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Create a new expression node type RelabelType, which exists solely to

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represent the result of a binary-compatible type coercion.  At runtime
it just evaluates its argument --- but during type resolution, exprType
will pick up the output type of the RelabelType node instead of the type
of the argument.  This solves some longstanding problems with dropped
type coercions, an example being 'select now()::abstime::int4' which
used to produce date-formatted output, not an integer, because the
coercion to int4 was dropped on the floor.
This commit is contained in:
Tom Lane
2000-02-20 21:32:16 +00:00
parent bd8e071482
commit 57b30e8e22
13 changed files with 325 additions and 86 deletions
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45
src/backend/optimizer/util/clauses.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.59 2000/02/15 03:37:36 thomas Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.60 2000/02/20 21:32:06 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@@ -1150,6 +1150,37 @@ eval_const_expressions_mutator (Node *node, void *context)
newexpr->args = args;
return (Node *) newexpr;
}
if (IsA(node, RelabelType))
{
/*
* If we can simplify the input to a constant, then we don't need
* the RelabelType node anymore: just change the type field of
* the Const node. Otherwise keep the RelabelType node.
*
* XXX if relabel has a nondefault resulttypmod, do we need to
* keep it to show that? At present I don't think so.
*/
RelabelType *relabel = (RelabelType *) node;
Node *arg;
arg = eval_const_expressions_mutator(relabel->arg, context);
if (arg && IsA(arg, Const))
{
Const *con = (Const *) arg;
con->consttype = relabel->resulttype;
return (Node *) con;
}
else
{
RelabelType *newrelabel = makeNode(RelabelType);
newrelabel->arg = arg;
newrelabel->resulttype = relabel->resulttype;
newrelabel->resulttypmod = relabel->resulttypmod;
return (Node *) newrelabel;
}
}
if (IsA(node, CaseExpr))
{
/*
@@ -1392,6 +1423,8 @@ expression_tree_walker(Node *node, bool (*walker) (), void *context)
return true;
}
break;
case T_RelabelType:
return walker(((RelabelType *) node)->arg, context);
case T_CaseExpr:
{
CaseExpr *caseexpr = (CaseExpr *) node;
@@ -1603,6 +1636,16 @@ expression_tree_mutator(Node *node, Node * (*mutator) (), void *context)
return (Node *) newnode;
}
break;
case T_RelabelType:
{
RelabelType *relabel = (RelabelType *) node;
RelabelType *newnode;
FLATCOPY(newnode, relabel, RelabelType);
MUTATE(newnode->arg, relabel->arg, Node *);
return (Node *) newnode;
}
break;
case T_CaseExpr:
{
CaseExpr *caseexpr = (CaseExpr *) node;