMemory: bool,
    ?useStatistics: bool,
    ?glob: bool,
    ?rechunk: bool,
    ?cache: bool,
    ?rowIndexName: string,
    ?rowIndexOffset: uint32,
    ?includePathColumn: string,
    ?schema: PolarsSchema,
    ?hivePartitioning: bool,
    ?hivePartitionSchema: PolarsSchema,
    ?tryParseHiveDates: bool,
    ?cloudOptions: CloudOptions
) : LazyFrame

Parameters

Name	Type	Description
path	string	Path to the Delta Lake table (folder containing _delta_log).
version	uint64 (optional)	The version of the table to read (e.g., 0L, 1L). Mutually exclusive with datetime.
datetime	string (optional)	The timestamp to read (ISO-8601 string, e.g., "2026-02-09T12:00:00Z"). Mutually exclusive with version.
nRows	uint64 (optional)	-
parallelStrategy	ParallelStrategy (optional)	-
lowMemory	bool (optional)	-
useStatistics	bool (optional)	-
glob	bool (optional)	-
rechunk	bool (optional)	-
cache	bool (optional)	-
rowIndexName	string (optional)	-
rowIndexOffset	uint32 (optional)	-
includePathColumn	string (optional)	-
schema	PolarsSchema (optional)	-
hivePartitioning	bool (optional)	-
hivePartitionSchema	PolarsSchema (optional)	-
tryParseHiveDates	bool (optional)	-
cloudOptions	CloudOptions (optional)	-

Returns: A new LazyFrame.

---

ScanIpc

Lazily read an Arrow IPC (Feather v2) file, multiple files via glob patterns, or cloud storage.

Lazily read Arrow IPC (Feather v2) from in-memory bytes.

Lazily read Arrow IPC (Feather v2) from a Stream.

static member ScanIpc(
    path: string,
    ?schema: PolarsSchema,
    ?nRows: uint64,
    ?rechunk: bool,
    ?cache: bool,
    ?glob: bool,
    ?rowIndexName: string,
    ?rowIndexOffset: uint32,
    ?includePathColumn: string,
    ?hivePartitioning: bool,
    ?hivePartitionSchema: PolarsSchema,
    ?tryParseHiveDates: bool,
    ?cloudOptions: CloudOptions
) : LazyFrame

static member ScanIpc(
    buffer: byte[],
    ?schema: PolarsSchema,
    ?nRows: uint64,
    ?rechunk: bool,
    ?cache: bool,
    ?rowIndexName: string,
    ?rowIndexOffset: uint32,
    ?includePathColumn: string,
    ?hivePartitioning: bool,
    ?hivePartitionSchema: PolarsSchema,
    ?tryParseHiveDates: bool
) : LazyFrame

static member ScanIpc(
    stream: Stream,
    ?schema: PolarsSchema,
    ?nRows: uint64,
    ?rechunk: bool,
    ?cache: bool,
    ?rowIndexName: string,
    ?rowIndexOffset: uint32,
    ?includePathColumn: string,
    ?hivePartitioning: bool,
    ?hivePartitionSchema: PolarsSchema,
    ?tryParseHiveDates: bool
) : LazyFrame

Parameters

Name	Type	Description
path	string	-
schema	PolarsSchema (optional)	-
nRows	uint64 (optional)	-
rechunk	bool (optional)	-
cache	bool (optional)	-
glob	bool (optional)	-
rowIndexName	string (optional)	-
rowIndexOffset	uint32 (optional)	-
includePathColumn	string (optional)	-
hivePartitioning	bool (optional)	-
hivePartitionSchema	PolarsSchema (optional)	-
tryParseHiveDates	bool (optional)	-
cloudOptions	CloudOptions (optional)	-
buffer	byte[]	-
stream	Stream	-

NOTE

This reads the stream fully into memory to construct the Lazy execution plan.

---

ScanNdjson

Lazily read a NDJSON file.

Lazily read NDJSON from in-memory bytes.

Lazily read NDJSON from a Stream.

static member ScanNdjson(
    path: string,
    ?schema: PolarsSchema,
    ?inferSchemaLen: uint64,
    ?batchSize: uint64,
    ?nRows: uint64,
    ?lowMemory: bool,
    ?rechunk: bool,
    ?ignoreErrors: bool,
    ?rowIndexName: string,
    ?rowIndexOffset: uint32,
    ?includePathColumn: string,
    ?cloudOptions: CloudOptions
) : LazyFrame

static member ScanNdjson(
    buffer: byte[],
    ?schema: PolarsSchema,
    ?inferSchemaLen: uint64,
    ?batchSize: uint64,
    ?nRows: uint64,
    ?lowMemory: bool,
    ?rechunk: bool,
    ?ignoreErrors: bool,
    ?rowIndexName: string,
    ?rowIndexOffset: uint32
) : LazyFrame

static member ScanNdjson(
    stream: Stream,
    ?schema: PolarsSchema,
    ?inferSchemaLen: uint64,
    ?batchSize: uint64,
    ?nRows: uint64,
    ?lowMemory: bool,
    ?rechunk: bool,
    ?ignoreErrors: bool,
    ?rowIndexName: string,
    ?rowIndexOffset: uint32
) : LazyFrame

Parameters

Name	Type	Description
path	string	-
schema	PolarsSchema (optional)	-
inferSchemaLen	uint64 (optional)	-
batchSize	uint64 (optional)	-
nRows	uint64 (optional)	-
lowMemory	bool (optional)	-
rechunk	bool (optional)	-
ignoreErrors	bool (optional)	-
rowIndexName	string (optional)	-
rowIndexOffset	uint32 (optional)	-
includePathColumn	string (optional)	-
cloudOptions	CloudOptions (optional)	-
buffer	byte[]	-
stream	Stream	-

---

ScanParquet

Scan a parquet file into a LazyFrame.

Lazily read from a parquet file or a common cloud store (S3, GCS, Azure, etc.).

[Memory] Lazily read parquet from a byte array (in-memory buffer).

static member ScanParquet(
    path: string,
    ?nRows: uint64,
    ?parallelStrategy: ParallelStrategy,
    ?lowMemory: bool,
    ?useStatistics: bool,
    ?glob: bool,
    ?allowMissingColumns: bool,
    ?rechunk: bool,
    ?cache: bool,
    ?rowIndexName: string,
    ?rowIndexOffset: uint32,
    ?includePathColumn: string,
    ?schema: PolarsSchema,
    ?hivePartitioning: bool,
    ?hivePartitionSchema: PolarsSchema,
    ?tryParseHiveDates: bool,
    ?cloudOptions: CloudOptions
) : LazyFrame

static member ScanParquet(
    buffer: byte[],
    ?nRows: uint64,
    ?parallelStrategy: ParallelStrategy,
    ?lowMemory: bool,
    ?useStatistics: bool,
    ?glob: bool,
    ?allowMissingColumns: bool,
    ?rechunk: bool,
    ?cache: bool,
    ?rowIndexName: string,
    ?rowIndexOffset: uint32,
    ?includePathColumn: string,
    ?schema: PolarsSchema,
    ?hivePartitioning: bool,
    ?hivePartitionSchema: PolarsSchema,
    ?tryParseHiveDates: bool
) : LazyFrame

Parameters

Name	Type	Description
path	string	Path to file or cloud location.
nRows	uint64 (optional)	Stop reading after n rows.
parallelStrategy	ParallelStrategy (optional)	-
lowMemory	bool (optional)	Reduce memory pressure at the expense of performance.
useStatistics	bool (optional)	Use parquet statistics to prune row groups.
glob	bool (optional)	Expand path using globbing rules.
allowMissingColumns	bool (optional)	If true, do not fail if columns are missing.
rechunk	bool (optional)	Rechunk the memory to contiguous chunks when reading. (default: false)
cache	bool (optional)	Cache the result after reading. (default: true)
rowIndexName	string (optional)	If provided, add a row index column with this name.
rowIndexOffset	uint32 (optional)	Start index for the row index column.
includePathColumn	string (optional)	If provided, add a column with the path of the file.
schema	PolarsSchema (optional)	Overwrite the schema of the dataset.
hivePartitioning	bool (optional)	-
hivePartitionSchema	PolarsSchema (optional)	The schema of the hive partitions.
tryParseHiveDates	bool (optional)	Attempt to parse hive values as Date/Datetime.
cloudOptions	CloudOptions (optional)	Options for cloud storage (AWS S3, Azure Blob, GCS, etc.).
buffer	byte[]	The byte array containing parquet data.

---

ScanSeq

Lazily scan a sequence of objects using Apache Arrow Stream Interface. This supports predicate pushdown and streaming execution. Data is pulled from the sequence only when needed.

static member ScanSeq(data: seq<'T>, ?batchSize: int, ?useBuffered: bool) : LazyFrame

Parameters

Name	Type	Description
data	seq<'T>	The data source sequence.
batchSize	int (optional)	Rows per Arrow batch (default: 100,000).
useBuffered	bool (optional)	Choose whether disk buffer file needed (for big data)

---

Instance Methods

AsQueryable

Convert LazyFrame into an IQueryable LINQ query provider. Operations will be translated to Polars Expressions and compiled into execution plans.

Directly creates an IQueryable with type inferred from an existing sample sequence

member AsQueryable : unit -> IQueryable<'T>
member AsQueryable(sample: seq<'T>) : IQueryable<'T>

Parameters

Name	Type	Description
sample	seq<'T>	-

---

BottomK

Get the bottom k rows based on the given columns.

member BottomK(k: int, by: seq<'a>, ?reverse: seq<bool>) : LazyFrame
member BottomK(k: int, by: seq<'a>, reverse: bool) : LazyFrame

Parameters

Name	Type	Description
k	int	-
by	seq<'a>	-
reverse	seq<bool> (optional)	-

---

Cast

Cast LazyFrame column(s) to the specified dtype(s) using a dictionary mapping.

Cast all columns in the LazyFrame to the specified dtype.

Cast columns matching an Expr/Selector to a specific DataType.

Cast multiple expressions/selectors to their target DataTypes. Example: lf.Cast([ (pl.cs.Numeric(), DataType.Float32); (col("Id"), DataType.Int32) ])

member Cast(dtypes: seq<(string * DataType)>, ?strict: bool) : LazyFrame
member Cast(dtype: DataType, ?strict: bool) : LazyFrame
member Cast(expr: Expr, dtype: DataType, ?strict: bool) : LazyFrame
member Cast(dtypes: seq<(Expr * DataType)>, ?strict: bool) : LazyFrame

Parameters

Name	Type	Description
dtypes	seq<(string * DataType)> / seq<(Expr * DataType)>	-
strict	bool (optional)	-
dtype	DataType	-
expr	Expr	-

---

Clear

Create an empty (n=0) or n-row null-filled (n>0) copy of the LazyFrame. Returns a n-row null-filled LazyFrame with an identical schema.

member Clear(?n: int64) : LazyFrame

Parameters

Name	Type	Description
n	int64 (optional)	Number of (null-filled) rows to return in the cleared frame.

Returns: A new LazyFrame.

---

Clone

member Clone : unit -> LazyFrame

---

Collect

Execute the plan and return a DataFrame.

member Collect(?engine: Engine) : DataFrame

Parameters

Name	Type	Description
engine	Engine (optional)	-

---

CollectAsync

member CollectAsync(?engine: Engine, ?cancellationToken: CancellationToken) : Task<DataFrame>

Parameters

Name	Type	Description
engine	Engine (optional)	-
cancellationToken	CancellationToken (optional)	-

---

CollectBatchesAsync

Streams materialized DataFrame batches asynchronously using the native Polars streaming batch engine. Native memory consumption is strictly bounded by O(batch) size.

member CollectBatchesAsync(
    ?chunkSize: int64,
    ?engine: Engine,
    ?maintainOrder: bool,
    ?cancellationToken: CancellationToken
) : IAsyncEnumerable<DataFrame>

Parameters

Name	Type	Description
chunkSize	int64 (optional)	Maximum row count per native batch (0 uses Polars default batch size).
engine	Engine (optional)	Execution engine selection.
maintainOrder	bool (optional)	Whether to enforce deterministic row ordering across batches.
cancellationToken	CancellationToken (optional)	Optional cooperative cancellation token.

Returns: An asynchronous stream of DataFrame batches.

---

CollectSchema

member CollectSchema : unit -> PolarsSchema

---

Count

Return the number of non-null elements for each column.

member Count : unit -> LazyFrame

---

Describe

Generate a summary statistics DataFrame (count, mean, std, min, 25%, 50%, 75%, max). Similar to pandas/polars describe(). Notice: This will collect LazyFrame once, but LazyFrame won't be consumed.

member Describe : unit -> DataFrame

---

Drop

Drop selected columns by selector.

Drop selected columns by column names.

Drop columns by specific Expressions.

member Drop(selector: Selector) : LazyFrame
member Drop([<ParamArray>] columns: string[]) : LazyFrame
member Drop(columns: 'a) : LazyFrame
member Drop(exprs: seq<Expr>) : LazyFrame
member Drop([<ParamArray>] exprs: Expr[]) : LazyFrame

Parameters

Name	Type	Description
selector	Selector	-
columns	string[] / 'a	-
exprs	seq<Expr> / Expr[]	-

---

DropNans

Drop rows containing one or more NaN values.

Drop rows with NaN in specific columns.

Drop rows with NaN by specific Expressions.

member DropNans(?subset: Selector) : LazyFrame
member DropNans([<ParamArray>] subset: string[]) : LazyFrame
member DropNans([<ParamArray>] exprs: Expr[]) : LazyFrame

Parameters

Name	Type	Description
subset	Selector (optional) / string[]	-
exprs	Expr[]	-

---

DropNulls

Drop rows containing one or more Null values.

Drop rows with Nulls in specific columns.

Drop rows with Nulls by specific Expressions.

member DropNulls(?subset: Selector) : LazyFrame
member DropNulls([<ParamArray>] subset: string[]) : LazyFrame
member DropNulls([<ParamArray>] exprs: Expr[]) : LazyFrame

Parameters

Name	Type	Description
subset	Selector (optional) / string[]	-
exprs	Expr[]	-

---

Explain

Print the query plan.

member Explain(?optimized: bool) : string

Parameters

Name	Type	Description
optimized	bool (optional)	-

---

Explode

member Explode(selector: Selector, ?emptyAsNull: bool, ?keepNulls: bool) : LazyFrame
member Explode(columns: seq<string>) : LazyFrame
member Explode(column: string) : LazyFrame

Parameters

Name	Type	Description
selector	Selector	-
emptyAsNull	bool (optional)	-
keepNulls	bool (optional)	-
columns	seq<string>	-
column	string	-

---

FillNan

Fill NaN values in floating point columns with a specified Expression.

member FillNan(fillValue: Expr) : LazyFrame

Parameters

Name	Type	Description
fillValue	Expr	-

---

FillNull

Fill null values in all columns with a specified Expression.

member FillNull(fillValue: Expr) : LazyFrame

Parameters

Name	Type	Description
fillValue	Expr	-

---

Filter

Filter rows based on a boolean expression.

In a LazyFrame, this operation is added to the logical plan and is optimized before execution. Polars will attempt to push this filter down as close to the data source as possible (Predicate Pushdown).

member Filter(expr: Expr) : LazyFrame
member Filter(series: Series) : LazyFrame
member Filter(mask: seq<bool>) : LazyFrame

Parameters

Name	Type	Description
expr	Expr	-
series	Series	-
mask	seq<bool>	-

---

First

member First : unit -> LazyFrame

---

Gather

Selects rows from this LazyFrame at the given indices.

member Gather(index: seq<int64>, ?nullOnOutOfBounds: bool) : LazyFrame

Parameters

Name	Type	Description
index	seq<int64>	The indices of the rows to select.
nullOnOutOfBounds	bool (optional)	If true when an index is out-of-bounds a null row will be generated instead of raising an error.

---

GatherEvery

Take every nth row in the Frame and return as a new Frame.

member GatherEvery(n: uint64, ?offset: uint64) : LazyFrame

Parameters

Name	Type	Description
n	uint64	Gather every n-th row.
offset	uint64 (optional)	Starting Index

---

GroupBy

Start a GroupBy operation.

member GroupBy(keys: seq<'a>, ?maintainOrder: bool) : LazyGroupBy

Parameters

Name	Type	Description
keys	seq<'a>	-
maintainOrder	bool (optional)	-

---

GroupByDynamic

Start a dynamic group-by (rolling window) operation. Returns a Builder.

member GroupByDynamic(
    indexCol: string,
    every: Dur,
    ?period: Dur,
    ?offset: Dur,
    ?by: seq<'a>,
    ?label: Label,
    ?includeBoundaries: bool,
    ?closedWindow: ClosedInterval,
    ?startBy: StartBy
) : LazyGroupBy

Parameters

Name	Type	Description
indexCol	string	-
every	Dur	-
period	Dur (optional)	-
offset	Dur (optional)	-
by	seq<'a> (optional)	-
label	Label (optional)	-
includeBoundaries	bool (optional)	-
closedWindow	ClosedInterval (optional)	-
startBy	StartBy (optional)	-

---

GroupByRolling

Start a rolling group-by operation. Returns a Builder.

member GroupByRolling(
    indexCol: string,
    period: Dur,
    ?offset: Dur,
    ?by: seq<'a>,
    ?closedWindow: ClosedInterval
) : LazyGroupBy

Parameters

Name	Type	Description
indexCol	string	-
period	Dur	-
offset	Dur (optional)	-
by	seq<'a> (optional)	-
closedWindow	ClosedInterval (optional)	-

---

Head

member Head(?n: uint32) : LazyFrame

Parameters

Name	Type	Description
n	uint32 (optional)	-

---

Interpolate

Interpolate intermediate values. The interpolation method is linear. Nulls at the beginning and end of the series remain null.

member Interpolate : unit -> LazyFrame

---

Join

Join with another LazyFrame using column names.

member Join(
    other: LazyFrame,
    leftOn: seq<Expr>,
    rightOn: seq<Expr>,
    how: JoinType,
    ?suffix: string,
    ?validation: JoinValidation,
    ?coalesce: JoinCoalesce,
    ?maintainOrder: JoinMaintainOrder,
    ?joinSide: JoinSide,
    ?nullsEqual: bool,
    ?sliceOffset: int64,
    ?sliceLen: uint64
) : LazyFrame

member Join(
    other: LazyFrame,
    on: seq<Expr>,
    how: JoinType,
    ?suffix: string,
    ?validation: JoinValidation,
    ?coalesce: JoinCoalesce,
    ?maintainOrder: JoinMaintainOrder,
    ?joinSide: JoinSide,
    ?nullsEqual: bool,
    ?sliceOffset: int64,
    ?sliceLen: uint64
) : LazyFrame

Parameters

Name	Type	Description
other	LazyFrame	The right DataFrame to join with.
leftOn	seq<Expr>	Column names in the left DataFrame to join on.
rightOn	seq<Expr>	Column names in the right DataFrame to join on.
how	JoinType	Type of join (Inner, Left, Outer, Cross, etc.). Default is Inner.
suffix	string (optional)	Suffix to append to columns with same name in right DataFrame. Default "_right".
validation	JoinValidation (optional)	Check if join keys are unique.
coalesce	JoinCoalesce (optional)	How to coalesce the join keys.
maintainOrder	JoinMaintainOrder (optional)	How to maintain the order of the join.
joinSide	JoinSide (optional)	Specifies the strategy for the hash join build side.
nullsEqual	bool (optional)	Consider nulls as equal.
sliceOffset	int64 (optional)	Slice the result starting at this offset.
sliceLen	uint64 (optional)	Length of the slice.
on	seq<Expr>	-

---

JoinAsOf

Perform an As-of join (also known as a time-series join).

This is similar to a left join except that we match on nearest key rather than equal keys. The join keys must be sorted.

member JoinAsOf(
    other: LazyFrame,
    leftOn: Expr,
    rightOn: Expr,
    tolerance: Tolerance,
    ?strategy: AsofStrategy,
    ?byLeft: seq<Expr>,
    ?byRight: seq<Expr>,
    ?allowEq: bool,
    ?checkSorted: bool,
    ?suffix: string,
    ?validation: JoinValidation,
    ?coalesce: JoinCoalesce,
    ?maintainOrder: JoinMaintainOrder,
    ?joinSide: JoinSide,
    ?nullsEqual: bool,
    ?sliceOffset: int64,
    ?sliceLen: uint64
) : LazyFrame

Parameters

Name	Type	Description
other	LazyFrame	The right LazyFrame to join with.
leftOn	Expr	Join key of the left LazyFrame. Must be sorted.
rightOn	Expr	Join key of the right LazyFrame. Must be sorted.
tolerance	Tolerance	Tolerance as a time duration string (e.g., "2h", "10s", "1d"), int or double or TimeSpan. Matches that are further away than this duration are discarded.
strategy	AsofStrategy (optional)	The strategy to determine which value is "nearest" (Backward, Forward, or Nearest). Defaults to AsofStrategy.Backward.
byLeft	seq<Expr> (optional)	-
byRight	seq<Expr> (optional)	-
allowEq	bool (optional)	If true, allow exact matches to be included in the result. If false, a match must be strictly unequal (e.g. less than for Backward strategy) to the key.
checkSorted	bool (optional)	Check if the join keys are sorted. If false, the user must ensure keys are sorted; otherwise results are undefined (but execution is faster).
suffix	string (optional)	Suffix to append to columns with name conflicts. Defaults to "_right".
validation	JoinValidation (optional)	Check if join keys are unique (mostly relevant for the 'by' columns).
coalesce	JoinCoalesce (optional)	How to coalesce the join keys.
maintainOrder	JoinMaintainOrder (optional)	How to maintain the order of the join.
joinSide	JoinSide (optional)	pecifies the strategy for the hash join build side.
nullsEqual	bool (optional)	Consider nulls as equal.
sliceOffset	int64 (optional)	Slice the result starting at this offset (optimization).
sliceLen	uint64 (optional)	Length of the slice to keep.

---

JoinWhere

Join with another LazyFrame using multiple boolean expressions.

member JoinWhere(
    other: LazyFrame,
    predicates: seq<Expr>,
    ?how: JoinType,
    ?suffix: string,
    ?validation: JoinValidation,
    ?coalesce: JoinCoalesce,
    ?maintainOrder: JoinMaintainOrder,
    ?nullsEqual: bool
) : LazyFrame

Parameters

Name	Type	Description
other	LazyFrame	-
predicates	seq<Expr>	-
how	JoinType (optional)	-
suffix	string (optional)	-
validation	JoinValidation (optional)	-
coalesce	JoinCoalesce (optional)	-
maintainOrder	JoinMaintainOrder (optional)	-
nullsEqual	bool (optional)	-

---

Last

Get the last row.

member Last : unit -> LazyFrame

---

Limit

Get the first n rows.

member Limit(?n: uint32) : LazyFrame

Parameters

Name	Type	Description
n	uint32 (optional)	Number of rows to return.

---

MatchToSchema

member MatchToSchema(
    schema: PolarsSchema,
    ?extraColumns: ExtraColumnsPolicy,
    ?defaultConfig: MatchSchemaConfig,
    ?columnOverrides: Map<string, MatchSchemaConfig>
) : LazyFrame

Parameters

Name	Type	Description
schema	PolarsSchema	-
extraColumns	ExtraColumnsPolicy (optional)	-
defaultConfig	MatchSchemaConfig (optional)	-
columnOverrides	Map<string, MatchSchemaConfig> (optional)	-

---

Max

Aggregate the columns in the Frame to their maximum value.

member Max : unit -> LazyFrame

---

Mean

Aggregate the columns in the Frame to their mean value.

member Mean : unit -> LazyFrame

---

Median

Aggregate the columns in the Frame to their median value.

member Median : unit -> LazyFrame

---

Melt

member Melt(
    index: Selector,
    on: Selector,
    variableName: string,
    valueName: string
) : LazyFrame

member Melt(
    index: seq<string>,
    on: seq<string>,
    ?variableName: string,
    ?valueName: string
) : LazyFrame

Parameters

Name	Type	Description
index	Selector / seq<string>	-
on	Selector / seq<string>	-
variableName	string / string (optional)	-
valueName	string / string (optional)	-

---

Merge

Initiates a Merge (upsert) plan using this LazyFrame as the target and the given source. The on selector is expanded against the target to determine the join keys.

member Merge(source: LazyFrame, on: IColumnExpr) : MergePlan

Parameters

Name	Type	Description
source	LazyFrame	The source LazyFrame containing updates/inserts.
on	IColumnExpr	A column expression (e.g., pl.col "Id") or selector (e.g., pl.cs.endsWith "Id") that resolves to the merge key columns.

Returns: A MergePlan that can be further configured and then executed.

---

MergeCatalogRecords

Starts building a Merge (Upsert) operation using this LazyFrame as the source.

member MergeCatalogRecords(
    catalog: UnityCatalog,
    catalogName: string,
    schemaName: string,
    tableName: string,
    mergeKeys: string[],
    ?canEvolve: bool,
    ?cloudOptions: CloudOptions
) : DeltaMergeBuilder

Parameters

Name	Type	Description
catalog	UnityCatalog	-
catalogName	string	-
schemaName	string	-
tableName	string	-
mergeKeys	string[]	-
canEvolve	bool (optional)	-
cloudOptions	CloudOptions (optional)	-

---

MergeDeltaOrdered

Starts a fluent builder to merge a LazyFrame into a Delta Lake table with strict, order-preserving SQL MERGE semantics.

Unlike traditional merge methods, this builder guarantees that chained actions (Update, Delete, Insert) are evaluated exactly in the order they are defined. If no actions are specified before execution, it intelligently defaults to a standard Upsert (WhenMatchedUpdate + WhenNotMatchedInsert).

member MergeDeltaOrdered(
    path: string,
    mergeKeys: seq<string>,
    ?canEvolve: bool,
    ?cloudOptions: CloudOptions
) : DeltaMergeBuilder

Parameters

Name	Type	Description
path	string	The URI to the target Delta Lake table (local or cloud).
mergeKeys	seq<string>	The column names to join on (must exist in both the Source DataFrame and Target Delta table).
canEvolve	bool (optional)	If set to true, allows schema evolution (e.g., adding new columns from the Source to the Target). Default is false.
cloudOptions	CloudOptions (optional)	Cloud storage credentials and configuration (e.g., AWS S3, Azure Blob).

Returns: A DeltaMergeBuilder instance used to chain match conditions, culminating in a call to .Execute().

---

MergeSorted

Take two sorted DataFrames and merge them by the sorted key. The output of this operation will also be sorted. It is the callers responsibility that the frames are sorted in ascending order by the key, with null keys at the end, otherwise the order of the output will not make sense. The schemas of both LazyFrames must be equal.

member MergeSorted(other: LazyFrame, key: string, ?maintainOrder: bool) : LazyFrame
member MergeSorted(other: LazyFrame, key: string[], ?maintainOrder: bool) : LazyFrame

Parameters

Name	Type	Description
other	LazyFrame	Other DataFrame that must be merged
key	string / string[]	Key that is sorted.
maintainOrder	bool (optional)	If True, the output is guaranteed to have left-biased ordering for equal keys: rows from the left frame appear before rows from the right frame when their keys are equal.

---

Min

Aggregate the columns in the Frame to their minimum value.

member Min : unit -> LazyFrame

---

NullCount

Aggregate the columns in the Frame as the sum of their null value count.

member NullCount : unit -> LazyFrame

---

Orderby

member Orderby(expr: Expr, desc: bool) : LazyFrame

Parameters

Name	Type	Description
expr	Expr	-
desc	bool	-

---

Pipe

Offers a structured way to apply a sequence of user-defined functions (UDFs).

member Pipe(func: (LazyFrame -> 'T)) : 'T

Parameters

Name	Type	Description
func	(LazyFrame -> 'T)	A function that receives the current expression and returns a value of type T. Typically this function wraps several Polars API calls that operate on the given expression.

Returns: The result of applying function to this LazyFrame.

---

PipeWithSchema

Allows to alter the lazy frame during the plan stage with the resolved schema.

In contrast to pipe, this method does not execute function immediately but only during the plan stage. This allows to use the resolved schema of the input to dynamically alter the lazy frame. This also means that any exceptions raised by function will only be emitted during the plan stage.

member PipeWithSchema(func: (LazyFrame -> (PolarsSchema -> LazyFrame))) : LazyFrame

Parameters

Name	Type	Description
func	(LazyFrame -> (PolarsSchema -> LazyFrame))	Callable; will receive the frame as the first parameter and the resolved schema as the second parameter.

---

Pivot

Pivot the LazyFrame.

Important: Lazy pivot requires an eager onColumns DataFrame to determine the output schema (column names) during the planning phase.

Pivot the LazyFrame using column names.

Pivot the LazyFrame using column names and a custom aggregation expression.

member Pivot(
    index: Selector,
    columns: Selector,
    values: Selector,
    onColumns: DataFrame,
    ?aggregateExpr: Expr,
    ?aggregateFunction: PivotAgg,
    ?maintainOrder: bool,
    ?separator: string,
    ?columnNaming: PivotColumnNaming
) : LazyFrame

member Pivot(
    index: seq<string>,
    columns: seq<string>,
    values: seq<string>,
    onColumns: DataFrame,
    ?aggregateFunction: PivotAgg,
    ?maintainOrder: bool,
    ?separator: string,
    ?columnNaming: PivotColumnNaming
) : LazyFrame

member Pivot(
    index: seq<string>,
    columns: seq<string>,
    values: seq<string>,
    onColumns: DataFrame,
    aggregateExpr: Expr,
    ?maintainOrder: bool,
    ?separator: string,
    ?columnNaming: PivotColumnNaming
) : LazyFrame

Parameters

Name	Type	Description
index	Selector / seq<string>	Selector for the index column(s) (the rows).
columns	Selector / seq<string>	Selector for the column(s) to pivot (the new column headers).
values	Selector / seq<string>	Selector for the value column(s) to populate the cells.
onColumns	DataFrame	An Eager DataFrame containing the unique values of the columns. This is strictly used for schema inference.
aggregateExpr	Expr (optional)	Optional expression to aggregate the values. If null, uses aggregateFunction.
aggregateFunction	PivotAgg (optional)	Aggregation function to use if aggregateExpr is null. Default is First.
maintainOrder	bool (optional)	Sort the result by the index column.
separator	string (optional)	Separator used to combine column names when multiple value columns are selected.
columnNaming	PivotColumnNaming (optional)	Controls how column names are constructed. Default is Auto.

Returns: A new LazyFrame with the pivot operation applied.

---

PrintSchema

member PrintSchema : unit -> unit

---

Quantile

Aggregate the columns in the Frame to their quantile value.

member Quantile(quantile: float, ?method: QuantileMethod) : LazyFrame

Parameters

Name	Type	Description
quantile	float	Quantile between 0.0 and 1.0.
method	QuantileMethod (optional)	['nearest’, ‘higher’, ‘lower’, ‘midpoint’, ‘linear’] Interpolation method.

---

Remove

Remove rows that match the predicate. This is the exact opposite of Filter. Rows where the predicate evaluates to False or Null are kept.

member Remove(predicate: Expr) : LazyFrame
member Remove(predicate: Series) : LazyFrame
member Remove(mask: seq<bool>) : LazyFrame

Parameters

Name	Type	Description
predicate	Expr / Series	-
mask	seq<bool>	-

---

Rename

Rename the lazyframe columns using a sequence of (oldName, newName) tuples. Example: lf.Rename [ "colA", "col1"; "colB", "col2" ]

Rename the lazyframe columns using a dictionary mapping old column names to new column names. Example: lf.Rename (dict [ "colA", "col1"; "colB", "col2" ])

member Rename(mapping: seq<(string * string)>, ?strict: bool) : LazyFrame
member Rename(mapping: IReadOnlyDictionary<string, string>, ?strict: bool) : LazyFrame

Parameters

Name	Type	Description
mapping	seq<(string * string)> / IReadOnlyDictionary<string, string>	A sequence of key-value pairs representing (oldName, newName).
strict	bool (optional)	If true, an error is raised if any column in mapping is not found in the schema. If false, columns that are not found are silently ignored. Default is true.

---

Reverse

Reverse the LazyFrame.

member Reverse : unit -> LazyFrame

---

RowsAsync

Streams LazyFrame rows asynchronously as strongly-typed F# Records/Tuples/DTOs. Serves as the asynchronous counterpart to DataFrame.Rows<'T>().

member RowsAsync(
    ?chunkSize: int64,
    ?engine: Engine,
    ?maintainOrder: bool,
    ?cancellationToken: CancellationToken
) : IAsyncEnumerable<'T>

Parameters

Name	Type	Description
chunkSize	int64 (optional)	-
engine	Engine (optional)	-
maintainOrder	bool (optional)	-
cancellationToken	CancellationToken (optional)	-

---

Select

Select columns from the lazyframe using a sequence of column expressions.

Select columns from the lazyframe using a selector.

member Select(expr: Expr) : LazyFrame
member Select(selector: Selector) : LazyFrame
member Select(exprs: seq<Expr>) : LazyFrame
member Select(columns: seq<'a>) : LazyFrame

Parameters

Name	Type	Description
expr	Expr	-
selector	Selector	-
exprs	seq<Expr>	-
columns	seq<'a>	-

---

SetSorted

Mark one or multiple columns as sorted. This is an optimizer hint and will not actually execute a sorting operation.

member SetSorted(columns: Selector, ?descending: bool, ?nullsLast: bool) : LazyFrame

Parameters

Name	Type	Description
columns	Selector	The columns to mark as sorted. Accepts strings, arrays, or Selectors (e.g. Cs.Temporal()).
descending	bool (optional)	Whether the columns are sorted in descending order.
nullsLast	bool (optional)	Whether null values appear last.

Returns: A new LazyFrame with the sorted hints applied to the query plan.

---

Show

Print the LazyFrame to Console (Stdout).

member Show : unit -> unit

---

SinkBatches

Stream the query result in batches. This executes the query and calls 'onBatch' for each RecordBatch produced.

member SinkBatches(onBatch: Action<RecordBatch>) : unit

Parameters

Name	Type	Description
onBatch	Action<RecordBatch>	-

---

SinkCatalogTable

Sinks the LazyFrame to a Unity Catalog table.

member SinkCatalogTable(
    catalog: UnityCatalog,
    catalogName: string,
    schemaName: string,
    tableName: string,
    ?partitionBy: Selector,
    ?mode: DeltaSaveMode,
    ?canEvolve: bool,
    ?includeKeys: bool,
    ?keysPreGrouped: bool,
    ?maxRowsPerFile: int,
    ?approxBytesPerFile: int64,
    ?compression: ParquetCompression,
    ?compressionLevel: int,
    ?statistics: bool,
    ?rowGroupSize: uint32,
    ?dataPageSize: uint32,
    ?compatLevel: int,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
catalog	UnityCatalog	-
catalogName	string	-
schemaName	string	-
tableName	string	-
partitionBy	Selector (optional)	-
mode	DeltaSaveMode (optional)	-
canEvolve	bool (optional)	-
includeKeys	bool (optional)	-
keysPreGrouped	bool (optional)	-
maxRowsPerFile	int (optional)	-
approxBytesPerFile	int64 (optional)	-
compression	ParquetCompression (optional)	-
compressionLevel	int (optional)	-
statistics	bool (optional)	-
rowGroupSize	uint32 (optional)	-
dataPageSize	uint32 (optional)	-
compatLevel	int (optional)	-
maintainOrder	bool (optional)	-
syncOnClose	SyncOnClose (optional)	-
mkdir	bool (optional)	-
cloudOptions	CloudOptions (optional)	-

---

SinkCsv

Execute the LazyFrame and sink the result to a CSV file.

This operation allows processing datasets larger than memory by streaming results directly to the file system.

member SinkCsv(
    path: string,
    ?includeHeader: bool,
    ?includeBom: bool,
    ?separator: char,
    ?quoteChar: char,
    ?quoteStyle: QuoteStyle,
    ?nullValue: string,
    ?lineTerminator: string,
    ?floatScientific: bool,
    ?floatPrecision: int,
    ?decimalComma: bool,
    ?dateFormat: string,
    ?timeFormat: string,
    ?datetimeFormat: string,
    ?checkExtension: bool,
    ?compression: ExternalCompression,
    ?compressionLevel: int,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?batchSize: int,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	-
includeHeader	bool (optional)	-
includeBom	bool (optional)	-
separator	char (optional)	-
quoteChar	char (optional)	-
quoteStyle	QuoteStyle (optional)	-
nullValue	string (optional)	-
lineTerminator	string (optional)	-
floatScientific	bool (optional)	-
floatPrecision	int (optional)	-
decimalComma	bool (optional)	-
dateFormat	string (optional)	-
timeFormat	string (optional)	-
datetimeFormat	string (optional)	-
checkExtension	bool (optional)	-
compression	ExternalCompression (optional)	-
compressionLevel	int (optional)	-
maintainOrder	bool (optional)	-
syncOnClose	SyncOnClose (optional)	-
mkdir	bool (optional)	-
batchSize	int (optional)	-
cloudOptions	CloudOptions (optional)	-

---

SinkCsvMemory

Sink the LazyFrame to a CSV format in memory.

This allows for streaming execution directly into a byte array without writing to disk.

member SinkCsvMemory(
    ?includeBom: bool,
    ?includeHeader: bool,
    ?batchSize: int,
    ?checkExtension: bool,
    ?compressionCode: ExternalCompression,
    ?compressionLevel: int,
    ?dateFormat: string,
    ?timeFormat: string,
    ?datetimeFormat: string,
    ?floatScientific: int,
    ?floatPrecision: int,
    ?decimalComma: bool,
    ?separator: byte,
    ?quoteChar: byte,
    ?nullValue: string,
    ?lineTerminator: string,
    ?quoteStyle: QuoteStyle,
    ?maintainOrder: bool
) : byte[]

Parameters

Name	Type	Description
includeBom	bool (optional)	-
includeHeader	bool (optional)	-
batchSize	int (optional)	-
checkExtension	bool (optional)	-
compressionCode	ExternalCompression (optional)	-
compressionLevel	int (optional)	-
dateFormat	string (optional)	-
timeFormat	string (optional)	-
datetimeFormat	string (optional)	-
floatScientific	int (optional)	-
floatPrecision	int (optional)	-
decimalComma	bool (optional)	-
separator	byte (optional)	-
quoteChar	byte (optional)	-
nullValue	string (optional)	-
lineTerminator	string (optional)	-
quoteStyle	QuoteStyle (optional)	-
maintainOrder	bool (optional)	-

Returns: A byte array containing the serialized CSV data.

---

SinkCsvPartitioned

Execute the LazyFrame and sink the result to a CSV file, partitioned by the given selector.

member SinkCsvPartitioned(
    path: string,
    partitionBy: Selector,
    ?includeKeys: bool,
    ?keysPreGrouped: bool,
    ?maxRowsPerFile: int,
    ?approxBytesPerFile: int64,
    ?includeHeader: bool,
    ?includeBom: bool,
    ?separator: char,
    ?quoteChar: char,
    ?quoteStyle: QuoteStyle,
    ?nullValue: string,
    ?lineTerminator: string,
    ?floatScientific: bool,
    ?floatPrecision: int,
    ?decimalComma: bool,
    ?dateFormat: string,
    ?timeFormat: string,
    ?datetimeFormat: string,
    ?checkExtension: bool,
    ?compression: ExternalCompression,
    ?compressionLevel: int,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?batchSize: int,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	-
partitionBy	Selector	-
includeKeys	bool (optional)	-
keysPreGrouped	bool (optional)	-
maxRowsPerFile	int (optional)	-
approxBytesPerFile	int64 (optional)	-
includeHeader	bool (optional)	-
includeBom	bool (optional)	-
separator	char (optional)	-
quoteChar	char (optional)	-
quoteStyle	QuoteStyle (optional)	-
nullValue	string (optional)	-
lineTerminator	string (optional)	-
floatScientific	bool (optional)	-
floatPrecision	int (optional)	-
decimalComma	bool (optional)	-
dateFormat	string (optional)	-
timeFormat	string (optional)	-
datetimeFormat	string (optional)	-
checkExtension	bool (optional)	-
compression	ExternalCompression (optional)	-
compressionLevel	int (optional)	-
maintainOrder	bool (optional)	-
syncOnClose	SyncOnClose (optional)	-
mkdir	bool (optional)	-
batchSize	int (optional)	-
cloudOptions	CloudOptions (optional)	-

---

SinkDelta

Sink the LazyFrame to a Delta Lake table with partition discovery.

This operation performs a "blind write" of partitioned Parquet files (Hive-style) and then commits a transaction to the Delta Log, registering the new files.

member SinkDelta(
    path: string,
    ?partitionBy: Selector,
    ?mode: DeltaSaveMode,
    ?canEvolve: bool,
    ?includeKeys: bool,
    ?keysPreGrouped: bool,
    ?maxRowsPerFile: int,
    ?approxBytesPerFile: int64,
    ?compression: ParquetCompression,
    ?compressionLevel: int,
    ?statistics: bool,
    ?rowGroupSize: uint32,
    ?dataPageSize: uint32,
    ?compatLevel: int,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	Path to the root of the Delta Table. Can be local (e.g. "./data/table") or remote (e.g. "s3://bucket/table").
partitionBy	Selector (optional)	The selector(s) to partition the data by. Directories will be created in the format "col=value".
mode	DeltaSaveMode (optional)	Save mode (Append, Overwrite, ErrorIfExists, Ignore). Default is Append.
canEvolve	bool (optional)	-
includeKeys	bool (optional)	Whether to include the partition keys in the Parquet files themselves. Default is true (recommended for Delta Lake compatibility).
keysPreGrouped	bool (optional)	Assert that the keys are already pre-grouped. This can speed up the operation if true.
maxRowsPerFile	int (optional)	Maximum number of rows per file. 0 means no limit.
approxBytesPerFile	int64 (optional)	Approximate size in bytes per file. 0 means no limit.
compression	ParquetCompression (optional)	Compression codec to use (Snappy, Zstd, etc.).
compressionLevel	int (optional)	Compression level (depends on the codec).
statistics	bool (optional)	Write statistics to the Parquet file. Delta Lake uses these stats for data skipping, so 'true' is highly recommended.
rowGroupSize	uint32 (optional)	Target row group size (in rows).
dataPageSize	uint32 (optional)	Target data page size (in bytes).
compatLevel	int (optional)	IPC format compatibility.
maintainOrder	bool (optional)	Maintain the order of the data.
syncOnClose	SyncOnClose (optional)	Whether to sync the file to disk on close.
mkdir	bool (optional)	Create parent directories if they don't exist.
cloudOptions	CloudOptions (optional)	Options for cloud storage authentication and configuration.

---

SinkIpc

Sink the LazyFrame to an IPC (Arrow) file.

This allows for streaming execution.

member SinkIpc(
    path: string,
    ?compression: IpcCompression,
    ?compatLevel: int,
    ?recordBatchSize: int,
    ?recordBatchStatistics: bool,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	Output file path.
compression	IpcCompression (optional)	Compression method (NoCompression, LZ4, ZSTD). Defaults to NoCompression.
compatLevel	int (optional)	Arrow compatibility level. -1 means newest. Defaults to -1.
recordBatchSize	int (optional)	Number of rows per record batch (0 = default).
recordBatchStatistics	bool (optional)	Write statistics to the record batch header. Defaults to true.
maintainOrder	bool (optional)	Whether to maintain the order of the data. Defaults to true.
syncOnClose	SyncOnClose (optional)	File synchronization behavior on close. Defaults to None.
mkdir	bool (optional)	Recursively create the directory if it does not exist. Defaults to false.
cloudOptions	CloudOptions (optional)	Options for cloud storage.

---

SinkIpcMemory

Sink the LazyFrame to an IPC (Arrow) format in memory.

This allows for streaming execution directly into a byte array without writing to disk.

member SinkIpcMemory(
    ?compression: IpcCompression,
    ?compatLevel: int,
    ?recordBatchSize: int,
    ?recordBatchStatistics: bool,
    ?maintainOrder: bool
) : byte[]

Parameters

Name	Type	Description
compression	IpcCompression (optional)	-
compatLevel	int (optional)	-
recordBatchSize	int (optional)	-
recordBatchStatistics	bool (optional)	-
maintainOrder	bool (optional)	-

---

SinkIpcPartitioned

Sink the LazyFrame to an IPC (Arrow) file, partitioned by the given selector.

member SinkIpcPartitioned(
    path: string,
    partitionBy: Selector,
    ?includeKeys: bool,
    ?keysPreGrouped: bool,
    ?maxRowsPerFile: int,
    ?approxBytesPerFile: int64,
    ?compression: IpcCompression,
    ?compatLevel: int,
    ?recordBatchSize: int,
    ?recordBatchStatistics: bool,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	-
partitionBy	Selector	The selector(s) to partition the data by.
includeKeys	bool (optional)	Whether to include the partition keys in the output files.
keysPreGrouped	bool (optional)	Assert that the keys are already pre-grouped. This can speed up the operation if true. Use with caution: if the data is not grouped, the output may be incorrect.
maxRowsPerFile	int (optional)	Maximum number of rows per file. 0 means no limit.
approxBytesPerFile	int64 (optional)	Approximate size in bytes per file. 0 means no limit.
compression	IpcCompression (optional)	-
compatLevel	int (optional)	-
recordBatchSize	int (optional)	-
recordBatchStatistics	bool (optional)	-
maintainOrder	bool (optional)	-
syncOnClose	SyncOnClose (optional)	-
mkdir	bool (optional)	-
cloudOptions	CloudOptions (optional)	-

---

SinkJson

Sink the LazyFrame to a NDJSON (Newline Delimited JSON) file.

member SinkJson(
    path: string,
    ?compression: ExternalCompression,
    ?compressionLevel: int,
    ?checkExtension: bool,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	Output file path.
compression	ExternalCompression (optional)	Compression method (Gzip/Zstd).
compressionLevel	int (optional)	Compression level.
checkExtension	bool (optional)	Whether to check if the file extension matches '.json' or '.ndjson'.
maintainOrder	bool (optional)	Maintain the order of data.
syncOnClose	SyncOnClose (optional)	Sync to disk on close.
mkdir	bool (optional)	Create parent directories.
cloudOptions	CloudOptions (optional)	Cloud storage options.

---

SinkJsonMemory

Sink the LazyFrame to a NDJSON (Newline Delimited JSON) format in memory.

member SinkJsonMemory(
    ?compression: ExternalCompression,
    ?compressionLevel: int,
    ?checkExtension: bool,
    ?maintainOrder: bool
) : byte[]

Parameters

Name	Type	Description
compression	ExternalCompression (optional)	-
compressionLevel	int (optional)	-
checkExtension	bool (optional)	-
maintainOrder	bool (optional)	-

Returns: A byte array containing the serialized NDJSON data.

---

SinkJsonPartitioned

Sink the LazyFrame to a NDJSON (Newline Delimited JSON) file, partitioned by the given selector.

member SinkJsonPartitioned(
    path: string,
    partitionBy: Selector,
    ?includeKeys: bool,
    ?keysPreGrouped: bool,
    ?maxRowsPerFile: int,
    ?approxBytesPerFile: int64,
    ?compression: ExternalCompression,
    ?compressionLevel: int,
    ?checkExtension: bool,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	-
partitionBy	Selector	-
includeKeys	bool (optional)	-
keysPreGrouped	bool (optional)	-
maxRowsPerFile	int (optional)	-
approxBytesPerFile	int64 (optional)	-
compression	ExternalCompression (optional)	-
compressionLevel	int (optional)	-
checkExtension	bool (optional)	-
maintainOrder	bool (optional)	-
syncOnClose	SyncOnClose (optional)	-
mkdir	bool (optional)	-
cloudOptions	CloudOptions (optional)	-

---

SinkNdJson

Alias for SinkJson (Lazily evaluated JSON is always NDJSON/JsonLines).

member SinkNdJson(
    path: string,
    ?compression: ExternalCompression,
    ?compressionLevel: int,
    ?checkExtension: bool,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	-
compression	ExternalCompression (optional)	-
compressionLevel	int (optional)	-
checkExtension	bool (optional)	-
maintainOrder	bool (optional)	-
syncOnClose	SyncOnClose (optional)	-
mkdir	bool (optional)	-
cloudOptions	CloudOptions (optional)	-

---

SinkParquet

Sink the LazyFrame to a Parquet file.

This allows for streaming execution, processing the data in chunks and writing it to the file without loading the entire dataset into memory.

member SinkParquet(
    path: string,
    ?compression: ParquetCompression,
    ?compressionLevel: int,
    ?statistics: bool,
    ?rowGroupSize: int,
    ?dataPageSize: int,
    ?compatLevel: int,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	Path to the output file.
compression	ParquetCompression (optional)	Compression codec to use.
compressionLevel	int (optional)	Compression level (depends on the codec).
statistics	bool (optional)	Write statistics to the parquet file.
rowGroupSize	int (optional)	Target row group size (in rows).
dataPageSize	int (optional)	Target data page size (in bytes).
compatLevel	int (optional)	IPC format compatibility, -1: oldest, 0: default, 1: newest.
maintainOrder	bool (optional)	Maintain the order of the data.
syncOnClose	SyncOnClose (optional)	Whether to sync the file to disk on close.
mkdir	bool (optional)	Create parent directories if they don't exist (Local file system only).
cloudOptions	CloudOptions (optional)	Options for cloud storage (AWS S3, Azure Blob, GCS, etc.).

---

SinkParquetMemory

Sink the LazyFrame to a Parquet format in memory.

This allows for streaming execution directly into a byte array without writing to disk.

member SinkParquetMemory(
    ?compression: ParquetCompression,
    ?compressionLevel: int,
    ?statistics: bool,
    ?rowGroupSize: int,
    ?dataPageSize: int,
    ?compatLevel: int,
    ?maintainOrder: bool
) : byte[]

Parameters

Name	Type	Description
compression	ParquetCompression (optional)	-
compressionLevel	int (optional)	-
statistics	bool (optional)	-
rowGroupSize	int (optional)	-
dataPageSize	int (optional)	-
compatLevel	int (optional)	-
maintainOrder	bool (optional)	-

Returns: A byte array containing the serialized Parquet data.

---

SinkParquetPartitioned

Sink the LazyFrame to a set of Parquet files, partitioned by the specified selector.

This writes the dataset to a directory, splitting the data into multiple files based on the partition key(s) defined in partitionBy.

member SinkParquetPartitioned(
    path: string,
    partitionBy: Selector,
    ?includeKeys: bool,
    ?keysPreGrouped: bool,
    ?maxRowsPerFile: int,
    ?approxBytesPerFile: int64,
    ?compression: ParquetCompression,
    ?compressionLevel: int,
    ?statistics: bool,
    ?rowGroupSize: int,
    ?dataPageSize: int,
    ?compatLevel: int,
    ?maintainOrder: bool,
    ?syncOnClose: SyncOnClose,
    ?mkdir: bool,
    ?cloudOptions: CloudOptions
) : unit

Parameters

Name	Type	Description
path	string	-
partitionBy	Selector	-
includeKeys	bool (optional)	-
keysPreGrouped	bool (optional)	-
maxRowsPerFile	int (optional)	-
approxBytesPerFile	int64 (optional)	-
compression	ParquetCompression (optional)	-
compressionLevel	int (optional)	-
statistics	bool (optional)	-
rowGroupSize	int (optional)	-
dataPageSize	int (optional)	-
compatLevel	int (optional)	-
maintainOrder	bool (optional)	-
syncOnClose	SyncOnClose (optional)	-
mkdir	bool (optional)	-
cloudOptions	CloudOptions (optional)	-

---

SinkTo

Stream query results directly to a database or other IDataReader consumer. Uses a producer-consumer pattern with bounded capacity for memory efficiency.

member SinkTo(writerAction: Action<IDataReader>, ?bufferSize: int, ?typeOverrides: IDictionary<string, Type>) : unit

Parameters

Name	Type	Description
writerAction	Action<IDataReader>	Callback to consume the IDataReader (e.g., using SqlBulkCopy).
bufferSize	int (optional)	Max number of batches to buffer in memory (default: 5).
typeOverrides	IDictionary<string, Type> (optional)	Force specific C# types for columns (e.g. map Date32 to DateTime).

---

Slice

Slice the LazyFrame along the rows. If length is omitted, it slices to the end of the LazyFrame.

member Slice(offset: int64, ?length: uint32) : LazyFrame

Parameters

Name	Type	Description
offset	int64	-
length	uint32 (optional)	-

---

Sort

member Sort(
    columns: seq<IColumnExpr>,
    descending: seq<bool>,
    nullsLast: seq<bool>,
    ?maintainOrder: bool
) : LazyFrame

member Sort(
    columns: seq<Expr>,
    descending: seq<bool>,
    nullsLast: seq<bool>,
    ?maintainOrder: bool
) : LazyFrame

member Sort(
    columns: seq<IColumnExpr>,
    ?descending: bool,
    ?nullsLast: bool,
    ?maintainOrder: bool
) : LazyFrame

member Sort(
    columns: seq<Expr>,
    ?descending: bool,
    ?nullsLast: bool,
    ?maintainOrder: bool
) : LazyFrame

member Sort(expr: Expr, ?descending: bool, ?nullsLast: bool) : LazyFrame
member Sort(colName: string, ?descending: bool, ?nullsLast: bool) : LazyFrame

Parameters

Name	Type	Description
columns	seq<IColumnExpr> / seq<Expr>	-
descending	seq<bool> / bool (optional)	-
nullsLast	seq<bool> / bool (optional)	-
maintainOrder	bool (optional)	-
expr	Expr	-
colName	string	-

---

Std

Aggregate the columns in the Frame to their standard deviation value.

member Std(?ddof: byte) : LazyFrame

Parameters

Name	Type	Description
ddof	byte (optional)	“Delta Degrees of Freedom”: the divisor used in the calculation is N - ddof, where N represents the number of elements. By default ddof is 1.

---

Sum

Aggregate the columns in the Frame to their sum value.

member Sum : unit -> LazyFrame

---

Tail

member Tail(?n: uint32) : LazyFrame

Parameters

Name	Type	Description
n	uint32 (optional)	-

---

ToAsyncEnumerable

Executes the LazyFrame via native streaming batch engine, yielding strongly typed F# Records/Tuples/DTOs with O(batch) memory overhead and pull-based backpressure.

member ToAsyncEnumerable(
    ?chunkSize: int64,
    ?engine: Engine,
    ?maintainOrder: bool,
    ?cancellationToken: CancellationToken
) : IAsyncEnumerable<'T>

Parameters

Name	Type	Description
chunkSize	int64 (optional)	Maximum row count per native batch (0 uses Polars default batch size).
engine	Engine (optional)	Execution engine selection.
maintainOrder	bool (optional)	Whether to enforce deterministic row ordering across batches.
cancellationToken	CancellationToken (optional)	Optional cooperative cancellation token.

Returns: An asynchronous stream of hydrated F# row items.

---

ToHtml

Generates an HTML visualization of the LazyFrame execution plan and schema for LINQPad.

member ToHtml(?optimized: bool) : string

Parameters

Name	Type	Description
optimized	bool (optional)	Whether to explain the optimized logical plan.

Returns: An HTML representation formatted with monospace styling.

---

TopK

Get the top k rows based on the given columns. This is often faster than a full sort followed by a head.

member TopK(k: int, by: seq<'a>, ?reverse: seq<bool>) : LazyFrame
member TopK(k: int, by: seq<'a>, reverse: bool) : LazyFrame

Parameters

Name	Type	Description
k	int	Number of rows to return.
by	seq<'a>	Columns to sort by.
reverse	seq<bool> (optional)	Sort direction per column. Default is false (no reverse).

---

Unique

Keep unique rows (stable) based on a subset of columns defined by a Selector.

Keep unique rows based on specific column names.

member Unique(?subset: Selector, ?keep: UniqueKeepStrategy, ?maintainOrder: bool) : LazyFrame
member Unique(columns: seq<string>, ?keep: UniqueKeepStrategy, ?maintainOrder: bool) : LazyFrame

Parameters

Name	Type	Description
subset	Selector (optional)	-
keep	UniqueKeepStrategy (optional)	-
maintainOrder	bool (optional)	-
columns	seq<string>	-

---

Unnest

Decompose a struct column into multiple columns.

Helper: Unnest columns by name.

Helper: Unnest a single column by name.

member Unnest(selector: Selector, ?separator: string) : LazyFrame
member Unnest(columns: seq<string>, ?separator: string) : LazyFrame
member Unnest(column: string, ?separator: string) : LazyFrame

Parameters

Name	Type	Description
selector	Selector	-
separator	string (optional)	-
columns	seq<string>	-
column	string	-

---

Unpivot

Unpivot (Melt) the LazyFrame using Selectors. Primary overload backed by native binding.

Unpivot (Melt) overload for simple string lists. Auto-converts to Selectors.

member Unpivot(
    index: Selector,
    on: Selector,
    ?variableName: string,
    ?valueName: string
) : LazyFrame

member Unpivot(
    index: seq<string>,
    on: seq<string>,
    ?variableName: string,
    ?valueName: string
) : LazyFrame

Parameters

Name	Type	Description
index	Selector / seq<string>	-
on	Selector / seq<string>	-
variableName	string (optional)	-
valueName	string (optional)	-

---

Update

member Update(
    other: LazyFrame,
    ?on: IColumnExpr,
    ?how: JoinType,
    ?leftOn: IColumnExpr,
    ?rightOn: IColumnExpr,
    ?includeNulls: bool,
    ?maintainOrder: JoinMaintainOrder
) : LazyFrame

Parameters

Name	Type	Description
other	LazyFrame	-
on	IColumnExpr (optional)	-
how	JoinType (optional)	-
leftOn	IColumnExpr (optional)	-
rightOn	IColumnExpr (optional)	-
includeNulls	bool (optional)	-
maintainOrder	JoinMaintainOrder (optional)	-

---

Var

Aggregate the columns in the Frame to their variance value.

member Var(?ddof: byte) : LazyFrame

Parameters

Name	Type	Description
ddof	byte (optional)	“Delta Degrees of Freedom”: the divisor used in the calculation is N - ddof, where N represents the number of elements. By default ddof is 1.

---

WithColumns

Add or replace a single column in the LazyFrame.

Add or replace multiple columns in the LazyFrame.

Add or replace columns using generic column expressions (Expr or Selectors).

member WithColumns(expr: Expr) : LazyFrame
member WithColumns(exprs: seq<Expr>) : LazyFrame
member WithColumns(columns: seq<'a>) : LazyFrame

Parameters

Name	Type	Description
expr	Expr	The expression defining the new column.
exprs	seq<Expr>	List of expressions defining the new columns.
columns	seq<'a>	-

---

WithRowIndex

Add a column at index 0 that counts the rows.

This can be useful to generate a unique index or to maintain order in operations that would otherwise discard it.

member WithRowIndex(?name: string, ?offset: int) : LazyFrame

Parameters

Name	Type	Description
name	string (optional)	The name of the new row index column. Defaults to "index".
offset	int (optional)	The starting value of the row index. Defaults to 0.

Returns: A new LazyFrame with the row index column added.

---

Pipeline Module Functions (LazyFrame.*)

LazyFrame.agg

Aggregate LazyGroupBy.

LazyFrame.agg : aggs: seq<Expr> -> builder: LazyGroupBy -> LazyFrame

Parameters

Name	Type	Description
aggs	seq<Expr>	-
builder	LazyGroupBy	-

---

LazyFrame.collect

Collect the LazyFrame using the default engine.

LazyFrame.collect : lazyFrame: LazyFrame -> DataFrame

Parameters

Name	Type	Description
lazyFrame	LazyFrame	-

---

LazyFrame.collectAsync

Asynchronously execute the LazyFrame query plan. Useful for keeping UI responsive during heavy calculations.

LazyFrame.collectAsync : lf: LazyFrame -> FSharpAsync<DataFrame>

Parameters

Name	Type	Description
lf	LazyFrame	-

---

LazyFrame.collectBatchesAsync

Streams materialized DataFrame batches asynchronously.

LazyFrame.collectBatchesAsync : chunkSize: int64 -> lf: LazyFrame -> IAsyncEnumerable<DataFrame>

Parameters

Name	Type	Description
chunkSize	int64	-
lf	LazyFrame	-

---

LazyFrame.collectSchema

Get the schema of the LazyFrame.

LazyFrame.collectSchema : lf: LazyFrame -> PolarsSchema

Parameters

Name	Type	Description
lf	LazyFrame	-

---

LazyFrame.collectWithEngine

Collect the LazyFrame using the specified engine.

LazyFrame.collectWithEngine : engine: Engine -> lazyFrame: LazyFrame -> DataFrame

Parameters

Name	Type	Description
engine	Engine	-
lazyFrame	LazyFrame	-

---

LazyFrame.concatDiagonal

Concatenate multiple LazyFrames diagonally.

LazyFrame.concatDiagonal : lfs: seq<LazyFrame> -> LazyFrame

Parameters

Name	Type	Description
lfs	seq<LazyFrame>	-

---

LazyFrame.concatHorizontal

Concatenate multiple LazyFrames horizontally.

LazyFrame.concatHorizontal : lfs: seq<LazyFrame> -> LazyFrame

Parameters

Name	Type	Description
lfs	seq<LazyFrame>	-

---

LazyFrame.concatVertical

Concatenate multiple LazyFrames vertically.

LazyFrame.concatVertical : lfs: seq<LazyFrame> -> LazyFrame

Parameters

Name	Type	Description
lfs	seq<LazyFrame>	-

---

LazyFrame.drop

Drop columns from the LazyFrame.

LazyFrame.drop : columns: 'a -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
columns	'a	-
lf	LazyFrame	-

---

LazyFrame.dropNans

Drop NaN values from the LazyFrame.

LazyFrame.dropNans : lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
lf	LazyFrame	-

---

LazyFrame.dropNansOn

Drop NaN values from the LazyFrame with specific subset.

LazyFrame.dropNansOn : subset: 'a -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
subset	'a	-
lf	LazyFrame	-

---

LazyFrame.dropNulls

Drop null values from the LazyFrame.

LazyFrame.dropNulls : lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
lf	LazyFrame	-

---

LazyFrame.dropNullsOn

Drop null values from the LazyFrame with specific subset.

LazyFrame.dropNullsOn : subset: Expr -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
subset	Expr	-
lf	LazyFrame	-

---

LazyFrame.explain

Explain the execution plan of the LazyFrame.

LazyFrame.explain : lazyFrame: LazyFrame -> string

Parameters

Name	Type	Description
lazyFrame	LazyFrame	-

---

LazyFrame.explainUnoptimized

Explain the unoptimized LazyFrame execution plan.

LazyFrame.explainUnoptimized : lf: LazyFrame -> string

Parameters

Name	Type	Description
lf	LazyFrame	-

---

LazyFrame.fillNan

Fill NaN values in all columns with a specified value.

LazyFrame.fillNan : fillValue: Expr -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
fillValue	Expr	-
lf	LazyFrame	-

---

LazyFrame.fillNull

Fill null values in all columns with a specified value.

LazyFrame.fillNull : fillValue: Expr -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
fillValue	Expr	-
lf	LazyFrame	-

---

LazyFrame.filter

Filter rows based on a boolean expression.

LazyFrame.filter : expr: Expr -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
expr	Expr	-
lf	LazyFrame	-

---

LazyFrame.filterAll

Filter frame rows by combining multiple predicates with logical AND.

LazyFrame.filterAll : predicates: seq<Expr> -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
predicates	seq<Expr>	-
lf	LazyFrame	-

---

LazyFrame.groupBy

Group by keys.

LazyFrame.groupBy : keys: seq<Expr> -> lf: LazyFrame -> LazyGroupBy

Parameters

Name	Type	Description
keys	seq<Expr>	-
lf	LazyFrame	-

---

LazyFrame.having

Having clause for LazyGroupBy.

LazyFrame.having : predicate: Expr -> builder: LazyGroupBy -> LazyGroupBy

Parameters

Name	Type	Description
predicate	Expr	-
builder	LazyGroupBy	-

---

LazyFrame.head

Get the head of the LazyFrame.

LazyFrame.head : n: int -> lazyFrame: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
n	int	-
lazyFrame	LazyFrame	-

---

LazyFrame.join

Perform a join between two LazyFrames using join keys.

LazyFrame.join : other: LazyFrame -> leftOn: seq<Expr> -> rightOn: seq<Expr> -> how: JoinType -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
other	LazyFrame	-
leftOn	seq<Expr>	-
rightOn	seq<Expr>	-
how	JoinType	-
lf	LazyFrame	-

---

LazyFrame.joinOn

Perform a join between two LazyFrames.

LazyFrame.joinOn : other: LazyFrame -> on: seq<Expr> -> how: JoinType -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
other	LazyFrame	-
on	seq<Expr>	-
how	JoinType	-
lf	LazyFrame	-

---

LazyFrame.melt

Alias for LazyFrame.unpivot.

LazyFrame.melt : index: Selector -> on: Selector -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
index	Selector	-
on	Selector	-
lf	LazyFrame	-

---

LazyFrame.meltNamed

Alias for LazyFrame.unpivotNamed.

LazyFrame.meltNamed : index: Selector -> on: Selector -> variableName: string -> valueName: string -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
index	Selector	-
on	Selector	-
variableName	string	-
valueName	string	-
lf	LazyFrame	-

---

LazyFrame.ofEager

Create a LazyFrame from DataFrame

LazyFrame.ofEager : df: DataFrame -> LazyFrame

Parameters

Name	Type	Description
df	DataFrame	-

---

LazyFrame.orderByAscending

Alias for sortAscending.

LazyFrame.orderByAscending : expr: seq<Expr> -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
expr	seq<Expr>	-
lf	LazyFrame	-

---

LazyFrame.orderByDescending

Alias for sortDescending.

LazyFrame.orderByDescending : expr: seq<Expr> -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
expr	seq<Expr>	-
lf	LazyFrame	-

---

LazyFrame.rename

Rename columns based on a mapping dictionary or key-value pairs.

LazyFrame.rename : mapping: seq<(string * string)> -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
mapping	seq<(string * string)>	-
lf	LazyFrame	-

---

LazyFrame.reverse

Reverse the order of the LazyFrame.

LazyFrame.reverse : lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
lf	LazyFrame	-

---

LazyFrame.select

Select columns from LazyFrame.

LazyFrame.select : exprs: seq<'a> -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
exprs	seq<'a>	-
lf	LazyFrame	-

---

LazyFrame.slice

Slice rows starting at offset with length.

LazyFrame.slice : offset: int64 -> length: uint32 -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
offset	int64	-
length	uint32	-
lf	LazyFrame	-

---

LazyFrame.sortAscending

Sort (Order By) the LazyFrame.

LazyFrame.sortAscending : exprs: seq<Expr> -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
exprs	seq<Expr>	-
lf	LazyFrame	-

---

LazyFrame.sortDescending

Sort (Order By) the LazyFrame in descending order.

LazyFrame.sortDescending : exprs: seq<Expr> -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
exprs	seq<Expr>	-
lf	LazyFrame	-

---

LazyFrame.tail

Get the tail of the LazyFrame.

LazyFrame.tail : n: uint32 -> lazyFrame: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
n	uint32	-
lazyFrame	LazyFrame	-

---

LazyFrame.toAsyncEnumerable

Streams strongly typed F# Records/Tuples/DTOs asynchronously from a LazyFrame.

LazyFrame.toAsyncEnumerable : chunkSize: int64 -> lf: LazyFrame -> IAsyncEnumerable<'T>

Parameters

Name	Type	Description
chunkSize	int64	-
lf	LazyFrame	-

---

LazyFrame.toRowsAsync

Streams strongly typed F# Records/Tuples/DTOs asynchronously from a LazyFrame.

LazyFrame.toRowsAsync : chunkSize: int64 -> lf: LazyFrame -> IAsyncEnumerable<'T>

Parameters

Name	Type	Description
chunkSize	int64	-
lf	LazyFrame	-

---

LazyFrame.unnest

Decompose multiple struct columns.

LazyFrame.unnest : columns: 'a -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
columns	'a	-
lf	LazyFrame	-

---

LazyFrame.unpivot

Unpivot (Melt) the LazyFrame from wide to long format using Selectors. Default column names ("variable", "value") will be used.

LazyFrame.unpivot : index: Selector -> on: Selector -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
index	Selector	-
on	Selector	-
lf	LazyFrame	-

---

LazyFrame.unpivotNamed

Unpivot (Melt) the LazyFrame using Selectors with custom variable and value column names.

LazyFrame.unpivotNamed : index: Selector -> on: Selector -> variableName: string -> valueName: string -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
index	Selector	-
on	Selector	-
variableName	string	-
valueName	string	-
lf	LazyFrame	-

---

LazyFrame.withColumn

Add or replace columns in the LazyFrame.

LazyFrame.withColumn : expr: Expr -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
expr	Expr	-
lf	LazyFrame	-

---

LazyFrame.withColumns

Add or replace multiple columns in the LazyFrame.

LazyFrame.withColumns : exprs: seq<Expr> -> lf: LazyFrame -> LazyFrame

Parameters

Name	Type	Description
exprs	seq<Expr>	-
lf	LazyFrame	-

---