datafusion-python/python/datafusion/expr.py at main · ongchi/datafusion-python · GitHub

History

787 lines (638 loc) · 26.8 KB

Raw

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

463

464

465

466

467

468

469

470

471

472

473

474

475

476

477

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

498

499

500

501

502

503

504

505

506

507

508

509

510

511

512

513

514

515

516

517

518

519

520

521

522

523

524

525

526

527

528

529

530

531

532

533

534

535

536

537

538

539

540

541

542

543

544

545

546

547

548

549

550

551

552

553

554

555

556

557

558

559

560

561

562

563

564

565

566

567

568

569

570

571

572

573

574

575

576

577

578

579

580

581

582

583

584

585

586

587

588

589

590

591

592

593

594

595

596

597

598

599

600

601

602

603

604

605

606

607

608

609

610

611

612

613

614

615

616

617

618

619

620

621

622

623

624

625

626

627

628

629

630

631

632

633

634

635

636

637

638

639

640

641

642

643

644

645

646

647

648

649

650

651

652

653

654

655

656

657

658

659

660

661

662

663

664

665

666

667

668

669

670

671

672

673

674

675

676

677

678

679

680

681

682

683

684

685

686

687

688

689

690

691

692

693

694

695

696

697

698

699

700

701

702

703

704

705

706

707

708

709

710

711

712

713

714

715

716

717

718

719

720

721

722

723

724

725

726

727

728

729

730

731

732

733

734

735

736

737

738

739

740

741

742

743

744

745

746

747

748

749

750

751

752

753

754

755

756

757

758

759

760

761

762

763

764

765

766

767

768

769

770

771

772

773

774

775

776

777

778

779

780

781

782

783

784

785

786

787

# Licensed to the Apache Software Foundation (ASF) under one

# or more contributor license agreements. See the NOTICE file

# distributed with this work for additional information

# regarding copyright ownership. The ASF licenses this file

# to you under the Apache License, Version 2.0 (the

# "License"); you may not use this file except in compliance

# with the License. You may obtain a copy of the License at

# http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing,

# software distributed under the License is distributed on an

# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

# KIND, either express or implied. See the License for the

# specific language governing permissions and limitations

# under the License.

"""This module supports expressions, one of the core concepts in DataFusion.

See :ref:`Expressions` in the online documentation for more details.

"""

from __future__ import annotations

from typing import Any, Optional, Type, TYPE_CHECKING

import pyarrow as pa

from datafusion.common import DataTypeMap, NullTreatment, RexType

from typing_extensions import deprecated

from ._internal import expr as expr_internal

from ._internal import functions as functions_internal

if TYPE_CHECKING:

from datafusion.plan import LogicalPlan

# The following are imported from the internal representation. We may choose to

# give these all proper wrappers, or to simply leave as is. These were added

# in order to support passing the `test_imports` unit test.

# Tim Saucer note: It is not clear to me what the use case is for exposing

# these definitions to the end user.

Alias = expr_internal.Alias

Analyze = expr_internal.Analyze

Aggregate = expr_internal.Aggregate

AggregateFunction = expr_internal.AggregateFunction

Between = expr_internal.Between

BinaryExpr = expr_internal.BinaryExpr

Case = expr_internal.Case

Cast = expr_internal.Cast

Column = expr_internal.Column

CreateMemoryTable = expr_internal.CreateMemoryTable

CreateView = expr_internal.CreateView

Distinct = expr_internal.Distinct

DropTable = expr_internal.DropTable

EmptyRelation = expr_internal.EmptyRelation

Exists = expr_internal.Exists

Explain = expr_internal.Explain

Extension = expr_internal.Extension

Filter = expr_internal.Filter

GroupingSet = expr_internal.GroupingSet

Join = expr_internal.Join

ILike = expr_internal.ILike

InList = expr_internal.InList

InSubquery = expr_internal.InSubquery

IsFalse = expr_internal.IsFalse

IsNotTrue = expr_internal.IsNotTrue

IsNull = expr_internal.IsNull

IsTrue = expr_internal.IsTrue

IsUnknown = expr_internal.IsUnknown

IsNotFalse = expr_internal.IsNotFalse

IsNotNull = expr_internal.IsNotNull

IsNotUnknown = expr_internal.IsNotUnknown

JoinConstraint = expr_internal.JoinConstraint

JoinType = expr_internal.JoinType

Like = expr_internal.Like

Limit = expr_internal.Limit

Literal = expr_internal.Literal

Negative = expr_internal.Negative

Not = expr_internal.Not

Partitioning = expr_internal.Partitioning

Placeholder = expr_internal.Placeholder

Projection = expr_internal.Projection

Repartition = expr_internal.Repartition

ScalarSubquery = expr_internal.ScalarSubquery

ScalarVariable = expr_internal.ScalarVariable

SimilarTo = expr_internal.SimilarTo

Sort = expr_internal.Sort

Subquery = expr_internal.Subquery

SubqueryAlias = expr_internal.SubqueryAlias

TableScan = expr_internal.TableScan

TryCast = expr_internal.TryCast

Union = expr_internal.Union

Unnest = expr_internal.Unnest

UnnestExpr = expr_internal.UnnestExpr

WindowExpr = expr_internal.WindowExpr

__all__ = [

"Expr",

"Column",

"Literal",

"BinaryExpr",

"Literal",

"AggregateFunction",

"Not",

"IsNotNull",

"IsNull",

"IsTrue",

"IsFalse",

"IsUnknown",

"IsNotTrue",

"IsNotFalse",

"IsNotUnknown",

"Negative",

"Like",

"ILike",

"SimilarTo",

"ScalarVariable",

"Alias",

"InList",

"Exists",

"Subquery",

"InSubquery",

"ScalarSubquery",

"Placeholder",

"GroupingSet",

"Case",

"CaseBuilder",

"Cast",

"TryCast",

"Between",

"Explain",

"Limit",

"Aggregate",

"Sort",

"SortExpr",

"Analyze",

"EmptyRelation",

"Join",

"JoinType",

"JoinConstraint",

"Union",

"Unnest",

"UnnestExpr",

"Extension",

"Filter",

"Projection",

"TableScan",

"CreateMemoryTable",

"CreateView",

"Distinct",

"SubqueryAlias",

"DropTable",

"Partitioning",

"Repartition",

"Window",

"WindowExpr",

"WindowFrame",

"WindowFrameBound",

]

def expr_list_to_raw_expr_list(

expr_list: Optional[list[Expr]],

) -> Optional[list[expr_internal.Expr]]:

"""Helper function to convert an optional list to raw expressions."""

return [e.expr for e in expr_list] if expr_list is not None else None

def sort_or_default(e: Expr | SortExpr) -> expr_internal.SortExpr:

"""Helper function to return a default Sort if an Expr is provided."""

if isinstance(e, SortExpr):

return e.raw_sort

return SortExpr(e.expr, True, True).raw_sort

def sort_list_to_raw_sort_list(

sort_list: Optional[list[Expr | SortExpr]],

) -> Optional[list[expr_internal.SortExpr]]:

"""Helper function to return an optional sort list to raw variant."""

return [sort_or_default(e) for e in sort_list] if sort_list is not None else None

class Expr:

"""Expression object.

Expressions are one of the core concepts in DataFusion. See

:ref:`Expressions` in the online documentation for more information.

"""

def __init__(self, expr: expr_internal.Expr) -> None:

"""This constructor should not be called by the end user."""

self.expr = expr

def to_variant(self) -> Any:

"""Convert this expression into a python object if possible."""

return self.expr.to_variant()

@deprecated(

"display_name() is deprecated. Use :py:meth:`~Expr.schema_name` instead"

)

def display_name(self) -> str:

"""Returns the name of this expression as it should appear in a schema.

This name will not include any CAST expressions.

"""

return self.schema_name()

def schema_name(self) -> str:

"""Returns the name of this expression as it should appear in a schema.

This name will not include any CAST expressions.

"""

return self.expr.schema_name()

def canonical_name(self) -> str:

"""Returns a complete string representation of this expression."""

return self.expr.canonical_name()

def variant_name(self) -> str:

"""Returns the name of the Expr variant.

Ex: ``IsNotNull``, ``Literal``, ``BinaryExpr``, etc

"""

return self.expr.variant_name()

def __richcmp__(self, other: Expr, op: int) -> Expr:

"""Comparison operator."""

return Expr(self.expr.__richcmp__(other, op))

def __repr__(self) -> str:

"""Generate a string representation of this expression."""

return self.expr.__repr__()

def __add__(self, rhs: Any) -> Expr:

"""Addition operator.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__add__(rhs.expr))

def __sub__(self, rhs: Any) -> Expr:

"""Subtraction operator.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__sub__(rhs.expr))

def __truediv__(self, rhs: Any) -> Expr:

"""Division operator.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__truediv__(rhs.expr))

def __mul__(self, rhs: Any) -> Expr:

"""Multiplication operator.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__mul__(rhs.expr))

def __mod__(self, rhs: Any) -> Expr:

"""Modulo operator (%).

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__mod__(rhs.expr))

def __and__(self, rhs: Expr) -> Expr:

"""Logical AND."""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__and__(rhs.expr))

def __or__(self, rhs: Expr) -> Expr:

"""Logical OR."""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__or__(rhs.expr))

def __invert__(self) -> Expr:

"""Binary not (~)."""

return Expr(self.expr.__invert__())

def __getitem__(self, key: str | int) -> Expr:

"""Retrieve sub-object.

If ``key`` is a string, returns the subfield of the struct.

If ``key`` is an integer, retrieves the element in the array. Note that the

element index begins at ``0``, unlike `array_element` which begins at ``1``.

"""

if isinstance(key, int):

return Expr(

functions_internal.array_element(self.expr, Expr.literal(key + 1).expr)

)

return Expr(self.expr.__getitem__(key))

def __eq__(self, rhs: Any) -> Expr:

"""Equal to.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__eq__(rhs.expr))

def __ne__(self, rhs: Any) -> Expr:

"""Not equal to.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__ne__(rhs.expr))

def __ge__(self, rhs: Any) -> Expr:

"""Greater than or equal to.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__ge__(rhs.expr))

def __gt__(self, rhs: Any) -> Expr:

"""Greater than.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__gt__(rhs.expr))

def __le__(self, rhs: Any) -> Expr:

"""Less than or equal to.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__le__(rhs.expr))

def __lt__(self, rhs: Any) -> Expr:

"""Less than.

Accepts either an expression or any valid PyArrow scalar literal value.

"""

if not isinstance(rhs, Expr):

rhs = Expr.literal(rhs)

return Expr(self.expr.__lt__(rhs.expr))

__radd__ = __add__

__rand__ = __and__

__rmod__ = __mod__

__rmul__ = __mul__

__ror__ = __or__

__rsub__ = __sub__

__rtruediv__ = __truediv__

@staticmethod

def literal(value: Any) -> Expr:

"""Creates a new expression representing a scalar value.

``value`` must be a valid PyArrow scalar value or easily castable to one.

"""

if isinstance(value, str):

value = pa.scalar(value, type=pa.string_view())

if not isinstance(value, pa.Scalar):

value = pa.scalar(value)

return Expr(expr_internal.Expr.literal(value))

@staticmethod

def column(value: str) -> Expr:

"""Creates a new expression representing a column."""

return Expr(expr_internal.Expr.column(value))

def alias(self, name: str) -> Expr:

"""Assign a name to the expression."""

return Expr(self.expr.alias(name))

def sort(self, ascending: bool = True, nulls_first: bool = True) -> SortExpr:

"""Creates a sort :py:class:`Expr` from an existing :py:class:`Expr`.

Args:

ascending: If true, sort in ascending order.

nulls_first: Return null values first.

"""

return SortExpr(self.expr, ascending=ascending, nulls_first=nulls_first)

def is_null(self) -> Expr:

"""Returns ``True`` if this expression is null."""

return Expr(self.expr.is_null())

def is_not_null(self) -> Expr:

"""Returns ``True`` if this expression is not null."""

return Expr(self.expr.is_not_null())

def fill_nan(self, value: Any | Expr | None = None) -> Expr:

"""Fill NaN values with a provided value."""

if not isinstance(value, Expr):

value = Expr.literal(value)

return Expr(functions_internal.nanvl(self.expr, value.expr))

def fill_null(self, value: Any | Expr | None = None) -> Expr:

"""Fill NULL values with a provided value."""

if not isinstance(value, Expr):

value = Expr.literal(value)

return Expr(functions_internal.nvl(self.expr, value.expr))

_to_pyarrow_types = {

float: pa.float64(),

int: pa.int64(),

str: pa.string(),

bool: pa.bool_(),

}

def cast(

self, to: pa.DataType[Any] | Type[float] | Type[int] | Type[str] | Type[bool]

) -> Expr:

"""Cast to a new data type."""

if not isinstance(to, pa.DataType):

try:

to = self._to_pyarrow_types[to]

except KeyError:

raise TypeError(

"Expected instance of pyarrow.DataType or builtins.type"

)

return Expr(self.expr.cast(to))

def between(self, low: Any, high: Any, negated: bool = False) -> Expr:

"""Returns ``True`` if this expression is between a given range.

Args:

low: lower bound of the range (inclusive).

high: higher bound of the range (inclusive).

negated: negates whether the expression is between a given range

"""

if not isinstance(low, Expr):

low = Expr.literal(low)

if not isinstance(high, Expr):

high = Expr.literal(high)

return Expr(self.expr.between(low.expr, high.expr, negated=negated))

def rex_type(self) -> RexType:

"""Return the Rex Type of this expression.

A Rex (Row Expression) specifies a single row of data.That specification

could include user defined functions or types. RexType identifies the

row as one of the possible valid ``RexType``.

"""

return self.expr.rex_type()

def types(self) -> DataTypeMap:

"""Return the ``DataTypeMap``.

Returns:

DataTypeMap which represents the PythonType, Arrow DataType, and

SqlType Enum which this expression represents.

"""

return self.expr.types()

def python_value(self) -> Any:

"""Extracts the Expr value into a PyObject.

This is only valid for literal expressions.

Returns:

Python object representing literal value of the expression.

"""

return self.expr.python_value()

def rex_call_operands(self) -> list[Expr]:

"""Return the operands of the expression based on it's variant type.

Row expressions, Rex(s), operate on the concept of operands. Different

variants of Expressions, Expr(s), store those operands in different

datastructures. This function examines the Expr variant and returns

the operands to the calling logic.

"""

return [Expr(e) for e in self.expr.rex_call_operands()]

def rex_call_operator(self) -> str:

"""Extracts the operator associated with a row expression type call."""

return self.expr.rex_call_operator()

def column_name(self, plan: LogicalPlan) -> str:

"""Compute the output column name based on the provided logical plan."""

return self.expr.column_name(plan._raw_plan)

def order_by(self, *exprs: Expr | SortExpr) -> ExprFuncBuilder:

"""Set the ordering for a window or aggregate function.

This function will create an :py:class:`ExprFuncBuilder` that can be used to

set parameters for either window or aggregate functions. If used on any other

type of expression, an error will be generated when ``build()`` is called.

"""

return ExprFuncBuilder(self.expr.order_by([sort_or_default(e) for e in exprs]))

def filter(self, filter: Expr) -> ExprFuncBuilder:

"""Filter an aggregate function.

This function will create an :py:class:`ExprFuncBuilder` that can be used to

set parameters for either window or aggregate functions. If used on any other

type of expression, an error will be generated when ``build()`` is called.

"""

return ExprFuncBuilder(self.expr.filter(filter.expr))

def distinct(self) -> ExprFuncBuilder:

"""Only evaluate distinct values for an aggregate function.

This function will create an :py:class:`ExprFuncBuilder` that can be used to

set parameters for either window or aggregate functions. If used on any other

type of expression, an error will be generated when ``build()`` is called.

"""

return ExprFuncBuilder(self.expr.distinct())

def null_treatment(self, null_treatment: NullTreatment) -> ExprFuncBuilder:

"""Set the treatment for ``null`` values for a window or aggregate function.

This function will create an :py:class:`ExprFuncBuilder` that can be used to

set parameters for either window or aggregate functions. If used on any other

type of expression, an error will be generated when ``build()`` is called.

"""

return ExprFuncBuilder(self.expr.null_treatment(null_treatment.value))

def partition_by(self, *partition_by: Expr) -> ExprFuncBuilder:

"""Set the partitioning for a window function.

This function will create an :py:class:`ExprFuncBuilder` that can be used to

set parameters for either window or aggregate functions. If used on any other

type of expression, an error will be generated when ``build()`` is called.

"""

return ExprFuncBuilder(

self.expr.partition_by(list(e.expr for e in partition_by))

)

def window_frame(self, window_frame: WindowFrame) -> ExprFuncBuilder:

"""Set the frame fora window function.

This function will create an :py:class:`ExprFuncBuilder` that can be used to

set parameters for either window or aggregate functions. If used on any other

type of expression, an error will be generated when ``build()`` is called.

"""

return ExprFuncBuilder(self.expr.window_frame(window_frame.window_frame))

def over(self, window: Window) -> Expr:

"""Turn an aggregate function into a window function.

This function turns any aggregate function into a window function. With the

exception of ``partition_by``, how each of the parameters is used is determined

by the underlying aggregate function.

Args:

window: Window definition

"""

partition_by_raw = expr_list_to_raw_expr_list(window._partition_by)

order_by_raw = sort_list_to_raw_sort_list(window._order_by)

window_frame_raw = (

window._window_frame.window_frame

if window._window_frame is not None

else None

)

null_treatment_raw = (

window._null_treatment.value if window._null_treatment is not None else None

)

return Expr(

self.expr.over(

partition_by=partition_by_raw,

order_by=order_by_raw,

window_frame=window_frame_raw,

null_treatment=null_treatment_raw,

)

class ExprFuncBuilder:

def __init__(self, builder: expr_internal.ExprFuncBuilder):

self.builder = builder

def order_by(self, *exprs: Expr) -> ExprFuncBuilder:

"""Set the ordering for a window or aggregate function.

Values given in ``exprs`` must be sort expressions. You can convert any other

expression to a sort expression using `.sort()`.

"""

return ExprFuncBuilder(

self.builder.order_by([sort_or_default(e) for e in exprs])

)

def filter(self, filter: Expr) -> ExprFuncBuilder:

"""Filter values during aggregation."""

return ExprFuncBuilder(self.builder.filter(filter.expr))

def distinct(self) -> ExprFuncBuilder:

"""Only evaluate distinct values during aggregation."""

return ExprFuncBuilder(self.builder.distinct())

def null_treatment(self, null_treatment: NullTreatment) -> ExprFuncBuilder:

"""Set how nulls are treated for either window or aggregate functions."""

return ExprFuncBuilder(self.builder.null_treatment(null_treatment.value))

def partition_by(self, *partition_by: Expr) -> ExprFuncBuilder:

"""Set partitioning for window functions."""

return ExprFuncBuilder(

self.builder.partition_by(list(e.expr for e in partition_by))

)

def window_frame(self, window_frame: WindowFrame) -> ExprFuncBuilder:

"""Set window frame for window functions."""

return ExprFuncBuilder(self.builder.window_frame(window_frame.window_frame))

def build(self) -> Expr:

"""Create an expression from a Function Builder."""

return Expr(self.builder.build())

class Window:

"""Define reusable window parameters."""

def __init__(

self,

partition_by: Optional[list[Expr]] = None,

window_frame: Optional[WindowFrame] = None,

order_by: Optional[list[SortExpr | Expr]] = None,

null_treatment: Optional[NullTreatment] = None,

) -> None:

"""Construct a window definition.

Args:

partition_by: Partitions for window operation

window_frame: Define the start and end bounds of the window frame

order_by: Set ordering

null_treatment: Indicate how nulls are to be treated

"""

self._partition_by = partition_by

self._window_frame = window_frame

self._order_by = order_by

self._null_treatment = null_treatment

class WindowFrame:

"""Defines a window frame for performing window operations."""

def __init__(

self, units: str, start_bound: Optional[Any], end_bound: Optional[Any]

) -> None:

"""Construct a window frame using the given parameters.

Args:

units: Should be one of ``rows``, ``range``, or ``groups``.

start_bound: Sets the preceding bound. Must be >= 0. If none, this

will be set to unbounded. If unit type is ``groups``, this

parameter must be set.

end_bound: Sets the following bound. Must be >= 0. If none, this

will be set to unbounded. If unit type is ``groups``, this

parameter must be set.

"""

if not isinstance(start_bound, pa.Scalar) and start_bound is not None:

start_bound = pa.scalar(start_bound)

if units == "rows" or units == "groups":

start_bound = start_bound.cast(pa.uint64())

if not isinstance(end_bound, pa.Scalar) and end_bound is not None:

end_bound = pa.scalar(end_bound)

if units == "rows" or units == "groups":

end_bound = end_bound.cast(pa.uint64())

self.window_frame = expr_internal.WindowFrame(units, start_bound, end_bound)

def get_frame_units(self) -> str:

"""Returns the window frame units for the bounds."""

return self.window_frame.get_frame_units()

def get_lower_bound(self) -> WindowFrameBound:

"""Returns starting bound."""

return WindowFrameBound(self.window_frame.get_lower_bound())

def get_upper_bound(self):

"""Returns end bound."""

return WindowFrameBound(self.window_frame.get_upper_bound())

class WindowFrameBound:

"""Defines a single window frame bound.

:py:class:`WindowFrame` typically requires a start and end bound.

"""

def __init__(self, frame_bound: expr_internal.WindowFrameBound) -> None:

"""Constructs a window frame bound."""

self.frame_bound = frame_bound

def get_offset(self) -> int | None:

"""Returns the offset of the window frame."""

return self.frame_bound.get_offset()

def is_current_row(self) -> bool:

"""Returns if the frame bound is current row."""

return self.frame_bound.is_current_row()

def is_following(self) -> bool:

"""Returns if the frame bound is following."""

return self.frame_bound.is_following()

def is_preceding(self) -> bool:

"""Returns if the frame bound is preceding."""

return self.frame_bound.is_preceding()

def is_unbounded(self) -> bool:

"""Returns if the frame bound is unbounded."""

return self.frame_bound.is_unbounded()

class CaseBuilder:

"""Builder class for constructing case statements.

An example usage would be as follows::

import datafusion.functions as f

from datafusion import lit, col

df.select(

f.case(col("column_a")

.when(lit(1), lit("One"))

.when(lit(2), lit("Two"))

.otherwise(lit("Unknown"))

)

"""

def __init__(self, case_builder: expr_internal.CaseBuilder) -> None:

"""Constructs a case builder.

This is not typically called by the end user directly. See

:py:func:`datafusion.functions.case` instead.

"""

self.case_builder = case_builder

def when(self, when_expr: Expr, then_expr: Expr) -> CaseBuilder:

"""Add a case to match against."""

return CaseBuilder(self.case_builder.when(when_expr.expr, then_expr.expr))

def otherwise(self, else_expr: Expr) -> Expr:

"""Set a default value for the case statement."""

return Expr(self.case_builder.otherwise(else_expr.expr))

def end(self) -> Expr:

"""Finish building a case statement.

Any non-matching cases will end in a `null` value.

"""

return Expr(self.case_builder.end())

class SortExpr:

"""Used to specify sorting on either a DataFrame or function."""

def __init__(self, expr: Expr, ascending: bool, nulls_first: bool) -> None:

"""This constructor should not be called by the end user."""

self.raw_sort = expr_internal.SortExpr(expr, ascending, nulls_first)

def expr(self) -> Expr:

"""Return the raw expr backing the SortExpr."""

return Expr(self.raw_sort.expr())

def ascending(self) -> bool:

"""Return ascending property."""

return self.raw_sort.ascending()

def nulls_first(self) -> bool:

"""Return nulls_first property."""

return self.raw_sort.nulls_first()

def __repr__(self) -> str:

"""Generate a string representation of this expression."""

return self.raw_sort.__repr__()

datafusion-python/python/datafusion/expr.py at main · ongchi/datafusion-python · GitHub

Expand file tree

Breadcrumbs

expr.py

Latest commit

History

Breadcrumbs

expr.py

File metadata and controls