diff options
Diffstat (limited to 'src/backend/commands/tablecmds.c')
| -rw-r--r-- | src/backend/commands/tablecmds.c | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index f901ecfd27f..5789a39ba3d 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -6632,10 +6632,14 @@ ATPrepAlterColumnType(List **wqueue, } /* - * When the data type of a column is changed, a rewrite might not be require - * if the data type is being changed to its current type, or more interestingly - * to a type to which it is binary coercible. But we must check carefully that - * the USING clause isn't trying to insert some other value. + * When the data type of a column is changed, a rewrite might not be required + * if the new type is sufficiently identical to the old one, and the USING + * clause isn't trying to insert some other value. It's safe to skip the + * rewrite if the old type is binary coercible to the new type, or if the + * new type is an unconstrained domain over the old type. In the case of a + * constrained domain, we could get by with scanning the table and checking + * the constraint rather than actually rewriting it, but we don't currently + * try to do that. */ static bool ATColumnChangeRequiresRewrite(Node *expr, AttrNumber varattno) @@ -6649,6 +6653,14 @@ ATColumnChangeRequiresRewrite(Node *expr, AttrNumber varattno) return false; else if (IsA(expr, RelabelType)) expr = (Node *) ((RelabelType *) expr)->arg; + else if (IsA(expr, CoerceToDomain)) + { + CoerceToDomain *d = (CoerceToDomain *) expr; + + if (GetDomainConstraints(d->resulttype) != NIL) + return true; + expr = (Node *) d->arg; + } else return true; } |