sqlglot.optimizer.simplify
1import datetime 2import functools 3import itertools 4import typing as t 5from collections import deque 6from decimal import Decimal 7 8import sqlglot 9from sqlglot import exp 10from sqlglot.helper import first, is_iterable, merge_ranges, while_changing 11from sqlglot.optimizer.scope import find_all_in_scope, walk_in_scope 12 13# Final means that an expression should not be simplified 14FINAL = "final" 15 16 17class UnsupportedUnit(Exception): 18 pass 19 20 21def simplify(expression, constant_propagation=False): 22 """ 23 Rewrite sqlglot AST to simplify expressions. 24 25 Example: 26 >>> import sqlglot 27 >>> expression = sqlglot.parse_one("TRUE AND TRUE") 28 >>> simplify(expression).sql() 29 'TRUE' 30 31 Args: 32 expression (sqlglot.Expression): expression to simplify 33 constant_propagation: whether or not the constant propagation rule should be used 34 35 Returns: 36 sqlglot.Expression: simplified expression 37 """ 38 39 # group by expressions cannot be simplified, for example 40 # select x + 1 + 1 FROM y GROUP BY x + 1 + 1 41 # the projection must exactly match the group by key 42 for group in expression.find_all(exp.Group): 43 select = group.parent 44 groups = set(group.expressions) 45 group.meta[FINAL] = True 46 47 for e in select.selects: 48 for node, *_ in e.walk(): 49 if node in groups: 50 e.meta[FINAL] = True 51 break 52 53 having = select.args.get("having") 54 if having: 55 for node, *_ in having.walk(): 56 if node in groups: 57 having.meta[FINAL] = True 58 break 59 60 def _simplify(expression, root=True): 61 if expression.meta.get(FINAL): 62 return expression 63 64 # Pre-order transformations 65 node = expression 66 node = rewrite_between(node) 67 node = uniq_sort(node, root) 68 node = absorb_and_eliminate(node, root) 69 node = simplify_concat(node) 70 node = simplify_conditionals(node) 71 72 if constant_propagation: 73 node = propagate_constants(node, root) 74 75 exp.replace_children(node, lambda e: _simplify(e, False)) 76 77 # Post-order transformations 78 node = simplify_not(node) 79 node = flatten(node) 80 node = simplify_connectors(node, root) 81 node = remove_complements(node, root) 82 node = simplify_coalesce(node) 83 node.parent = expression.parent 84 node = simplify_literals(node, root) 85 node = simplify_equality(node) 86 node = simplify_parens(node) 87 node = simplify_datetrunc_predicate(node) 88 89 if root: 90 expression.replace(node) 91 92 return node 93 94 expression = while_changing(expression, _simplify) 95 remove_where_true(expression) 96 return expression 97 98 99def catch(*exceptions): 100 """Decorator that ignores a simplification function if any of `exceptions` are raised""" 101 102 def decorator(func): 103 def wrapped(expression, *args, **kwargs): 104 try: 105 return func(expression, *args, **kwargs) 106 except exceptions: 107 return expression 108 109 return wrapped 110 111 return decorator 112 113 114def rewrite_between(expression: exp.Expression) -> exp.Expression: 115 """Rewrite x between y and z to x >= y AND x <= z. 116 117 This is done because comparison simplification is only done on lt/lte/gt/gte. 118 """ 119 if isinstance(expression, exp.Between): 120 return exp.and_( 121 exp.GTE(this=expression.this.copy(), expression=expression.args["low"]), 122 exp.LTE(this=expression.this.copy(), expression=expression.args["high"]), 123 copy=False, 124 ) 125 return expression 126 127 128def simplify_not(expression): 129 """ 130 Demorgan's Law 131 NOT (x OR y) -> NOT x AND NOT y 132 NOT (x AND y) -> NOT x OR NOT y 133 """ 134 if isinstance(expression, exp.Not): 135 if is_null(expression.this): 136 return exp.null() 137 if isinstance(expression.this, exp.Paren): 138 condition = expression.this.unnest() 139 if isinstance(condition, exp.And): 140 return exp.or_( 141 exp.not_(condition.left, copy=False), 142 exp.not_(condition.right, copy=False), 143 copy=False, 144 ) 145 if isinstance(condition, exp.Or): 146 return exp.and_( 147 exp.not_(condition.left, copy=False), 148 exp.not_(condition.right, copy=False), 149 copy=False, 150 ) 151 if is_null(condition): 152 return exp.null() 153 if always_true(expression.this): 154 return exp.false() 155 if is_false(expression.this): 156 return exp.true() 157 if isinstance(expression.this, exp.Not): 158 # double negation 159 # NOT NOT x -> x 160 return expression.this.this 161 return expression 162 163 164def flatten(expression): 165 """ 166 A AND (B AND C) -> A AND B AND C 167 A OR (B OR C) -> A OR B OR C 168 """ 169 if isinstance(expression, exp.Connector): 170 for node in expression.args.values(): 171 child = node.unnest() 172 if isinstance(child, expression.__class__): 173 node.replace(child) 174 return expression 175 176 177def simplify_connectors(expression, root=True): 178 def _simplify_connectors(expression, left, right): 179 if left == right: 180 return left 181 if isinstance(expression, exp.And): 182 if is_false(left) or is_false(right): 183 return exp.false() 184 if is_null(left) or is_null(right): 185 return exp.null() 186 if always_true(left) and always_true(right): 187 return exp.true() 188 if always_true(left): 189 return right 190 if always_true(right): 191 return left 192 return _simplify_comparison(expression, left, right) 193 elif isinstance(expression, exp.Or): 194 if always_true(left) or always_true(right): 195 return exp.true() 196 if is_false(left) and is_false(right): 197 return exp.false() 198 if ( 199 (is_null(left) and is_null(right)) 200 or (is_null(left) and is_false(right)) 201 or (is_false(left) and is_null(right)) 202 ): 203 return exp.null() 204 if is_false(left): 205 return right 206 if is_false(right): 207 return left 208 return _simplify_comparison(expression, left, right, or_=True) 209 210 if isinstance(expression, exp.Connector): 211 return _flat_simplify(expression, _simplify_connectors, root) 212 return expression 213 214 215LT_LTE = (exp.LT, exp.LTE) 216GT_GTE = (exp.GT, exp.GTE) 217 218COMPARISONS = ( 219 *LT_LTE, 220 *GT_GTE, 221 exp.EQ, 222 exp.NEQ, 223 exp.Is, 224) 225 226INVERSE_COMPARISONS: t.Dict[t.Type[exp.Expression], t.Type[exp.Expression]] = { 227 exp.LT: exp.GT, 228 exp.GT: exp.LT, 229 exp.LTE: exp.GTE, 230 exp.GTE: exp.LTE, 231} 232 233 234def _simplify_comparison(expression, left, right, or_=False): 235 if isinstance(left, COMPARISONS) and isinstance(right, COMPARISONS): 236 ll, lr = left.args.values() 237 rl, rr = right.args.values() 238 239 largs = {ll, lr} 240 rargs = {rl, rr} 241 242 matching = largs & rargs 243 columns = {m for m in matching if isinstance(m, exp.Column)} 244 245 if matching and columns: 246 try: 247 l = first(largs - columns) 248 r = first(rargs - columns) 249 except StopIteration: 250 return expression 251 252 # make sure the comparison is always of the form x > 1 instead of 1 < x 253 if left.__class__ in INVERSE_COMPARISONS and l == ll: 254 left = INVERSE_COMPARISONS[left.__class__](this=lr, expression=ll) 255 if right.__class__ in INVERSE_COMPARISONS and r == rl: 256 right = INVERSE_COMPARISONS[right.__class__](this=rr, expression=rl) 257 258 if l.is_number and r.is_number: 259 l = float(l.name) 260 r = float(r.name) 261 elif l.is_string and r.is_string: 262 l = l.name 263 r = r.name 264 else: 265 return None 266 267 for (a, av), (b, bv) in itertools.permutations(((left, l), (right, r))): 268 if isinstance(a, LT_LTE) and isinstance(b, LT_LTE): 269 return left if (av > bv if or_ else av <= bv) else right 270 if isinstance(a, GT_GTE) and isinstance(b, GT_GTE): 271 return left if (av < bv if or_ else av >= bv) else right 272 273 # we can't ever shortcut to true because the column could be null 274 if not or_: 275 if isinstance(a, exp.LT) and isinstance(b, GT_GTE): 276 if av <= bv: 277 return exp.false() 278 elif isinstance(a, exp.GT) and isinstance(b, LT_LTE): 279 if av >= bv: 280 return exp.false() 281 elif isinstance(a, exp.EQ): 282 if isinstance(b, exp.LT): 283 return exp.false() if av >= bv else a 284 if isinstance(b, exp.LTE): 285 return exp.false() if av > bv else a 286 if isinstance(b, exp.GT): 287 return exp.false() if av <= bv else a 288 if isinstance(b, exp.GTE): 289 return exp.false() if av < bv else a 290 if isinstance(b, exp.NEQ): 291 return exp.false() if av == bv else a 292 return None 293 294 295def remove_complements(expression, root=True): 296 """ 297 Removing complements. 298 299 A AND NOT A -> FALSE 300 A OR NOT A -> TRUE 301 """ 302 if isinstance(expression, exp.Connector) and (root or not expression.same_parent): 303 complement = exp.false() if isinstance(expression, exp.And) else exp.true() 304 305 for a, b in itertools.permutations(expression.flatten(), 2): 306 if is_complement(a, b): 307 return complement 308 return expression 309 310 311def uniq_sort(expression, root=True): 312 """ 313 Uniq and sort a connector. 314 315 C AND A AND B AND B -> A AND B AND C 316 """ 317 if isinstance(expression, exp.Connector) and (root or not expression.same_parent): 318 result_func = exp.and_ if isinstance(expression, exp.And) else exp.or_ 319 flattened = tuple(expression.flatten()) 320 deduped = {gen(e): e for e in flattened} 321 arr = tuple(deduped.items()) 322 323 # check if the operands are already sorted, if not sort them 324 # A AND C AND B -> A AND B AND C 325 for i, (sql, e) in enumerate(arr[1:]): 326 if sql < arr[i][0]: 327 expression = result_func(*(e for _, e in sorted(arr)), copy=False) 328 break 329 else: 330 # we didn't have to sort but maybe we need to dedup 331 if len(deduped) < len(flattened): 332 expression = result_func(*deduped.values(), copy=False) 333 334 return expression 335 336 337def absorb_and_eliminate(expression, root=True): 338 """ 339 absorption: 340 A AND (A OR B) -> A 341 A OR (A AND B) -> A 342 A AND (NOT A OR B) -> A AND B 343 A OR (NOT A AND B) -> A OR B 344 elimination: 345 (A AND B) OR (A AND NOT B) -> A 346 (A OR B) AND (A OR NOT B) -> A 347 """ 348 if isinstance(expression, exp.Connector) and (root or not expression.same_parent): 349 kind = exp.Or if isinstance(expression, exp.And) else exp.And 350 351 for a, b in itertools.permutations(expression.flatten(), 2): 352 if isinstance(a, kind): 353 aa, ab = a.unnest_operands() 354 355 # absorb 356 if is_complement(b, aa): 357 aa.replace(exp.true() if kind == exp.And else exp.false()) 358 elif is_complement(b, ab): 359 ab.replace(exp.true() if kind == exp.And else exp.false()) 360 elif (set(b.flatten()) if isinstance(b, kind) else {b}) < set(a.flatten()): 361 a.replace(exp.false() if kind == exp.And else exp.true()) 362 elif isinstance(b, kind): 363 # eliminate 364 rhs = b.unnest_operands() 365 ba, bb = rhs 366 367 if aa in rhs and (is_complement(ab, ba) or is_complement(ab, bb)): 368 a.replace(aa) 369 b.replace(aa) 370 elif ab in rhs and (is_complement(aa, ba) or is_complement(aa, bb)): 371 a.replace(ab) 372 b.replace(ab) 373 374 return expression 375 376 377def propagate_constants(expression, root=True): 378 """ 379 Propagate constants for conjunctions in DNF: 380 381 SELECT * FROM t WHERE a = b AND b = 5 becomes 382 SELECT * FROM t WHERE a = 5 AND b = 5 383 384 Reference: https://www.sqlite.org/optoverview.html 385 """ 386 387 if ( 388 isinstance(expression, exp.And) 389 and (root or not expression.same_parent) 390 and sqlglot.optimizer.normalize.normalized(expression, dnf=True) 391 ): 392 constant_mapping = {} 393 for expr, *_ in walk_in_scope(expression, prune=lambda node, *_: isinstance(node, exp.If)): 394 if isinstance(expr, exp.EQ): 395 l, r = expr.left, expr.right 396 397 # TODO: create a helper that can be used to detect nested literal expressions such 398 # as CAST(123456 AS BIGINT), since we usually want to treat those as literals too 399 if isinstance(l, exp.Column) and isinstance(r, exp.Literal): 400 pass 401 elif isinstance(r, exp.Column) and isinstance(l, exp.Literal): 402 l, r = r, l 403 else: 404 continue 405 406 constant_mapping[l] = (id(l), r) 407 408 if constant_mapping: 409 for column in find_all_in_scope(expression, exp.Column): 410 parent = column.parent 411 column_id, constant = constant_mapping.get(column) or (None, None) 412 if ( 413 column_id is not None 414 and id(column) != column_id 415 and not (isinstance(parent, exp.Is) and isinstance(parent.expression, exp.Null)) 416 ): 417 column.replace(constant.copy()) 418 419 return expression 420 421 422INVERSE_DATE_OPS: t.Dict[t.Type[exp.Expression], t.Type[exp.Expression]] = { 423 exp.DateAdd: exp.Sub, 424 exp.DateSub: exp.Add, 425 exp.DatetimeAdd: exp.Sub, 426 exp.DatetimeSub: exp.Add, 427} 428 429INVERSE_OPS: t.Dict[t.Type[exp.Expression], t.Type[exp.Expression]] = { 430 **INVERSE_DATE_OPS, 431 exp.Add: exp.Sub, 432 exp.Sub: exp.Add, 433} 434 435 436def _is_number(expression: exp.Expression) -> bool: 437 return expression.is_number 438 439 440def _is_interval(expression: exp.Expression) -> bool: 441 return isinstance(expression, exp.Interval) and extract_interval(expression) is not None 442 443 444@catch(ModuleNotFoundError, UnsupportedUnit) 445def simplify_equality(expression: exp.Expression) -> exp.Expression: 446 """ 447 Use the subtraction and addition properties of equality to simplify expressions: 448 449 x + 1 = 3 becomes x = 2 450 451 There are two binary operations in the above expression: + and = 452 Here's how we reference all the operands in the code below: 453 454 l r 455 x + 1 = 3 456 a b 457 """ 458 if isinstance(expression, COMPARISONS): 459 l, r = expression.left, expression.right 460 461 if l.__class__ in INVERSE_OPS: 462 pass 463 elif r.__class__ in INVERSE_OPS: 464 l, r = r, l 465 else: 466 return expression 467 468 if r.is_number: 469 a_predicate = _is_number 470 b_predicate = _is_number 471 elif _is_date_literal(r): 472 a_predicate = _is_date_literal 473 b_predicate = _is_interval 474 else: 475 return expression 476 477 if l.__class__ in INVERSE_DATE_OPS: 478 l = t.cast(exp.IntervalOp, l) 479 a = l.this 480 b = l.interval() 481 else: 482 l = t.cast(exp.Binary, l) 483 a, b = l.left, l.right 484 485 if not a_predicate(a) and b_predicate(b): 486 pass 487 elif not a_predicate(b) and b_predicate(a): 488 a, b = b, a 489 else: 490 return expression 491 492 return expression.__class__( 493 this=a, expression=INVERSE_OPS[l.__class__](this=r, expression=b) 494 ) 495 return expression 496 497 498def simplify_literals(expression, root=True): 499 if isinstance(expression, exp.Binary) and not isinstance(expression, exp.Connector): 500 return _flat_simplify(expression, _simplify_binary, root) 501 502 if isinstance(expression, exp.Neg): 503 this = expression.this 504 if this.is_number: 505 value = this.name 506 if value[0] == "-": 507 return exp.Literal.number(value[1:]) 508 return exp.Literal.number(f"-{value}") 509 510 return expression 511 512 513def _simplify_binary(expression, a, b): 514 if isinstance(expression, exp.Is): 515 if isinstance(b, exp.Not): 516 c = b.this 517 not_ = True 518 else: 519 c = b 520 not_ = False 521 522 if is_null(c): 523 if isinstance(a, exp.Literal): 524 return exp.true() if not_ else exp.false() 525 if is_null(a): 526 return exp.false() if not_ else exp.true() 527 elif isinstance(expression, (exp.NullSafeEQ, exp.NullSafeNEQ)): 528 return None 529 elif is_null(a) or is_null(b): 530 return exp.null() 531 532 if a.is_number and b.is_number: 533 a = int(a.name) if a.is_int else Decimal(a.name) 534 b = int(b.name) if b.is_int else Decimal(b.name) 535 536 if isinstance(expression, exp.Add): 537 return exp.Literal.number(a + b) 538 if isinstance(expression, exp.Sub): 539 return exp.Literal.number(a - b) 540 if isinstance(expression, exp.Mul): 541 return exp.Literal.number(a * b) 542 if isinstance(expression, exp.Div): 543 # engines have differing int div behavior so intdiv is not safe 544 if isinstance(a, int) and isinstance(b, int): 545 return None 546 return exp.Literal.number(a / b) 547 548 boolean = eval_boolean(expression, a, b) 549 550 if boolean: 551 return boolean 552 elif a.is_string and b.is_string: 553 boolean = eval_boolean(expression, a.this, b.this) 554 555 if boolean: 556 return boolean 557 elif _is_date_literal(a) and isinstance(b, exp.Interval): 558 a, b = extract_date(a), extract_interval(b) 559 if a and b: 560 if isinstance(expression, exp.Add): 561 return date_literal(a + b) 562 if isinstance(expression, exp.Sub): 563 return date_literal(a - b) 564 elif isinstance(a, exp.Interval) and _is_date_literal(b): 565 a, b = extract_interval(a), extract_date(b) 566 # you cannot subtract a date from an interval 567 if a and b and isinstance(expression, exp.Add): 568 return date_literal(a + b) 569 elif _is_date_literal(a) and _is_date_literal(b): 570 if isinstance(expression, exp.Predicate): 571 a, b = extract_date(a), extract_date(b) 572 boolean = eval_boolean(expression, a, b) 573 if boolean: 574 return boolean 575 576 return None 577 578 579def simplify_parens(expression): 580 if not isinstance(expression, exp.Paren): 581 return expression 582 583 this = expression.this 584 parent = expression.parent 585 586 if not isinstance(this, exp.Select) and ( 587 not isinstance(parent, (exp.Condition, exp.Binary)) 588 or isinstance(parent, exp.Paren) 589 or not isinstance(this, exp.Binary) 590 or (isinstance(this, exp.Predicate) and not isinstance(parent, exp.Predicate)) 591 or (isinstance(this, exp.Add) and isinstance(parent, exp.Add)) 592 or (isinstance(this, exp.Mul) and isinstance(parent, exp.Mul)) 593 or (isinstance(this, exp.Mul) and isinstance(parent, (exp.Add, exp.Sub))) 594 ): 595 return this 596 return expression 597 598 599NONNULL_CONSTANTS = ( 600 exp.Literal, 601 exp.Boolean, 602) 603 604CONSTANTS = ( 605 exp.Literal, 606 exp.Boolean, 607 exp.Null, 608) 609 610 611def _is_nonnull_constant(expression: exp.Expression) -> bool: 612 return isinstance(expression, NONNULL_CONSTANTS) or _is_date_literal(expression) 613 614 615def _is_constant(expression: exp.Expression) -> bool: 616 return isinstance(expression, CONSTANTS) or _is_date_literal(expression) 617 618 619def simplify_coalesce(expression): 620 # COALESCE(x) -> x 621 if ( 622 isinstance(expression, exp.Coalesce) 623 and (not expression.expressions or _is_nonnull_constant(expression.this)) 624 # COALESCE is also used as a Spark partitioning hint 625 and not isinstance(expression.parent, exp.Hint) 626 ): 627 return expression.this 628 629 if not isinstance(expression, COMPARISONS): 630 return expression 631 632 if isinstance(expression.left, exp.Coalesce): 633 coalesce = expression.left 634 other = expression.right 635 elif isinstance(expression.right, exp.Coalesce): 636 coalesce = expression.right 637 other = expression.left 638 else: 639 return expression 640 641 # This transformation is valid for non-constants, 642 # but it really only does anything if they are both constants. 643 if not _is_constant(other): 644 return expression 645 646 # Find the first constant arg 647 for arg_index, arg in enumerate(coalesce.expressions): 648 if _is_constant(other): 649 break 650 else: 651 return expression 652 653 coalesce.set("expressions", coalesce.expressions[:arg_index]) 654 655 # Remove the COALESCE function. This is an optimization, skipping a simplify iteration, 656 # since we already remove COALESCE at the top of this function. 657 coalesce = coalesce if coalesce.expressions else coalesce.this 658 659 # This expression is more complex than when we started, but it will get simplified further 660 return exp.paren( 661 exp.or_( 662 exp.and_( 663 coalesce.is_(exp.null()).not_(copy=False), 664 expression.copy(), 665 copy=False, 666 ), 667 exp.and_( 668 coalesce.is_(exp.null()), 669 type(expression)(this=arg.copy(), expression=other.copy()), 670 copy=False, 671 ), 672 copy=False, 673 ) 674 ) 675 676 677CONCATS = (exp.Concat, exp.DPipe) 678SAFE_CONCATS = (exp.SafeConcat, exp.SafeDPipe) 679 680 681def simplify_concat(expression): 682 """Reduces all groups that contain string literals by concatenating them.""" 683 if not isinstance(expression, CONCATS) or ( 684 # We can't reduce a CONCAT_WS call if we don't statically know the separator 685 isinstance(expression, exp.ConcatWs) 686 and not expression.expressions[0].is_string 687 ): 688 return expression 689 690 if isinstance(expression, exp.ConcatWs): 691 sep_expr, *expressions = expression.expressions 692 sep = sep_expr.name 693 concat_type = exp.ConcatWs 694 else: 695 expressions = expression.expressions 696 sep = "" 697 concat_type = exp.SafeConcat if isinstance(expression, SAFE_CONCATS) else exp.Concat 698 699 new_args = [] 700 for is_string_group, group in itertools.groupby( 701 expressions or expression.flatten(), lambda e: e.is_string 702 ): 703 if is_string_group: 704 new_args.append(exp.Literal.string(sep.join(string.name for string in group))) 705 else: 706 new_args.extend(group) 707 708 if len(new_args) == 1 and new_args[0].is_string: 709 return new_args[0] 710 711 if concat_type is exp.ConcatWs: 712 new_args = [sep_expr] + new_args 713 714 return concat_type(expressions=new_args) 715 716 717def simplify_conditionals(expression): 718 """Simplifies expressions like IF, CASE if their condition is statically known.""" 719 if isinstance(expression, exp.Case): 720 this = expression.this 721 for case in expression.args["ifs"]: 722 cond = case.this 723 if this: 724 # Convert CASE x WHEN matching_value ... to CASE WHEN x = matching_value ... 725 cond = cond.replace(this.pop().eq(cond)) 726 727 if always_true(cond): 728 return case.args["true"] 729 730 if always_false(cond): 731 case.pop() 732 if not expression.args["ifs"]: 733 return expression.args.get("default") or exp.null() 734 elif isinstance(expression, exp.If) and not isinstance(expression.parent, exp.Case): 735 if always_true(expression.this): 736 return expression.args["true"] 737 if always_false(expression.this): 738 return expression.args.get("false") or exp.null() 739 740 return expression 741 742 743DateRange = t.Tuple[datetime.date, datetime.date] 744 745 746def _datetrunc_range(date: datetime.date, unit: str) -> t.Optional[DateRange]: 747 """ 748 Get the date range for a DATE_TRUNC equality comparison: 749 750 Example: 751 _datetrunc_range(date(2021-01-01), 'year') == (date(2021-01-01), date(2022-01-01)) 752 Returns: 753 tuple of [min, max) or None if a value can never be equal to `date` for `unit` 754 """ 755 floor = date_floor(date, unit) 756 757 if date != floor: 758 # This will always be False, except for NULL values. 759 return None 760 761 return floor, floor + interval(unit) 762 763 764def _datetrunc_eq_expression(left: exp.Expression, drange: DateRange) -> exp.Expression: 765 """Get the logical expression for a date range""" 766 return exp.and_( 767 left >= date_literal(drange[0]), 768 left < date_literal(drange[1]), 769 copy=False, 770 ) 771 772 773def _datetrunc_eq( 774 left: exp.Expression, date: datetime.date, unit: str 775) -> t.Optional[exp.Expression]: 776 drange = _datetrunc_range(date, unit) 777 if not drange: 778 return None 779 780 return _datetrunc_eq_expression(left, drange) 781 782 783def _datetrunc_neq( 784 left: exp.Expression, date: datetime.date, unit: str 785) -> t.Optional[exp.Expression]: 786 drange = _datetrunc_range(date, unit) 787 if not drange: 788 return None 789 790 return exp.and_( 791 left < date_literal(drange[0]), 792 left >= date_literal(drange[1]), 793 copy=False, 794 ) 795 796 797DateTruncBinaryTransform = t.Callable[ 798 [exp.Expression, datetime.date, str], t.Optional[exp.Expression] 799] 800DATETRUNC_BINARY_COMPARISONS: t.Dict[t.Type[exp.Expression], DateTruncBinaryTransform] = { 801 exp.LT: lambda l, d, u: l < date_literal(date_floor(d, u)), 802 exp.GT: lambda l, d, u: l >= date_literal(date_floor(d, u) + interval(u)), 803 exp.LTE: lambda l, d, u: l < date_literal(date_floor(d, u) + interval(u)), 804 exp.GTE: lambda l, d, u: l >= date_literal(date_ceil(d, u)), 805 exp.EQ: _datetrunc_eq, 806 exp.NEQ: _datetrunc_neq, 807} 808DATETRUNC_COMPARISONS = {exp.In, *DATETRUNC_BINARY_COMPARISONS} 809 810 811def _is_datetrunc_predicate(left: exp.Expression, right: exp.Expression) -> bool: 812 return isinstance(left, (exp.DateTrunc, exp.TimestampTrunc)) and _is_date_literal(right) 813 814 815@catch(ModuleNotFoundError, UnsupportedUnit) 816def simplify_datetrunc_predicate(expression: exp.Expression) -> exp.Expression: 817 """Simplify expressions like `DATE_TRUNC('year', x) >= CAST('2021-01-01' AS DATE)`""" 818 comparison = expression.__class__ 819 820 if comparison not in DATETRUNC_COMPARISONS: 821 return expression 822 823 if isinstance(expression, exp.Binary): 824 l, r = expression.left, expression.right 825 826 if _is_datetrunc_predicate(l, r): 827 pass 828 elif _is_datetrunc_predicate(r, l): 829 comparison = INVERSE_COMPARISONS.get(comparison, comparison) 830 l, r = r, l 831 else: 832 return expression 833 834 l = t.cast(exp.DateTrunc, l) 835 unit = l.unit.name.lower() 836 date = extract_date(r) 837 838 if not date: 839 return expression 840 841 return DATETRUNC_BINARY_COMPARISONS[comparison](l.this, date, unit) or expression 842 elif isinstance(expression, exp.In): 843 l = expression.this 844 rs = expression.expressions 845 846 if rs and all(_is_datetrunc_predicate(l, r) for r in rs): 847 l = t.cast(exp.DateTrunc, l) 848 unit = l.unit.name.lower() 849 850 ranges = [] 851 for r in rs: 852 date = extract_date(r) 853 if not date: 854 return expression 855 drange = _datetrunc_range(date, unit) 856 if drange: 857 ranges.append(drange) 858 859 if not ranges: 860 return expression 861 862 ranges = merge_ranges(ranges) 863 864 return exp.or_(*[_datetrunc_eq_expression(l, drange) for drange in ranges], copy=False) 865 866 return expression 867 868 869# CROSS joins result in an empty table if the right table is empty. 870# So we can only simplify certain types of joins to CROSS. 871# Or in other words, LEFT JOIN x ON TRUE != CROSS JOIN x 872JOINS = { 873 ("", ""), 874 ("", "INNER"), 875 ("RIGHT", ""), 876 ("RIGHT", "OUTER"), 877} 878 879 880def remove_where_true(expression): 881 for where in expression.find_all(exp.Where): 882 if always_true(where.this): 883 where.parent.set("where", None) 884 for join in expression.find_all(exp.Join): 885 if ( 886 always_true(join.args.get("on")) 887 and not join.args.get("using") 888 and not join.args.get("method") 889 and (join.side, join.kind) in JOINS 890 ): 891 join.set("on", None) 892 join.set("side", None) 893 join.set("kind", "CROSS") 894 895 896def always_true(expression): 897 return (isinstance(expression, exp.Boolean) and expression.this) or isinstance( 898 expression, exp.Literal 899 ) 900 901 902def always_false(expression): 903 return is_false(expression) or is_null(expression) 904 905 906def is_complement(a, b): 907 return isinstance(b, exp.Not) and b.this == a 908 909 910def is_false(a: exp.Expression) -> bool: 911 return type(a) is exp.Boolean and not a.this 912 913 914def is_null(a: exp.Expression) -> bool: 915 return type(a) is exp.Null 916 917 918def eval_boolean(expression, a, b): 919 if isinstance(expression, (exp.EQ, exp.Is)): 920 return boolean_literal(a == b) 921 if isinstance(expression, exp.NEQ): 922 return boolean_literal(a != b) 923 if isinstance(expression, exp.GT): 924 return boolean_literal(a > b) 925 if isinstance(expression, exp.GTE): 926 return boolean_literal(a >= b) 927 if isinstance(expression, exp.LT): 928 return boolean_literal(a < b) 929 if isinstance(expression, exp.LTE): 930 return boolean_literal(a <= b) 931 return None 932 933 934def cast_as_date(value: t.Any) -> t.Optional[datetime.date]: 935 if isinstance(value, datetime.datetime): 936 return value.date() 937 if isinstance(value, datetime.date): 938 return value 939 try: 940 return datetime.datetime.fromisoformat(value).date() 941 except ValueError: 942 return None 943 944 945def cast_as_datetime(value: t.Any) -> t.Optional[datetime.datetime]: 946 if isinstance(value, datetime.datetime): 947 return value 948 if isinstance(value, datetime.date): 949 return datetime.datetime(year=value.year, month=value.month, day=value.day) 950 try: 951 return datetime.datetime.fromisoformat(value) 952 except ValueError: 953 return None 954 955 956def cast_value(value: t.Any, to: exp.DataType) -> t.Optional[t.Union[datetime.date, datetime.date]]: 957 if not value: 958 return None 959 if to.is_type(exp.DataType.Type.DATE): 960 return cast_as_date(value) 961 if to.is_type(*exp.DataType.TEMPORAL_TYPES): 962 return cast_as_datetime(value) 963 return None 964 965 966def extract_date(cast: exp.Expression) -> t.Optional[t.Union[datetime.date, datetime.date]]: 967 if isinstance(cast, exp.Cast): 968 to = cast.to 969 elif isinstance(cast, exp.TsOrDsToDate) and not cast.args.get("format"): 970 to = exp.DataType.build(exp.DataType.Type.DATE) 971 else: 972 return None 973 974 if isinstance(cast.this, exp.Literal): 975 value: t.Any = cast.this.name 976 elif isinstance(cast.this, (exp.Cast, exp.TsOrDsToDate)): 977 value = extract_date(cast.this) 978 else: 979 return None 980 return cast_value(value, to) 981 982 983def _is_date_literal(expression: exp.Expression) -> bool: 984 return extract_date(expression) is not None 985 986 987def extract_interval(expression): 988 n = int(expression.name) 989 unit = expression.text("unit").lower() 990 991 try: 992 return interval(unit, n) 993 except (UnsupportedUnit, ModuleNotFoundError): 994 return None 995 996 997def date_literal(date): 998 return exp.cast( 999 exp.Literal.string(date), 1000 exp.DataType.Type.DATETIME 1001 if isinstance(date, datetime.datetime) 1002 else exp.DataType.Type.DATE, 1003 ) 1004 1005 1006def interval(unit: str, n: int = 1): 1007 from dateutil.relativedelta import relativedelta 1008 1009 if unit == "year": 1010 return relativedelta(years=1 * n) 1011 if unit == "quarter": 1012 return relativedelta(months=3 * n) 1013 if unit == "month": 1014 return relativedelta(months=1 * n) 1015 if unit == "week": 1016 return relativedelta(weeks=1 * n) 1017 if unit == "day": 1018 return relativedelta(days=1 * n) 1019 if unit == "hour": 1020 return relativedelta(hours=1 * n) 1021 if unit == "minute": 1022 return relativedelta(minutes=1 * n) 1023 if unit == "second": 1024 return relativedelta(seconds=1 * n) 1025 1026 raise UnsupportedUnit(f"Unsupported unit: {unit}") 1027 1028 1029def date_floor(d: datetime.date, unit: str) -> datetime.date: 1030 if unit == "year": 1031 return d.replace(month=1, day=1) 1032 if unit == "quarter": 1033 if d.month <= 3: 1034 return d.replace(month=1, day=1) 1035 elif d.month <= 6: 1036 return d.replace(month=4, day=1) 1037 elif d.month <= 9: 1038 return d.replace(month=7, day=1) 1039 else: 1040 return d.replace(month=10, day=1) 1041 if unit == "month": 1042 return d.replace(month=d.month, day=1) 1043 if unit == "week": 1044 # Assuming week starts on Monday (0) and ends on Sunday (6) 1045 return d - datetime.timedelta(days=d.weekday()) 1046 if unit == "day": 1047 return d 1048 1049 raise UnsupportedUnit(f"Unsupported unit: {unit}") 1050 1051 1052def date_ceil(d: datetime.date, unit: str) -> datetime.date: 1053 floor = date_floor(d, unit) 1054 1055 if floor == d: 1056 return d 1057 1058 return floor + interval(unit) 1059 1060 1061def boolean_literal(condition): 1062 return exp.true() if condition else exp.false() 1063 1064 1065def _flat_simplify(expression, simplifier, root=True): 1066 if root or not expression.same_parent: 1067 operands = [] 1068 queue = deque(expression.flatten(unnest=False)) 1069 size = len(queue) 1070 1071 while queue: 1072 a = queue.popleft() 1073 1074 for b in queue: 1075 result = simplifier(expression, a, b) 1076 1077 if result and result is not expression: 1078 queue.remove(b) 1079 queue.appendleft(result) 1080 break 1081 else: 1082 operands.append(a) 1083 1084 if len(operands) < size: 1085 return functools.reduce( 1086 lambda a, b: expression.__class__(this=a, expression=b), operands 1087 ) 1088 return expression 1089 1090 1091def gen(expression: t.Any) -> str: 1092 """Simple pseudo sql generator for quickly generating sortable and uniq strings. 1093 1094 Sorting and deduping sql is a necessary step for optimization. Calling the actual 1095 generator is expensive so we have a bare minimum sql generator here. 1096 """ 1097 if expression is None: 1098 return "_" 1099 if is_iterable(expression): 1100 return ",".join(gen(e) for e in expression) 1101 if not isinstance(expression, exp.Expression): 1102 return str(expression) 1103 1104 etype = type(expression) 1105 if etype in GEN_MAP: 1106 return GEN_MAP[etype](expression) 1107 return f"{expression.key} {gen(expression.args.values())}" 1108 1109 1110GEN_MAP = { 1111 exp.Add: lambda e: _binary(e, "+"), 1112 exp.And: lambda e: _binary(e, "AND"), 1113 exp.Anonymous: lambda e: f"{e.this} {','.join(gen(e) for e in e.expressions)}", 1114 exp.Between: lambda e: f"{gen(e.this)} BETWEEN {gen(e.args.get('low'))} AND {gen(e.args.get('high'))}", 1115 exp.Boolean: lambda e: "TRUE" if e.this else "FALSE", 1116 exp.Bracket: lambda e: f"{gen(e.this)}[{gen(e.expressions)}]", 1117 exp.Column: lambda e: ".".join(gen(p) for p in e.parts), 1118 exp.DataType: lambda e: f"{e.this.name} {gen(tuple(e.args.values())[1:])}", 1119 exp.Div: lambda e: _binary(e, "/"), 1120 exp.Dot: lambda e: _binary(e, "."), 1121 exp.DPipe: lambda e: _binary(e, "||"), 1122 exp.SafeDPipe: lambda e: _binary(e, "||"), 1123 exp.EQ: lambda e: _binary(e, "="), 1124 exp.GT: lambda e: _binary(e, ">"), 1125 exp.GTE: lambda e: _binary(e, ">="), 1126 exp.Identifier: lambda e: f'"{e.name}"' if e.quoted else e.name, 1127 exp.ILike: lambda e: _binary(e, "ILIKE"), 1128 exp.In: lambda e: f"{gen(e.this)} IN ({gen(tuple(e.args.values())[1:])})", 1129 exp.Is: lambda e: _binary(e, "IS"), 1130 exp.Like: lambda e: _binary(e, "LIKE"), 1131 exp.Literal: lambda e: f"'{e.name}'" if e.is_string else e.name, 1132 exp.LT: lambda e: _binary(e, "<"), 1133 exp.LTE: lambda e: _binary(e, "<="), 1134 exp.Mod: lambda e: _binary(e, "%"), 1135 exp.Mul: lambda e: _binary(e, "*"), 1136 exp.Neg: lambda e: _unary(e, "-"), 1137 exp.NEQ: lambda e: _binary(e, "<>"), 1138 exp.Not: lambda e: _unary(e, "NOT"), 1139 exp.Null: lambda e: "NULL", 1140 exp.Or: lambda e: _binary(e, "OR"), 1141 exp.Paren: lambda e: f"({gen(e.this)})", 1142 exp.Sub: lambda e: _binary(e, "-"), 1143 exp.Subquery: lambda e: f"({gen(e.args.values())})", 1144 exp.Table: lambda e: gen(e.args.values()), 1145 exp.Var: lambda e: e.name, 1146} 1147 1148 1149def _binary(e: exp.Binary, op: str) -> str: 1150 return f"{gen(e.left)} {op} {gen(e.right)}" 1151 1152 1153def _unary(e: exp.Unary, op: str) -> str: 1154 return f"{op} {gen(e.this)}"
Common base class for all non-exit exceptions.
Inherited Members
- builtins.Exception
- Exception
- builtins.BaseException
- with_traceback
- args
22def simplify(expression, constant_propagation=False): 23 """ 24 Rewrite sqlglot AST to simplify expressions. 25 26 Example: 27 >>> import sqlglot 28 >>> expression = sqlglot.parse_one("TRUE AND TRUE") 29 >>> simplify(expression).sql() 30 'TRUE' 31 32 Args: 33 expression (sqlglot.Expression): expression to simplify 34 constant_propagation: whether or not the constant propagation rule should be used 35 36 Returns: 37 sqlglot.Expression: simplified expression 38 """ 39 40 # group by expressions cannot be simplified, for example 41 # select x + 1 + 1 FROM y GROUP BY x + 1 + 1 42 # the projection must exactly match the group by key 43 for group in expression.find_all(exp.Group): 44 select = group.parent 45 groups = set(group.expressions) 46 group.meta[FINAL] = True 47 48 for e in select.selects: 49 for node, *_ in e.walk(): 50 if node in groups: 51 e.meta[FINAL] = True 52 break 53 54 having = select.args.get("having") 55 if having: 56 for node, *_ in having.walk(): 57 if node in groups: 58 having.meta[FINAL] = True 59 break 60 61 def _simplify(expression, root=True): 62 if expression.meta.get(FINAL): 63 return expression 64 65 # Pre-order transformations 66 node = expression 67 node = rewrite_between(node) 68 node = uniq_sort(node, root) 69 node = absorb_and_eliminate(node, root) 70 node = simplify_concat(node) 71 node = simplify_conditionals(node) 72 73 if constant_propagation: 74 node = propagate_constants(node, root) 75 76 exp.replace_children(node, lambda e: _simplify(e, False)) 77 78 # Post-order transformations 79 node = simplify_not(node) 80 node = flatten(node) 81 node = simplify_connectors(node, root) 82 node = remove_complements(node, root) 83 node = simplify_coalesce(node) 84 node.parent = expression.parent 85 node = simplify_literals(node, root) 86 node = simplify_equality(node) 87 node = simplify_parens(node) 88 node = simplify_datetrunc_predicate(node) 89 90 if root: 91 expression.replace(node) 92 93 return node 94 95 expression = while_changing(expression, _simplify) 96 remove_where_true(expression) 97 return expression
Rewrite sqlglot AST to simplify expressions.
Example:
>>> import sqlglot >>> expression = sqlglot.parse_one("TRUE AND TRUE") >>> simplify(expression).sql() 'TRUE'
Arguments:
- expression (sqlglot.Expression): expression to simplify
- constant_propagation: whether or not the constant propagation rule should be used
Returns:
sqlglot.Expression: simplified expression
100def catch(*exceptions): 101 """Decorator that ignores a simplification function if any of `exceptions` are raised""" 102 103 def decorator(func): 104 def wrapped(expression, *args, **kwargs): 105 try: 106 return func(expression, *args, **kwargs) 107 except exceptions: 108 return expression 109 110 return wrapped 111 112 return decorator
Decorator that ignores a simplification function if any of exceptions
are raised
115def rewrite_between(expression: exp.Expression) -> exp.Expression: 116 """Rewrite x between y and z to x >= y AND x <= z. 117 118 This is done because comparison simplification is only done on lt/lte/gt/gte. 119 """ 120 if isinstance(expression, exp.Between): 121 return exp.and_( 122 exp.GTE(this=expression.this.copy(), expression=expression.args["low"]), 123 exp.LTE(this=expression.this.copy(), expression=expression.args["high"]), 124 copy=False, 125 ) 126 return expression
Rewrite x between y and z to x >= y AND x <= z.
This is done because comparison simplification is only done on lt/lte/gt/gte.
129def simplify_not(expression): 130 """ 131 Demorgan's Law 132 NOT (x OR y) -> NOT x AND NOT y 133 NOT (x AND y) -> NOT x OR NOT y 134 """ 135 if isinstance(expression, exp.Not): 136 if is_null(expression.this): 137 return exp.null() 138 if isinstance(expression.this, exp.Paren): 139 condition = expression.this.unnest() 140 if isinstance(condition, exp.And): 141 return exp.or_( 142 exp.not_(condition.left, copy=False), 143 exp.not_(condition.right, copy=False), 144 copy=False, 145 ) 146 if isinstance(condition, exp.Or): 147 return exp.and_( 148 exp.not_(condition.left, copy=False), 149 exp.not_(condition.right, copy=False), 150 copy=False, 151 ) 152 if is_null(condition): 153 return exp.null() 154 if always_true(expression.this): 155 return exp.false() 156 if is_false(expression.this): 157 return exp.true() 158 if isinstance(expression.this, exp.Not): 159 # double negation 160 # NOT NOT x -> x 161 return expression.this.this 162 return expression
Demorgan's Law NOT (x OR y) -> NOT x AND NOT y NOT (x AND y) -> NOT x OR NOT y
165def flatten(expression): 166 """ 167 A AND (B AND C) -> A AND B AND C 168 A OR (B OR C) -> A OR B OR C 169 """ 170 if isinstance(expression, exp.Connector): 171 for node in expression.args.values(): 172 child = node.unnest() 173 if isinstance(child, expression.__class__): 174 node.replace(child) 175 return expression
A AND (B AND C) -> A AND B AND C A OR (B OR C) -> A OR B OR C
178def simplify_connectors(expression, root=True): 179 def _simplify_connectors(expression, left, right): 180 if left == right: 181 return left 182 if isinstance(expression, exp.And): 183 if is_false(left) or is_false(right): 184 return exp.false() 185 if is_null(left) or is_null(right): 186 return exp.null() 187 if always_true(left) and always_true(right): 188 return exp.true() 189 if always_true(left): 190 return right 191 if always_true(right): 192 return left 193 return _simplify_comparison(expression, left, right) 194 elif isinstance(expression, exp.Or): 195 if always_true(left) or always_true(right): 196 return exp.true() 197 if is_false(left) and is_false(right): 198 return exp.false() 199 if ( 200 (is_null(left) and is_null(right)) 201 or (is_null(left) and is_false(right)) 202 or (is_false(left) and is_null(right)) 203 ): 204 return exp.null() 205 if is_false(left): 206 return right 207 if is_false(right): 208 return left 209 return _simplify_comparison(expression, left, right, or_=True) 210 211 if isinstance(expression, exp.Connector): 212 return _flat_simplify(expression, _simplify_connectors, root) 213 return expression
296def remove_complements(expression, root=True): 297 """ 298 Removing complements. 299 300 A AND NOT A -> FALSE 301 A OR NOT A -> TRUE 302 """ 303 if isinstance(expression, exp.Connector) and (root or not expression.same_parent): 304 complement = exp.false() if isinstance(expression, exp.And) else exp.true() 305 306 for a, b in itertools.permutations(expression.flatten(), 2): 307 if is_complement(a, b): 308 return complement 309 return expression
Removing complements.
A AND NOT A -> FALSE A OR NOT A -> TRUE
312def uniq_sort(expression, root=True): 313 """ 314 Uniq and sort a connector. 315 316 C AND A AND B AND B -> A AND B AND C 317 """ 318 if isinstance(expression, exp.Connector) and (root or not expression.same_parent): 319 result_func = exp.and_ if isinstance(expression, exp.And) else exp.or_ 320 flattened = tuple(expression.flatten()) 321 deduped = {gen(e): e for e in flattened} 322 arr = tuple(deduped.items()) 323 324 # check if the operands are already sorted, if not sort them 325 # A AND C AND B -> A AND B AND C 326 for i, (sql, e) in enumerate(arr[1:]): 327 if sql < arr[i][0]: 328 expression = result_func(*(e for _, e in sorted(arr)), copy=False) 329 break 330 else: 331 # we didn't have to sort but maybe we need to dedup 332 if len(deduped) < len(flattened): 333 expression = result_func(*deduped.values(), copy=False) 334 335 return expression
Uniq and sort a connector.
C AND A AND B AND B -> A AND B AND C
338def absorb_and_eliminate(expression, root=True): 339 """ 340 absorption: 341 A AND (A OR B) -> A 342 A OR (A AND B) -> A 343 A AND (NOT A OR B) -> A AND B 344 A OR (NOT A AND B) -> A OR B 345 elimination: 346 (A AND B) OR (A AND NOT B) -> A 347 (A OR B) AND (A OR NOT B) -> A 348 """ 349 if isinstance(expression, exp.Connector) and (root or not expression.same_parent): 350 kind = exp.Or if isinstance(expression, exp.And) else exp.And 351 352 for a, b in itertools.permutations(expression.flatten(), 2): 353 if isinstance(a, kind): 354 aa, ab = a.unnest_operands() 355 356 # absorb 357 if is_complement(b, aa): 358 aa.replace(exp.true() if kind == exp.And else exp.false()) 359 elif is_complement(b, ab): 360 ab.replace(exp.true() if kind == exp.And else exp.false()) 361 elif (set(b.flatten()) if isinstance(b, kind) else {b}) < set(a.flatten()): 362 a.replace(exp.false() if kind == exp.And else exp.true()) 363 elif isinstance(b, kind): 364 # eliminate 365 rhs = b.unnest_operands() 366 ba, bb = rhs 367 368 if aa in rhs and (is_complement(ab, ba) or is_complement(ab, bb)): 369 a.replace(aa) 370 b.replace(aa) 371 elif ab in rhs and (is_complement(aa, ba) or is_complement(aa, bb)): 372 a.replace(ab) 373 b.replace(ab) 374 375 return expression
absorption: A AND (A OR B) -> A A OR (A AND B) -> A A AND (NOT A OR B) -> A AND B A OR (NOT A AND B) -> A OR B elimination: (A AND B) OR (A AND NOT B) -> A (A OR B) AND (A OR NOT B) -> A
378def propagate_constants(expression, root=True): 379 """ 380 Propagate constants for conjunctions in DNF: 381 382 SELECT * FROM t WHERE a = b AND b = 5 becomes 383 SELECT * FROM t WHERE a = 5 AND b = 5 384 385 Reference: https://www.sqlite.org/optoverview.html 386 """ 387 388 if ( 389 isinstance(expression, exp.And) 390 and (root or not expression.same_parent) 391 and sqlglot.optimizer.normalize.normalized(expression, dnf=True) 392 ): 393 constant_mapping = {} 394 for expr, *_ in walk_in_scope(expression, prune=lambda node, *_: isinstance(node, exp.If)): 395 if isinstance(expr, exp.EQ): 396 l, r = expr.left, expr.right 397 398 # TODO: create a helper that can be used to detect nested literal expressions such 399 # as CAST(123456 AS BIGINT), since we usually want to treat those as literals too 400 if isinstance(l, exp.Column) and isinstance(r, exp.Literal): 401 pass 402 elif isinstance(r, exp.Column) and isinstance(l, exp.Literal): 403 l, r = r, l 404 else: 405 continue 406 407 constant_mapping[l] = (id(l), r) 408 409 if constant_mapping: 410 for column in find_all_in_scope(expression, exp.Column): 411 parent = column.parent 412 column_id, constant = constant_mapping.get(column) or (None, None) 413 if ( 414 column_id is not None 415 and id(column) != column_id 416 and not (isinstance(parent, exp.Is) and isinstance(parent.expression, exp.Null)) 417 ): 418 column.replace(constant.copy()) 419 420 return expression
Propagate constants for conjunctions in DNF:
SELECT * FROM t WHERE a = b AND b = 5 becomes SELECT * FROM t WHERE a = 5 AND b = 5
Reference: https://www.sqlite.org/optoverview.html
104 def wrapped(expression, *args, **kwargs): 105 try: 106 return func(expression, *args, **kwargs) 107 except exceptions: 108 return expression
Use the subtraction and addition properties of equality to simplify expressions:
x + 1 = 3 becomes x = 2
There are two binary operations in the above expression: + and = Here's how we reference all the operands in the code below:
l r
x + 1 = 3
a b
499def simplify_literals(expression, root=True): 500 if isinstance(expression, exp.Binary) and not isinstance(expression, exp.Connector): 501 return _flat_simplify(expression, _simplify_binary, root) 502 503 if isinstance(expression, exp.Neg): 504 this = expression.this 505 if this.is_number: 506 value = this.name 507 if value[0] == "-": 508 return exp.Literal.number(value[1:]) 509 return exp.Literal.number(f"-{value}") 510 511 return expression
580def simplify_parens(expression): 581 if not isinstance(expression, exp.Paren): 582 return expression 583 584 this = expression.this 585 parent = expression.parent 586 587 if not isinstance(this, exp.Select) and ( 588 not isinstance(parent, (exp.Condition, exp.Binary)) 589 or isinstance(parent, exp.Paren) 590 or not isinstance(this, exp.Binary) 591 or (isinstance(this, exp.Predicate) and not isinstance(parent, exp.Predicate)) 592 or (isinstance(this, exp.Add) and isinstance(parent, exp.Add)) 593 or (isinstance(this, exp.Mul) and isinstance(parent, exp.Mul)) 594 or (isinstance(this, exp.Mul) and isinstance(parent, (exp.Add, exp.Sub))) 595 ): 596 return this 597 return expression
620def simplify_coalesce(expression): 621 # COALESCE(x) -> x 622 if ( 623 isinstance(expression, exp.Coalesce) 624 and (not expression.expressions or _is_nonnull_constant(expression.this)) 625 # COALESCE is also used as a Spark partitioning hint 626 and not isinstance(expression.parent, exp.Hint) 627 ): 628 return expression.this 629 630 if not isinstance(expression, COMPARISONS): 631 return expression 632 633 if isinstance(expression.left, exp.Coalesce): 634 coalesce = expression.left 635 other = expression.right 636 elif isinstance(expression.right, exp.Coalesce): 637 coalesce = expression.right 638 other = expression.left 639 else: 640 return expression 641 642 # This transformation is valid for non-constants, 643 # but it really only does anything if they are both constants. 644 if not _is_constant(other): 645 return expression 646 647 # Find the first constant arg 648 for arg_index, arg in enumerate(coalesce.expressions): 649 if _is_constant(other): 650 break 651 else: 652 return expression 653 654 coalesce.set("expressions", coalesce.expressions[:arg_index]) 655 656 # Remove the COALESCE function. This is an optimization, skipping a simplify iteration, 657 # since we already remove COALESCE at the top of this function. 658 coalesce = coalesce if coalesce.expressions else coalesce.this 659 660 # This expression is more complex than when we started, but it will get simplified further 661 return exp.paren( 662 exp.or_( 663 exp.and_( 664 coalesce.is_(exp.null()).not_(copy=False), 665 expression.copy(), 666 copy=False, 667 ), 668 exp.and_( 669 coalesce.is_(exp.null()), 670 type(expression)(this=arg.copy(), expression=other.copy()), 671 copy=False, 672 ), 673 copy=False, 674 ) 675 )
682def simplify_concat(expression): 683 """Reduces all groups that contain string literals by concatenating them.""" 684 if not isinstance(expression, CONCATS) or ( 685 # We can't reduce a CONCAT_WS call if we don't statically know the separator 686 isinstance(expression, exp.ConcatWs) 687 and not expression.expressions[0].is_string 688 ): 689 return expression 690 691 if isinstance(expression, exp.ConcatWs): 692 sep_expr, *expressions = expression.expressions 693 sep = sep_expr.name 694 concat_type = exp.ConcatWs 695 else: 696 expressions = expression.expressions 697 sep = "" 698 concat_type = exp.SafeConcat if isinstance(expression, SAFE_CONCATS) else exp.Concat 699 700 new_args = [] 701 for is_string_group, group in itertools.groupby( 702 expressions or expression.flatten(), lambda e: e.is_string 703 ): 704 if is_string_group: 705 new_args.append(exp.Literal.string(sep.join(string.name for string in group))) 706 else: 707 new_args.extend(group) 708 709 if len(new_args) == 1 and new_args[0].is_string: 710 return new_args[0] 711 712 if concat_type is exp.ConcatWs: 713 new_args = [sep_expr] + new_args 714 715 return concat_type(expressions=new_args)
Reduces all groups that contain string literals by concatenating them.
718def simplify_conditionals(expression): 719 """Simplifies expressions like IF, CASE if their condition is statically known.""" 720 if isinstance(expression, exp.Case): 721 this = expression.this 722 for case in expression.args["ifs"]: 723 cond = case.this 724 if this: 725 # Convert CASE x WHEN matching_value ... to CASE WHEN x = matching_value ... 726 cond = cond.replace(this.pop().eq(cond)) 727 728 if always_true(cond): 729 return case.args["true"] 730 731 if always_false(cond): 732 case.pop() 733 if not expression.args["ifs"]: 734 return expression.args.get("default") or exp.null() 735 elif isinstance(expression, exp.If) and not isinstance(expression.parent, exp.Case): 736 if always_true(expression.this): 737 return expression.args["true"] 738 if always_false(expression.this): 739 return expression.args.get("false") or exp.null() 740 741 return expression
Simplifies expressions like IF, CASE if their condition is statically known.
104 def wrapped(expression, *args, **kwargs): 105 try: 106 return func(expression, *args, **kwargs) 107 except exceptions: 108 return expression
Simplify expressions like DATE_TRUNC('year', x) >= CAST('2021-01-01' AS DATE)
881def remove_where_true(expression): 882 for where in expression.find_all(exp.Where): 883 if always_true(where.this): 884 where.parent.set("where", None) 885 for join in expression.find_all(exp.Join): 886 if ( 887 always_true(join.args.get("on")) 888 and not join.args.get("using") 889 and not join.args.get("method") 890 and (join.side, join.kind) in JOINS 891 ): 892 join.set("on", None) 893 join.set("side", None) 894 join.set("kind", "CROSS")
919def eval_boolean(expression, a, b): 920 if isinstance(expression, (exp.EQ, exp.Is)): 921 return boolean_literal(a == b) 922 if isinstance(expression, exp.NEQ): 923 return boolean_literal(a != b) 924 if isinstance(expression, exp.GT): 925 return boolean_literal(a > b) 926 if isinstance(expression, exp.GTE): 927 return boolean_literal(a >= b) 928 if isinstance(expression, exp.LT): 929 return boolean_literal(a < b) 930 if isinstance(expression, exp.LTE): 931 return boolean_literal(a <= b) 932 return None
946def cast_as_datetime(value: t.Any) -> t.Optional[datetime.datetime]: 947 if isinstance(value, datetime.datetime): 948 return value 949 if isinstance(value, datetime.date): 950 return datetime.datetime(year=value.year, month=value.month, day=value.day) 951 try: 952 return datetime.datetime.fromisoformat(value) 953 except ValueError: 954 return None
957def cast_value(value: t.Any, to: exp.DataType) -> t.Optional[t.Union[datetime.date, datetime.date]]: 958 if not value: 959 return None 960 if to.is_type(exp.DataType.Type.DATE): 961 return cast_as_date(value) 962 if to.is_type(*exp.DataType.TEMPORAL_TYPES): 963 return cast_as_datetime(value) 964 return None
967def extract_date(cast: exp.Expression) -> t.Optional[t.Union[datetime.date, datetime.date]]: 968 if isinstance(cast, exp.Cast): 969 to = cast.to 970 elif isinstance(cast, exp.TsOrDsToDate) and not cast.args.get("format"): 971 to = exp.DataType.build(exp.DataType.Type.DATE) 972 else: 973 return None 974 975 if isinstance(cast.this, exp.Literal): 976 value: t.Any = cast.this.name 977 elif isinstance(cast.this, (exp.Cast, exp.TsOrDsToDate)): 978 value = extract_date(cast.this) 979 else: 980 return None 981 return cast_value(value, to)
1007def interval(unit: str, n: int = 1): 1008 from dateutil.relativedelta import relativedelta 1009 1010 if unit == "year": 1011 return relativedelta(years=1 * n) 1012 if unit == "quarter": 1013 return relativedelta(months=3 * n) 1014 if unit == "month": 1015 return relativedelta(months=1 * n) 1016 if unit == "week": 1017 return relativedelta(weeks=1 * n) 1018 if unit == "day": 1019 return relativedelta(days=1 * n) 1020 if unit == "hour": 1021 return relativedelta(hours=1 * n) 1022 if unit == "minute": 1023 return relativedelta(minutes=1 * n) 1024 if unit == "second": 1025 return relativedelta(seconds=1 * n) 1026 1027 raise UnsupportedUnit(f"Unsupported unit: {unit}")
1030def date_floor(d: datetime.date, unit: str) -> datetime.date: 1031 if unit == "year": 1032 return d.replace(month=1, day=1) 1033 if unit == "quarter": 1034 if d.month <= 3: 1035 return d.replace(month=1, day=1) 1036 elif d.month <= 6: 1037 return d.replace(month=4, day=1) 1038 elif d.month <= 9: 1039 return d.replace(month=7, day=1) 1040 else: 1041 return d.replace(month=10, day=1) 1042 if unit == "month": 1043 return d.replace(month=d.month, day=1) 1044 if unit == "week": 1045 # Assuming week starts on Monday (0) and ends on Sunday (6) 1046 return d - datetime.timedelta(days=d.weekday()) 1047 if unit == "day": 1048 return d 1049 1050 raise UnsupportedUnit(f"Unsupported unit: {unit}")
1092def gen(expression: t.Any) -> str: 1093 """Simple pseudo sql generator for quickly generating sortable and uniq strings. 1094 1095 Sorting and deduping sql is a necessary step for optimization. Calling the actual 1096 generator is expensive so we have a bare minimum sql generator here. 1097 """ 1098 if expression is None: 1099 return "_" 1100 if is_iterable(expression): 1101 return ",".join(gen(e) for e in expression) 1102 if not isinstance(expression, exp.Expression): 1103 return str(expression) 1104 1105 etype = type(expression) 1106 if etype in GEN_MAP: 1107 return GEN_MAP[etype](expression) 1108 return f"{expression.key} {gen(expression.args.values())}"
Simple pseudo sql generator for quickly generating sortable and uniq strings.
Sorting and deduping sql is a necessary step for optimization. Calling the actual generator is expensive so we have a bare minimum sql generator here.