sqlglot.optimizer.qualify_columns
1from __future__ import annotations 2 3import itertools 4import typing as t 5 6from sqlglot import alias, exp 7from sqlglot._typing import E 8from sqlglot.dialects.dialect import Dialect, DialectType 9from sqlglot.errors import OptimizeError 10from sqlglot.helper import seq_get 11from sqlglot.optimizer.scope import Scope, traverse_scope, walk_in_scope 12from sqlglot.schema import Schema, ensure_schema 13 14 15def qualify_columns( 16 expression: exp.Expression, 17 schema: t.Dict | Schema, 18 expand_alias_refs: bool = True, 19 infer_schema: t.Optional[bool] = None, 20) -> exp.Expression: 21 """ 22 Rewrite sqlglot AST to have fully qualified columns. 23 24 Example: 25 >>> import sqlglot 26 >>> schema = {"tbl": {"col": "INT"}} 27 >>> expression = sqlglot.parse_one("SELECT col FROM tbl") 28 >>> qualify_columns(expression, schema).sql() 29 'SELECT tbl.col AS col FROM tbl' 30 31 Args: 32 expression: expression to qualify 33 schema: Database schema 34 expand_alias_refs: whether or not to expand references to aliases 35 infer_schema: whether or not to infer the schema if missing 36 Returns: 37 sqlglot.Expression: qualified expression 38 """ 39 schema = ensure_schema(schema) 40 infer_schema = schema.empty if infer_schema is None else infer_schema 41 42 for scope in traverse_scope(expression): 43 resolver = Resolver(scope, schema, infer_schema=infer_schema) 44 _pop_table_column_aliases(scope.ctes) 45 _pop_table_column_aliases(scope.derived_tables) 46 using_column_tables = _expand_using(scope, resolver) 47 48 if schema.empty and expand_alias_refs: 49 _expand_alias_refs(scope, resolver) 50 51 _qualify_columns(scope, resolver) 52 53 if not schema.empty and expand_alias_refs: 54 _expand_alias_refs(scope, resolver) 55 56 if not isinstance(scope.expression, exp.UDTF): 57 _expand_stars(scope, resolver, using_column_tables) 58 _qualify_outputs(scope) 59 _expand_group_by(scope) 60 _expand_order_by(scope, resolver) 61 62 return expression 63 64 65def validate_qualify_columns(expression: E) -> E: 66 """Raise an `OptimizeError` if any columns aren't qualified""" 67 unqualified_columns = [] 68 for scope in traverse_scope(expression): 69 if isinstance(scope.expression, exp.Select): 70 unqualified_columns.extend(scope.unqualified_columns) 71 if scope.external_columns and not scope.is_correlated_subquery and not scope.pivots: 72 column = scope.external_columns[0] 73 raise OptimizeError( 74 f"""Column '{column}' could not be resolved{f" for table: '{column.table}'" if column.table else ''}""" 75 ) 76 77 if unqualified_columns: 78 raise OptimizeError(f"Ambiguous columns: {unqualified_columns}") 79 return expression 80 81 82def _pop_table_column_aliases(derived_tables: t.List[exp.CTE | exp.Subquery]) -> None: 83 """ 84 Remove table column aliases. 85 86 (e.g. SELECT ... FROM (SELECT ...) AS foo(col1, col2) 87 """ 88 for derived_table in derived_tables: 89 table_alias = derived_table.args.get("alias") 90 if table_alias: 91 table_alias.args.pop("columns", None) 92 93 94def _expand_using(scope: Scope, resolver: Resolver) -> t.Dict[str, t.Any]: 95 joins = list(scope.find_all(exp.Join)) 96 names = {join.alias_or_name for join in joins} 97 ordered = [key for key in scope.selected_sources if key not in names] 98 99 # Mapping of automatically joined column names to an ordered set of source names (dict). 100 column_tables: t.Dict[str, t.Dict[str, t.Any]] = {} 101 102 for join in joins: 103 using = join.args.get("using") 104 105 if not using: 106 continue 107 108 join_table = join.alias_or_name 109 110 columns = {} 111 112 for k in scope.selected_sources: 113 if k in ordered: 114 for column in resolver.get_source_columns(k): 115 if column not in columns: 116 columns[column] = k 117 118 source_table = ordered[-1] 119 ordered.append(join_table) 120 join_columns = resolver.get_source_columns(join_table) 121 conditions = [] 122 123 for identifier in using: 124 identifier = identifier.name 125 table = columns.get(identifier) 126 127 if not table or identifier not in join_columns: 128 if columns and join_columns: 129 raise OptimizeError(f"Cannot automatically join: {identifier}") 130 131 table = table or source_table 132 conditions.append( 133 exp.condition( 134 exp.EQ( 135 this=exp.column(identifier, table=table), 136 expression=exp.column(identifier, table=join_table), 137 ) 138 ) 139 ) 140 141 # Set all values in the dict to None, because we only care about the key ordering 142 tables = column_tables.setdefault(identifier, {}) 143 if table not in tables: 144 tables[table] = None 145 if join_table not in tables: 146 tables[join_table] = None 147 148 join.args.pop("using") 149 join.set("on", exp.and_(*conditions, copy=False)) 150 151 if column_tables: 152 for column in scope.columns: 153 if not column.table and column.name in column_tables: 154 tables = column_tables[column.name] 155 coalesce = [exp.column(column.name, table=table) for table in tables] 156 replacement = exp.Coalesce(this=coalesce[0], expressions=coalesce[1:]) 157 158 # Ensure selects keep their output name 159 if isinstance(column.parent, exp.Select): 160 replacement = alias(replacement, alias=column.name, copy=False) 161 162 scope.replace(column, replacement) 163 164 return column_tables 165 166 167def _expand_alias_refs(scope: Scope, resolver: Resolver) -> None: 168 expression = scope.expression 169 170 if not isinstance(expression, exp.Select): 171 return 172 173 alias_to_expression: t.Dict[str, exp.Expression] = {} 174 175 def replace_columns(node: t.Optional[exp.Expression], resolve_table: bool = False) -> None: 176 if not node: 177 return 178 179 for column, *_ in walk_in_scope(node): 180 if not isinstance(column, exp.Column): 181 continue 182 table = resolver.get_table(column.name) if resolve_table and not column.table else None 183 alias_expr = alias_to_expression.get(column.name) 184 double_agg = ( 185 (alias_expr.find(exp.AggFunc) and column.find_ancestor(exp.AggFunc)) 186 if alias_expr 187 else False 188 ) 189 190 if table and (not alias_expr or double_agg): 191 column.set("table", table) 192 elif not column.table and alias_expr and not double_agg: 193 column.replace(alias_expr.copy()) 194 195 for projection in scope.selects: 196 replace_columns(projection) 197 198 if isinstance(projection, exp.Alias): 199 alias_to_expression[projection.alias] = projection.this 200 201 replace_columns(expression.args.get("where")) 202 replace_columns(expression.args.get("group")) 203 replace_columns(expression.args.get("having"), resolve_table=True) 204 replace_columns(expression.args.get("qualify"), resolve_table=True) 205 scope.clear_cache() 206 207 208def _expand_group_by(scope: Scope): 209 expression = scope.expression 210 group = expression.args.get("group") 211 if not group: 212 return 213 214 group.set("expressions", _expand_positional_references(scope, group.expressions)) 215 expression.set("group", group) 216 217 # group by expressions cannot be simplified, for example 218 # select x + 1 + 1 FROM y GROUP BY x + 1 + 1 219 # the projection must exactly match the group by key 220 groups = set(group.expressions) 221 group.meta["final"] = True 222 223 for e in expression.selects: 224 for node, *_ in e.walk(): 225 if node in groups: 226 e.meta["final"] = True 227 break 228 229 having = expression.args.get("having") 230 if having: 231 for node, *_ in having.walk(): 232 if node in groups: 233 having.meta["final"] = True 234 break 235 236 237def _expand_order_by(scope: Scope, resolver: Resolver): 238 order = scope.expression.args.get("order") 239 if not order: 240 return 241 242 ordereds = order.expressions 243 for ordered, new_expression in zip( 244 ordereds, 245 _expand_positional_references(scope, (o.this for o in ordereds)), 246 ): 247 for agg in ordered.find_all(exp.AggFunc): 248 for col in agg.find_all(exp.Column): 249 if not col.table: 250 col.set("table", resolver.get_table(col.name)) 251 252 ordered.set("this", new_expression) 253 254 if scope.expression.args.get("group"): 255 selects = {s.this: exp.column(s.alias_or_name) for s in scope.selects} 256 257 for ordered in ordereds: 258 ordered.set("this", selects.get(ordered.this, ordered.this)) 259 260 261def _expand_positional_references(scope: Scope, expressions: t.Iterable[E]) -> t.List[E]: 262 new_nodes = [] 263 for node in expressions: 264 if node.is_int: 265 try: 266 select = scope.selects[int(node.name) - 1] 267 except IndexError: 268 raise OptimizeError(f"Unknown output column: {node.name}") 269 if isinstance(select, exp.Alias): 270 select = select.this 271 new_nodes.append(select.copy()) 272 scope.clear_cache() 273 else: 274 new_nodes.append(node) 275 276 return new_nodes 277 278 279def _qualify_columns(scope: Scope, resolver: Resolver) -> None: 280 """Disambiguate columns, ensuring each column specifies a source""" 281 for column in scope.columns: 282 column_table = column.table 283 column_name = column.name 284 285 if column_table and column_table in scope.sources: 286 source_columns = resolver.get_source_columns(column_table) 287 if source_columns and column_name not in source_columns and "*" not in source_columns: 288 raise OptimizeError(f"Unknown column: {column_name}") 289 290 if not column_table: 291 if scope.pivots and not column.find_ancestor(exp.Pivot): 292 # If the column is under the Pivot expression, we need to qualify it 293 # using the name of the pivoted source instead of the pivot's alias 294 column.set("table", exp.to_identifier(scope.pivots[0].alias)) 295 continue 296 297 column_table = resolver.get_table(column_name) 298 299 # column_table can be a '' because bigquery unnest has no table alias 300 if column_table: 301 column.set("table", column_table) 302 elif column_table not in scope.sources and ( 303 not scope.parent or column_table not in scope.parent.sources 304 ): 305 # structs are used like tables (e.g. "struct"."field"), so they need to be qualified 306 # separately and represented as dot(dot(...(<table>.<column>, field1), field2, ...)) 307 308 root, *parts = column.parts 309 310 if root.name in scope.sources: 311 # struct is already qualified, but we still need to change the AST representation 312 column_table = root 313 root, *parts = parts 314 else: 315 column_table = resolver.get_table(root.name) 316 317 if column_table: 318 column.replace(exp.Dot.build([exp.column(root, table=column_table), *parts])) 319 320 for pivot in scope.pivots: 321 for column in pivot.find_all(exp.Column): 322 if not column.table and column.name in resolver.all_columns: 323 column_table = resolver.get_table(column.name) 324 if column_table: 325 column.set("table", column_table) 326 327 328def _expand_stars( 329 scope: Scope, resolver: Resolver, using_column_tables: t.Dict[str, t.Any] 330) -> None: 331 """Expand stars to lists of column selections""" 332 333 new_selections = [] 334 except_columns: t.Dict[int, t.Set[str]] = {} 335 replace_columns: t.Dict[int, t.Dict[str, str]] = {} 336 coalesced_columns = set() 337 338 # TODO: handle optimization of multiple PIVOTs (and possibly UNPIVOTs) in the future 339 pivot_columns = None 340 pivot_output_columns = None 341 pivot = t.cast(t.Optional[exp.Pivot], seq_get(scope.pivots, 0)) 342 343 has_pivoted_source = pivot and not pivot.args.get("unpivot") 344 if pivot and has_pivoted_source: 345 pivot_columns = set(col.output_name for col in pivot.find_all(exp.Column)) 346 347 pivot_output_columns = [col.output_name for col in pivot.args.get("columns", [])] 348 if not pivot_output_columns: 349 pivot_output_columns = [col.alias_or_name for col in pivot.expressions] 350 351 for expression in scope.selects: 352 if isinstance(expression, exp.Star): 353 tables = list(scope.selected_sources) 354 _add_except_columns(expression, tables, except_columns) 355 _add_replace_columns(expression, tables, replace_columns) 356 elif expression.is_star: 357 tables = [expression.table] 358 _add_except_columns(expression.this, tables, except_columns) 359 _add_replace_columns(expression.this, tables, replace_columns) 360 else: 361 new_selections.append(expression) 362 continue 363 364 for table in tables: 365 if table not in scope.sources: 366 raise OptimizeError(f"Unknown table: {table}") 367 368 columns = resolver.get_source_columns(table, only_visible=True) 369 370 # The _PARTITIONTIME and _PARTITIONDATE pseudo-columns are not returned by a SELECT * statement 371 # https://cloud.google.com/bigquery/docs/querying-partitioned-tables#query_an_ingestion-time_partitioned_table 372 if resolver.schema.dialect == "bigquery": 373 columns = [ 374 name 375 for name in columns 376 if name.upper() not in ("_PARTITIONTIME", "_PARTITIONDATE") 377 ] 378 379 if columns and "*" not in columns: 380 if pivot and has_pivoted_source and pivot_columns and pivot_output_columns: 381 implicit_columns = [col for col in columns if col not in pivot_columns] 382 new_selections.extend( 383 exp.alias_(exp.column(name, table=pivot.alias), name, copy=False) 384 for name in implicit_columns + pivot_output_columns 385 ) 386 continue 387 388 table_id = id(table) 389 for name in columns: 390 if name in using_column_tables and table in using_column_tables[name]: 391 if name in coalesced_columns: 392 continue 393 394 coalesced_columns.add(name) 395 tables = using_column_tables[name] 396 coalesce = [exp.column(name, table=table) for table in tables] 397 398 new_selections.append( 399 alias( 400 exp.Coalesce(this=coalesce[0], expressions=coalesce[1:]), 401 alias=name, 402 copy=False, 403 ) 404 ) 405 elif name not in except_columns.get(table_id, set()): 406 alias_ = replace_columns.get(table_id, {}).get(name, name) 407 column = exp.column(name, table=table) 408 new_selections.append( 409 alias(column, alias_, copy=False) if alias_ != name else column 410 ) 411 else: 412 return 413 414 scope.expression.set("expressions", new_selections) 415 416 417def _add_except_columns( 418 expression: exp.Expression, tables, except_columns: t.Dict[int, t.Set[str]] 419) -> None: 420 except_ = expression.args.get("except") 421 422 if not except_: 423 return 424 425 columns = {e.name for e in except_} 426 427 for table in tables: 428 except_columns[id(table)] = columns 429 430 431def _add_replace_columns( 432 expression: exp.Expression, tables, replace_columns: t.Dict[int, t.Dict[str, str]] 433) -> None: 434 replace = expression.args.get("replace") 435 436 if not replace: 437 return 438 439 columns = {e.this.name: e.alias for e in replace} 440 441 for table in tables: 442 replace_columns[id(table)] = columns 443 444 445def _qualify_outputs(scope: Scope): 446 """Ensure all output columns are aliased""" 447 new_selections = [] 448 449 for i, (selection, aliased_column) in enumerate( 450 itertools.zip_longest(scope.selects, scope.outer_column_list) 451 ): 452 if isinstance(selection, exp.Subquery): 453 if not selection.output_name: 454 selection.set("alias", exp.TableAlias(this=exp.to_identifier(f"_col_{i}"))) 455 elif not isinstance(selection, exp.Alias) and not selection.is_star: 456 selection = alias( 457 selection, 458 alias=selection.output_name or f"_col_{i}", 459 ) 460 if aliased_column: 461 selection.set("alias", exp.to_identifier(aliased_column)) 462 463 new_selections.append(selection) 464 465 scope.expression.set("expressions", new_selections) 466 467 468def quote_identifiers(expression: E, dialect: DialectType = None, identify: bool = True) -> E: 469 """Makes sure all identifiers that need to be quoted are quoted.""" 470 return expression.transform( 471 Dialect.get_or_raise(dialect).quote_identifier, identify=identify, copy=False 472 ) 473 474 475class Resolver: 476 """ 477 Helper for resolving columns. 478 479 This is a class so we can lazily load some things and easily share them across functions. 480 """ 481 482 def __init__(self, scope: Scope, schema: Schema, infer_schema: bool = True): 483 self.scope = scope 484 self.schema = schema 485 self._source_columns = None 486 self._unambiguous_columns: t.Optional[t.Dict[str, str]] = None 487 self._all_columns = None 488 self._infer_schema = infer_schema 489 490 def get_table(self, column_name: str) -> t.Optional[exp.Identifier]: 491 """ 492 Get the table for a column name. 493 494 Args: 495 column_name: The column name to find the table for. 496 Returns: 497 The table name if it can be found/inferred. 498 """ 499 if self._unambiguous_columns is None: 500 self._unambiguous_columns = self._get_unambiguous_columns( 501 self._get_all_source_columns() 502 ) 503 504 table_name = self._unambiguous_columns.get(column_name) 505 506 if not table_name and self._infer_schema: 507 sources_without_schema = tuple( 508 source 509 for source, columns in self._get_all_source_columns().items() 510 if not columns or "*" in columns 511 ) 512 if len(sources_without_schema) == 1: 513 table_name = sources_without_schema[0] 514 515 if table_name not in self.scope.selected_sources: 516 return exp.to_identifier(table_name) 517 518 node, _ = self.scope.selected_sources.get(table_name) 519 520 if isinstance(node, exp.Subqueryable): 521 while node and node.alias != table_name: 522 node = node.parent 523 524 node_alias = node.args.get("alias") 525 if node_alias: 526 return exp.to_identifier(node_alias.this) 527 528 return exp.to_identifier(table_name) 529 530 @property 531 def all_columns(self): 532 """All available columns of all sources in this scope""" 533 if self._all_columns is None: 534 self._all_columns = { 535 column for columns in self._get_all_source_columns().values() for column in columns 536 } 537 return self._all_columns 538 539 def get_source_columns(self, name, only_visible=False): 540 """Resolve the source columns for a given source `name`""" 541 if name not in self.scope.sources: 542 raise OptimizeError(f"Unknown table: {name}") 543 544 source = self.scope.sources[name] 545 546 # If referencing a table, return the columns from the schema 547 if isinstance(source, exp.Table): 548 return self.schema.column_names(source, only_visible) 549 550 if isinstance(source, Scope) and isinstance(source.expression, exp.Values): 551 return source.expression.alias_column_names 552 553 # Otherwise, if referencing another scope, return that scope's named selects 554 return source.expression.named_selects 555 556 def _get_all_source_columns(self): 557 if self._source_columns is None: 558 self._source_columns = { 559 k: self.get_source_columns(k) 560 for k in itertools.chain(self.scope.selected_sources, self.scope.lateral_sources) 561 } 562 return self._source_columns 563 564 def _get_unambiguous_columns(self, source_columns): 565 """ 566 Find all the unambiguous columns in sources. 567 568 Args: 569 source_columns (dict): Mapping of names to source columns 570 Returns: 571 dict: Mapping of column name to source name 572 """ 573 if not source_columns: 574 return {} 575 576 source_columns = list(source_columns.items()) 577 578 first_table, first_columns = source_columns[0] 579 unambiguous_columns = {col: first_table for col in self._find_unique_columns(first_columns)} 580 all_columns = set(unambiguous_columns) 581 582 for table, columns in source_columns[1:]: 583 unique = self._find_unique_columns(columns) 584 ambiguous = set(all_columns).intersection(unique) 585 all_columns.update(columns) 586 for column in ambiguous: 587 unambiguous_columns.pop(column, None) 588 for column in unique.difference(ambiguous): 589 unambiguous_columns[column] = table 590 591 return unambiguous_columns 592 593 @staticmethod 594 def _find_unique_columns(columns): 595 """ 596 Find the unique columns in a list of columns. 597 598 Example: 599 >>> sorted(Resolver._find_unique_columns(["a", "b", "b", "c"])) 600 ['a', 'c'] 601 602 This is necessary because duplicate column names are ambiguous. 603 """ 604 counts = {} 605 for column in columns: 606 counts[column] = counts.get(column, 0) + 1 607 return {column for column, count in counts.items() if count == 1}
def
qualify_columns( expression: sqlglot.expressions.Expression, schema: Union[Dict, sqlglot.schema.Schema], expand_alias_refs: bool = True, infer_schema: Optional[bool] = None) -> sqlglot.expressions.Expression:
16def qualify_columns( 17 expression: exp.Expression, 18 schema: t.Dict | Schema, 19 expand_alias_refs: bool = True, 20 infer_schema: t.Optional[bool] = None, 21) -> exp.Expression: 22 """ 23 Rewrite sqlglot AST to have fully qualified columns. 24 25 Example: 26 >>> import sqlglot 27 >>> schema = {"tbl": {"col": "INT"}} 28 >>> expression = sqlglot.parse_one("SELECT col FROM tbl") 29 >>> qualify_columns(expression, schema).sql() 30 'SELECT tbl.col AS col FROM tbl' 31 32 Args: 33 expression: expression to qualify 34 schema: Database schema 35 expand_alias_refs: whether or not to expand references to aliases 36 infer_schema: whether or not to infer the schema if missing 37 Returns: 38 sqlglot.Expression: qualified expression 39 """ 40 schema = ensure_schema(schema) 41 infer_schema = schema.empty if infer_schema is None else infer_schema 42 43 for scope in traverse_scope(expression): 44 resolver = Resolver(scope, schema, infer_schema=infer_schema) 45 _pop_table_column_aliases(scope.ctes) 46 _pop_table_column_aliases(scope.derived_tables) 47 using_column_tables = _expand_using(scope, resolver) 48 49 if schema.empty and expand_alias_refs: 50 _expand_alias_refs(scope, resolver) 51 52 _qualify_columns(scope, resolver) 53 54 if not schema.empty and expand_alias_refs: 55 _expand_alias_refs(scope, resolver) 56 57 if not isinstance(scope.expression, exp.UDTF): 58 _expand_stars(scope, resolver, using_column_tables) 59 _qualify_outputs(scope) 60 _expand_group_by(scope) 61 _expand_order_by(scope, resolver) 62 63 return expression
Rewrite sqlglot AST to have fully qualified columns.
Example:
>>> import sqlglot >>> schema = {"tbl": {"col": "INT"}} >>> expression = sqlglot.parse_one("SELECT col FROM tbl") >>> qualify_columns(expression, schema).sql() 'SELECT tbl.col AS col FROM tbl'
Arguments:
- expression: expression to qualify
- schema: Database schema
- expand_alias_refs: whether or not to expand references to aliases
- infer_schema: whether or not to infer the schema if missing
Returns:
sqlglot.Expression: qualified expression
def
validate_qualify_columns(expression: ~E) -> ~E:
66def validate_qualify_columns(expression: E) -> E: 67 """Raise an `OptimizeError` if any columns aren't qualified""" 68 unqualified_columns = [] 69 for scope in traverse_scope(expression): 70 if isinstance(scope.expression, exp.Select): 71 unqualified_columns.extend(scope.unqualified_columns) 72 if scope.external_columns and not scope.is_correlated_subquery and not scope.pivots: 73 column = scope.external_columns[0] 74 raise OptimizeError( 75 f"""Column '{column}' could not be resolved{f" for table: '{column.table}'" if column.table else ''}""" 76 ) 77 78 if unqualified_columns: 79 raise OptimizeError(f"Ambiguous columns: {unqualified_columns}") 80 return expression
Raise an OptimizeError
if any columns aren't qualified
def
quote_identifiers( expression: ~E, dialect: Union[str, sqlglot.dialects.dialect.Dialect, Type[sqlglot.dialects.dialect.Dialect], NoneType] = None, identify: bool = True) -> ~E:
469def quote_identifiers(expression: E, dialect: DialectType = None, identify: bool = True) -> E: 470 """Makes sure all identifiers that need to be quoted are quoted.""" 471 return expression.transform( 472 Dialect.get_or_raise(dialect).quote_identifier, identify=identify, copy=False 473 )
Makes sure all identifiers that need to be quoted are quoted.
class
Resolver:
476class Resolver: 477 """ 478 Helper for resolving columns. 479 480 This is a class so we can lazily load some things and easily share them across functions. 481 """ 482 483 def __init__(self, scope: Scope, schema: Schema, infer_schema: bool = True): 484 self.scope = scope 485 self.schema = schema 486 self._source_columns = None 487 self._unambiguous_columns: t.Optional[t.Dict[str, str]] = None 488 self._all_columns = None 489 self._infer_schema = infer_schema 490 491 def get_table(self, column_name: str) -> t.Optional[exp.Identifier]: 492 """ 493 Get the table for a column name. 494 495 Args: 496 column_name: The column name to find the table for. 497 Returns: 498 The table name if it can be found/inferred. 499 """ 500 if self._unambiguous_columns is None: 501 self._unambiguous_columns = self._get_unambiguous_columns( 502 self._get_all_source_columns() 503 ) 504 505 table_name = self._unambiguous_columns.get(column_name) 506 507 if not table_name and self._infer_schema: 508 sources_without_schema = tuple( 509 source 510 for source, columns in self._get_all_source_columns().items() 511 if not columns or "*" in columns 512 ) 513 if len(sources_without_schema) == 1: 514 table_name = sources_without_schema[0] 515 516 if table_name not in self.scope.selected_sources: 517 return exp.to_identifier(table_name) 518 519 node, _ = self.scope.selected_sources.get(table_name) 520 521 if isinstance(node, exp.Subqueryable): 522 while node and node.alias != table_name: 523 node = node.parent 524 525 node_alias = node.args.get("alias") 526 if node_alias: 527 return exp.to_identifier(node_alias.this) 528 529 return exp.to_identifier(table_name) 530 531 @property 532 def all_columns(self): 533 """All available columns of all sources in this scope""" 534 if self._all_columns is None: 535 self._all_columns = { 536 column for columns in self._get_all_source_columns().values() for column in columns 537 } 538 return self._all_columns 539 540 def get_source_columns(self, name, only_visible=False): 541 """Resolve the source columns for a given source `name`""" 542 if name not in self.scope.sources: 543 raise OptimizeError(f"Unknown table: {name}") 544 545 source = self.scope.sources[name] 546 547 # If referencing a table, return the columns from the schema 548 if isinstance(source, exp.Table): 549 return self.schema.column_names(source, only_visible) 550 551 if isinstance(source, Scope) and isinstance(source.expression, exp.Values): 552 return source.expression.alias_column_names 553 554 # Otherwise, if referencing another scope, return that scope's named selects 555 return source.expression.named_selects 556 557 def _get_all_source_columns(self): 558 if self._source_columns is None: 559 self._source_columns = { 560 k: self.get_source_columns(k) 561 for k in itertools.chain(self.scope.selected_sources, self.scope.lateral_sources) 562 } 563 return self._source_columns 564 565 def _get_unambiguous_columns(self, source_columns): 566 """ 567 Find all the unambiguous columns in sources. 568 569 Args: 570 source_columns (dict): Mapping of names to source columns 571 Returns: 572 dict: Mapping of column name to source name 573 """ 574 if not source_columns: 575 return {} 576 577 source_columns = list(source_columns.items()) 578 579 first_table, first_columns = source_columns[0] 580 unambiguous_columns = {col: first_table for col in self._find_unique_columns(first_columns)} 581 all_columns = set(unambiguous_columns) 582 583 for table, columns in source_columns[1:]: 584 unique = self._find_unique_columns(columns) 585 ambiguous = set(all_columns).intersection(unique) 586 all_columns.update(columns) 587 for column in ambiguous: 588 unambiguous_columns.pop(column, None) 589 for column in unique.difference(ambiguous): 590 unambiguous_columns[column] = table 591 592 return unambiguous_columns 593 594 @staticmethod 595 def _find_unique_columns(columns): 596 """ 597 Find the unique columns in a list of columns. 598 599 Example: 600 >>> sorted(Resolver._find_unique_columns(["a", "b", "b", "c"])) 601 ['a', 'c'] 602 603 This is necessary because duplicate column names are ambiguous. 604 """ 605 counts = {} 606 for column in columns: 607 counts[column] = counts.get(column, 0) + 1 608 return {column for column, count in counts.items() if count == 1}
Helper for resolving columns.
This is a class so we can lazily load some things and easily share them across functions.
Resolver( scope: sqlglot.optimizer.scope.Scope, schema: sqlglot.schema.Schema, infer_schema: bool = True)
491 def get_table(self, column_name: str) -> t.Optional[exp.Identifier]: 492 """ 493 Get the table for a column name. 494 495 Args: 496 column_name: The column name to find the table for. 497 Returns: 498 The table name if it can be found/inferred. 499 """ 500 if self._unambiguous_columns is None: 501 self._unambiguous_columns = self._get_unambiguous_columns( 502 self._get_all_source_columns() 503 ) 504 505 table_name = self._unambiguous_columns.get(column_name) 506 507 if not table_name and self._infer_schema: 508 sources_without_schema = tuple( 509 source 510 for source, columns in self._get_all_source_columns().items() 511 if not columns or "*" in columns 512 ) 513 if len(sources_without_schema) == 1: 514 table_name = sources_without_schema[0] 515 516 if table_name not in self.scope.selected_sources: 517 return exp.to_identifier(table_name) 518 519 node, _ = self.scope.selected_sources.get(table_name) 520 521 if isinstance(node, exp.Subqueryable): 522 while node and node.alias != table_name: 523 node = node.parent 524 525 node_alias = node.args.get("alias") 526 if node_alias: 527 return exp.to_identifier(node_alias.this) 528 529 return exp.to_identifier(table_name)
Get the table for a column name.
Arguments:
- column_name: The column name to find the table for.
Returns:
The table name if it can be found/inferred.
def
get_source_columns(self, name, only_visible=False):
540 def get_source_columns(self, name, only_visible=False): 541 """Resolve the source columns for a given source `name`""" 542 if name not in self.scope.sources: 543 raise OptimizeError(f"Unknown table: {name}") 544 545 source = self.scope.sources[name] 546 547 # If referencing a table, return the columns from the schema 548 if isinstance(source, exp.Table): 549 return self.schema.column_names(source, only_visible) 550 551 if isinstance(source, Scope) and isinstance(source.expression, exp.Values): 552 return source.expression.alias_column_names 553 554 # Otherwise, if referencing another scope, return that scope's named selects 555 return source.expression.named_selects
Resolve the source columns for a given source name