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Expand virtual generated columns for ALTER COLUMN TYPE

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For the subcommand ALTER COLUMN TYPE of the ALTER TABLE command, the
USING expression may reference virtual generated columns.  These
columns must be expanded before the expression is fed through
expression_planner and the expression-execution machinery.  Failing to
do so can result in incorrect rewrite decisions, and can also lead to
"ERROR:  unexpected virtual generated column reference".

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: jian he <jian.universality@gmail.com>
Discussion: https://postgr.es/m/b5f96b24-ccac-47fd-9e20-14681b894f36@gmail.com
This commit is contained in:
Richard Guo
2025-06-26 12:17:12 +09:00
parent 62a47aea1d
commit 5069fef1cf
3 changed files with 30 additions and 19 deletions
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3
src/backend/commands/tablecmds.c
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@ -14484,6 +14484,9 @@ ATPrepAlterColumnType(List **wqueue,
/* Fix collations after all else */
assign_expr_collations(pstate, transform);
/* Expand virtual generated columns in the expr. */
transform = expand_generated_columns_in_expr(transform, rel, 1);
/* Plan the expr now so we can accurately assess the need to rewrite. */
transform = (Node *) expression_planner((Expr *) transform);