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In ALTER COLUMN TYPE, strip any implicit coercion operations appearing

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at the top level of the column's old default expression before adding
an implicit coercion to the new column type.  This seems to satisfy the
principle of least surprise, as per discussion of bug #1290.
This commit is contained in:
Tom Lane
2004-10-22 17:20:05 +00:00
parent 4733dcc592
commit 9309d5f2ba
4 changed files with 65 additions and 5 deletions
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37
src/backend/optimizer/util/clauses.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.182 2004/10/07 18:38:49 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.183 2004/10/22 17:20:05 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@@ -1021,6 +1021,41 @@ CommuteClause(OpExpr *clause)
lsecond(clause->args) = temp;
}
/*
* strip_implicit_coercions: remove implicit coercions at top level of tree
*
* Note: there isn't any useful thing we can do with a RowExpr here, so
* just return it unchanged, even if it's marked as an implicit coercion.
*/
Node *
strip_implicit_coercions(Node *node)
{
if (node == NULL)
return NULL;
if (IsA(node, FuncExpr))
{
FuncExpr *f = (FuncExpr *) node;
if (f->funcformat == COERCE_IMPLICIT_CAST)
return strip_implicit_coercions(linitial(f->args));
}
else if (IsA(node, RelabelType))
{
RelabelType *r = (RelabelType *) node;
if (r->relabelformat == COERCE_IMPLICIT_CAST)
return strip_implicit_coercions((Node *) r->arg);
}
else if (IsA(node, CoerceToDomain))
{
CoerceToDomain *c = (CoerceToDomain *) node;
if (c->coercionformat == COERCE_IMPLICIT_CAST)
return strip_implicit_coercions((Node *) c->arg);
}
return node;
}
/*
* set_coercionform_dontcare: set all CoercionForm fields to COERCE_DONTCARE
*