diff options
Diffstat (limited to 'sqlglot/optimizer/qualify_tables.py')
| -rw-r--r-- | sqlglot/optimizer/qualify_tables.py | 37 |
1 files changed, 13 insertions, 24 deletions
diff --git a/sqlglot/optimizer/qualify_tables.py b/sqlglot/optimizer/qualify_tables.py index af8c716..31c9cc0 100644 --- a/sqlglot/optimizer/qualify_tables.py +++ b/sqlglot/optimizer/qualify_tables.py @@ -15,7 +15,8 @@ def qualify_tables( schema: t.Optional[Schema] = None, ) -> E: """ - Rewrite sqlglot AST to have fully qualified, unnested tables. + Rewrite sqlglot AST to have fully qualified tables. Join constructs such as + (t1 JOIN t2) AS t will be expanded into (SELECT * FROM t1 AS t1, t2 AS t2) AS t. Examples: >>> import sqlglot @@ -23,18 +24,9 @@ def qualify_tables( >>> qualify_tables(expression, db="db").sql() 'SELECT 1 FROM db.tbl AS tbl' >>> - >>> expression = sqlglot.parse_one("SELECT * FROM (tbl)") + >>> expression = sqlglot.parse_one("SELECT 1 FROM (t1 JOIN t2) AS t") >>> qualify_tables(expression).sql() - 'SELECT * FROM tbl AS tbl' - >>> - >>> expression = sqlglot.parse_one("SELECT * FROM (tbl1 JOIN tbl2 ON id1 = id2)") - >>> qualify_tables(expression).sql() - 'SELECT * FROM tbl1 AS tbl1 JOIN tbl2 AS tbl2 ON id1 = id2' - - Note: - This rule effectively enforces a left-to-right join order, since all joins - are unnested. This means that the optimizer doesn't necessarily preserve the - original join order, e.g. when parentheses are used to specify it explicitly. + 'SELECT 1 FROM (SELECT * FROM t1 AS t1, t2 AS t2) AS t' Args: expression: Expression to qualify @@ -49,6 +41,13 @@ def qualify_tables( for scope in traverse_scope(expression): for derived_table in itertools.chain(scope.ctes, scope.derived_tables): + if isinstance(derived_table, exp.Subquery): + unnested = derived_table.unnest() + if isinstance(unnested, exp.Table): + joins = unnested.args.pop("joins", None) + derived_table.this.replace(exp.select("*").from_(unnested.copy(), copy=False)) + derived_table.this.set("joins", joins) + if not derived_table.args.get("alias"): alias_ = next_alias_name() derived_table.set("alias", exp.TableAlias(this=exp.to_identifier(alias_))) @@ -66,19 +65,9 @@ def qualify_tables( if not source.args.get("catalog"): source.set("catalog", exp.to_identifier(catalog)) - # Unnest joins attached in tables by appending them to the closest query - for join in source.args.get("joins") or []: - scope.expression.append("joins", join) - - source.set("joins", None) - source.set("wrapped", None) - if not source.alias: - source = source.replace( - alias( - source, name or source.name or next_alias_name(), copy=True, table=True - ) - ) + # Mutates the source by attaching an alias to it + alias(source, name or source.name or next_alias_name(), copy=False, table=True) pivots = source.args.get("pivots") if pivots and not pivots[0].alias: |