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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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32
src/backend/parser/parse_coerce.c
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@ -1,14 +1,14 @@
/*-------------------------------------------------------------------------
*
* parse_coerce.c
* handle type coersions/conversions for parser
* handle type coercions/conversions for parser
*
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/parse_coerce.c,v 2.31 2000/02/20 06:28:42 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/parse_coerce.c,v 2.32 2000/02/20 21:32:09 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -36,7 +36,7 @@ Node *
coerce_type(ParseState *pstate, Node *node, Oid inputTypeId,
Oid targetTypeId, int32 atttypmod)
{
Node *result = NULL;
Node *result;
if (targetTypeId == InvalidOid ||
targetTypeId == inputTypeId)
@ -44,11 +44,6 @@ coerce_type(ParseState *pstate, Node *node, Oid inputTypeId,
/* no conversion needed */
result = node;
}
else if (IS_BINARY_COMPATIBLE(inputTypeId, targetTypeId))
{
/* no work if one of the known-good transparent conversions */
result = node;
}
else if (inputTypeId == UNKNOWNOID && IsA(node, Const))
{
/*
@ -87,6 +82,27 @@ coerce_type(ParseState *pstate, Node *node, Oid inputTypeId,
result = (Node *) newcon;
}
else if (IS_BINARY_COMPATIBLE(inputTypeId, targetTypeId))
{
/*
* We don't really need to do a conversion, but we do need to attach
* a RelabelType node so that the expression will be seen to have
* the intended type when inspected by higher-level code.
*/
RelabelType *relabel = makeNode(RelabelType);
relabel->arg = node;
relabel->resulttype = targetTypeId;
/*
* XXX could we label result with exprTypmod(node) instead of
* default -1 typmod, to save a possible length-coercion later?
* Would work if both types have same interpretation of typmod,
* which is likely but not certain.
*/
relabel->resulttypmod = -1;
result = (Node *) relabel;
}
else
{
/*