100 lines
4.1 KiB
Python
100 lines
4.1 KiB
Python
import itertools
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import typing as t
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from sqlglot import alias, exp
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from sqlglot._typing import E
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from sqlglot.helper import csv_reader, name_sequence
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from sqlglot.optimizer.scope import Scope, traverse_scope
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from sqlglot.schema import Schema
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def qualify_tables(
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expression: E,
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db: t.Optional[str] = None,
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catalog: t.Optional[str] = None,
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schema: t.Optional[Schema] = None,
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) -> E:
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"""
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Rewrite sqlglot AST to have fully qualified tables. Join constructs such as
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(t1 JOIN t2) AS t will be expanded into (SELECT * FROM t1 AS t1, t2 AS t2) AS t.
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Examples:
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>>> import sqlglot
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>>> expression = sqlglot.parse_one("SELECT 1 FROM tbl")
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>>> qualify_tables(expression, db="db").sql()
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'SELECT 1 FROM db.tbl AS tbl'
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>>>
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>>> expression = sqlglot.parse_one("SELECT 1 FROM (t1 JOIN t2) AS t")
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>>> qualify_tables(expression).sql()
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'SELECT 1 FROM (SELECT * FROM t1 AS t1, t2 AS t2) AS t'
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Args:
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expression: Expression to qualify
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db: Database name
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catalog: Catalog name
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schema: A schema to populate
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Returns:
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The qualified expression.
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"""
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next_alias_name = name_sequence("_q_")
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for scope in traverse_scope(expression):
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for derived_table in itertools.chain(scope.ctes, scope.derived_tables):
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if isinstance(derived_table, exp.Subquery):
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unnested = derived_table.unnest()
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if isinstance(unnested, exp.Table):
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joins = unnested.args.pop("joins", None)
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derived_table.this.replace(exp.select("*").from_(unnested.copy(), copy=False))
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derived_table.this.set("joins", joins)
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if not derived_table.args.get("alias"):
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alias_ = next_alias_name()
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derived_table.set("alias", exp.TableAlias(this=exp.to_identifier(alias_)))
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scope.rename_source(None, alias_)
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pivots = derived_table.args.get("pivots")
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if pivots and not pivots[0].alias:
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pivots[0].set("alias", exp.TableAlias(this=exp.to_identifier(next_alias_name())))
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for name, source in scope.sources.items():
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if isinstance(source, exp.Table):
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if isinstance(source.this, exp.Identifier):
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if not source.args.get("db"):
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source.set("db", exp.to_identifier(db))
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if not source.args.get("catalog"):
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source.set("catalog", exp.to_identifier(catalog))
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if not source.alias:
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# Mutates the source by attaching an alias to it
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alias(source, name or source.name or next_alias_name(), copy=False, table=True)
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pivots = source.args.get("pivots")
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if pivots and not pivots[0].alias:
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pivots[0].set(
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"alias", exp.TableAlias(this=exp.to_identifier(next_alias_name()))
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)
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if schema and isinstance(source.this, exp.ReadCSV):
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with csv_reader(source.this) as reader:
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header = next(reader)
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columns = next(reader)
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schema.add_table(
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source,
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{k: type(v).__name__ for k, v in zip(header, columns)},
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match_depth=False,
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)
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elif isinstance(source, Scope) and source.is_udtf:
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udtf = source.expression
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table_alias = udtf.args.get("alias") or exp.TableAlias(
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this=exp.to_identifier(next_alias_name())
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)
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udtf.set("alias", table_alias)
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if not table_alias.name:
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table_alias.set("this", exp.to_identifier(next_alias_name()))
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if isinstance(udtf, exp.Values) and not table_alias.columns:
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for i, e in enumerate(udtf.expressions[0].expressions):
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table_alias.append("columns", exp.to_identifier(f"_col_{i}"))
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return expression
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