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Fix ALTER TABLE ADD VIRTUAL GENERATED COLUMN when table rewrite

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demo:
CREATE TABLE gtest20a (a int PRIMARY KEY, b int GENERATED ALWAYS AS (a * 2) VIRTUAL);
ALTER TABLE gtest20a ADD COLUMN c float8 DEFAULT RANDOM() CHECK (b < 60);
ERROR:  no generation expression found for column number 2 of table "pg_temp_17306"

In ATRewriteTable, the variable OIDNewHeap (if valid) corresponding
pg_attrdef default expression entry was not populated.  So OIDNewHeap
cannot be used to call expand_generated_columns_in_expr or
build_generation_expression.  Therefore in ATRewriteTable, we can only
use the existing relation to expand the generated expression.

Author: jian he <jian.universality@gmail.com>
Reviewed-by: Srinath Reddy <srinath2133@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CACJufxEJ%3DFoajabWXjszo_yrQeKSxdZ87KJqBW373rSbajKGAA%40mail.gmail.com
This commit is contained in:
Peter Eisentraut
2025-03-04 09:18:32 +01:00
parent 716a051aac
commit f011acdd61
5 changed files with 15 additions and 1 deletions
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2
src/backend/commands/tablecmds.c
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@ -6137,7 +6137,7 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
{
case CONSTR_CHECK:
needscan = true;
con->qualstate = ExecPrepareExpr((Expr *) expand_generated_columns_in_expr(con->qual, newrel ? newrel : oldrel, 1), estate);
con->qualstate = ExecPrepareExpr((Expr *) expand_generated_columns_in_expr(con->qual, oldrel, 1), estate);
break;
case CONSTR_FOREIGN:
/* Nothing to do here */