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Clean up handling of explicit NULL constants. Cases like

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SELECT null::text;
	SELECT int4fac(null);
work as expected now.  In some cases a NULL must be surrounded by
parentheses:
	SELECT 2 + null;                 fails
	SELECT 2 + (null);               OK
This is a grammatical ambiguity that seems difficult to avoid.  Other
than that, NULLs seem to behave about like you'd expect.  The internal
implementation is that NULL constants are typed as UNKNOWN (like
untyped string constants) until the parser can deduce the right type.
This commit is contained in:
Tom Lane
1999-12-24 06:43:34 +00:00
parent bd5ea42a8d
commit 350cb386af
4 changed files with 67 additions and 43 deletions
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21
src/backend/utils/adt/ruleutils.c
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@ -3,7 +3,7 @@
* out of it's tuple
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.35 1999/12/13 01:27:01 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/ruleutils.c,v 1.36 1999/12/24 06:43:34 tgl Exp $
*
* This software is copyrighted by Jan Wieck - Hamburg.
*
@ -1606,12 +1606,6 @@ get_const_expr(Const *constval, deparse_context *context)
char *valptr;
bool isnull = FALSE;
if (constval->constisnull)
{
appendStringInfo(buf, "NULL");
return;
}
typetup = SearchSysCacheTuple(TYPEOID,
ObjectIdGetDatum(constval->consttype),
0, 0, 0);
@ -1620,6 +1614,19 @@ get_const_expr(Const *constval, deparse_context *context)
typeStruct = (Form_pg_type) GETSTRUCT(typetup);
if (constval->constisnull)
{
/*
* Always label the type of a NULL constant. This not only
* prevents misdecisions about the type, but it ensures that
* our output is a valid b_expr.
*/
extval = pstrdup(NameStr(typeStruct->typname));
appendStringInfo(buf, "NULL::%s", quote_identifier(extval));
pfree(extval);
return;
}
fmgr_info(typeStruct->typoutput, &finfo_output);
extval = (char *) (*fmgr_faddr(&finfo_output)) (constval->constvalue,
&isnull, -1);