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Commit14f9fb5

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Fix printing of whole-row Vars at top level of a SELECT targetlist.
Normally whole-row Vars are printed as "tabname.*". However, that does notwork at top level of a targetlist, because per SQL standard the parser willthink that the "*" should result in column-by-column expansion; which isnot at all what a whole-row Var implies. We used to just print the tablename in such cases, which works most of the time; but it fails if the tablename matches a column name available anywhere in the FROM clause. Thiscould lead for instance to a view being interpreted differently after dumpand reload. Adding parentheses doesn't fix it, but there is a reasonablysimple kluge we can use instead: attach a no-op cast, so that the "*" isn'tsyntactically at top level anymore. This makes the printing of suchwhole-row Vars a lot more consistent with other Vars, and may indeed fixmore cases than just the reported one; I'm suspicious that cases involvingschema qualification probably didn't work properly before, either.Per bug report and fix proposal from Abbas Butt, though this patch is quitedifferent in detail from his.Back-patch to all supported versions.
1 parenta6708e2 commit14f9fb5

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1 file changed

+32
-13
lines changed

1 file changed

+32
-13
lines changed

‎src/backend/utils/adt/ruleutils.c‎

Lines changed: 32 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -184,7 +184,7 @@ static void get_rule_windowclause(Query *query, deparse_context *context);
184184
staticvoidget_rule_windowspec(WindowClause*wc,List*targetList,
185185
deparse_context*context);
186186
staticvoidpush_plan(deparse_namespace*dpns,Plan*subplan);
187-
staticchar*get_variable(Var*var,intlevelsup,boolshowstar,
187+
staticchar*get_variable(Var*var,intlevelsup,boolistoplevel,
188188
deparse_context*context);
189189
staticRangeTblEntry*find_rte_by_refname(constchar*refname,
190190
deparse_context*context);
@@ -2822,11 +2822,12 @@ get_target_list(List *targetList, deparse_context *context,
28222822
* "foo.*", which is the preferred notation in most contexts, but at
28232823
* the top level of a SELECT list it's not right (the parser will
28242824
* expand that notation into multiple columns, yielding behavior
2825-
* different from a whole-row Var). We want just "foo", instead.
2825+
* different from a whole-row Var). We need to call get_variable
2826+
* directly so that we can tell it to do the right thing.
28262827
*/
28272828
if (tle->expr&&IsA(tle->expr,Var))
28282829
{
2829-
attname=get_variable((Var*)tle->expr,0,false,context);
2830+
attname=get_variable((Var*)tle->expr,0,true,context);
28302831
}
28312832
else
28322833
{
@@ -3539,13 +3540,20 @@ push_plan(deparse_namespace *dpns, Plan *subplan)
35393540
* the Var's varlevelsup has to be interpreted with respect to a context
35403541
* above the current one; levelsup indicates the offset.
35413542
*
3542-
* If showstar is TRUE, whole-row Vars are displayed as "foo.*";
3543-
* if FALSE, merely as "foo".
3543+
* If istoplevel is TRUE, the Var is at the top level of a SELECT's
3544+
* targetlist, which means we need special treatment of whole-row Vars.
3545+
* Instead of the normal "tab.*", we'll print "tab.*::typename", which is a
3546+
* dirty hack to prevent "tab.*" from being expanded into multiple columns.
3547+
* (The parser will strip the useless coercion, so no inefficiency is added in
3548+
* dump and reload.) We used to print just "tab" in such cases, but that is
3549+
* ambiguous and will yield the wrong result if "tab" is also a plain column
3550+
* name in the query.
35443551
*
3545-
* Returns the attname of the Var, or NULL if not determinable.
3552+
* Returns the attname of the Var, or NULL if the Var has no attname (because
3553+
* it is a whole-row Var).
35463554
*/
35473555
staticchar*
3548-
get_variable(Var*var,intlevelsup,boolshowstar,deparse_context*context)
3556+
get_variable(Var*var,intlevelsup,boolistoplevel,deparse_context*context)
35493557
{
35503558
StringInfobuf=context->buf;
35513559
RangeTblEntry*rte;
@@ -3724,10 +3732,16 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
37243732
if (IsA(aliasvar,Var))
37253733
{
37263734
returnget_variable(aliasvar,var->varlevelsup+levelsup,
3727-
showstar,context);
3735+
istoplevel,context);
37283736
}
37293737
}
3730-
/* Unnamed join has neither schemaname nor refname */
3738+
3739+
/*
3740+
* Unnamed join has neither schemaname nor refname. (Note: since
3741+
* it's unnamed, there is no way the user could have referenced it
3742+
* to create a whole-row Var for it. So we don't have to cover
3743+
* that case below.)
3744+
*/
37313745
refname=NULL;
37323746
}
37333747
}
@@ -3743,13 +3757,18 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
37433757
appendStringInfo(buf,"%s.",
37443758
quote_identifier(schemaname));
37453759
appendStringInfoString(buf,quote_identifier(refname));
3746-
if (attname||showstar)
3747-
appendStringInfoChar(buf,'.');
3760+
appendStringInfoChar(buf,'.');
37483761
}
37493762
if (attname)
37503763
appendStringInfoString(buf,quote_identifier(attname));
3751-
elseif (showstar)
3764+
else
3765+
{
37523766
appendStringInfoChar(buf,'*');
3767+
if (istoplevel)
3768+
appendStringInfo(buf,"::%s",
3769+
format_type_with_typemod(var->vartype,
3770+
var->vartypmod));
3771+
}
37533772

37543773
returnattname;
37553774
}
@@ -4489,7 +4508,7 @@ get_rule_expr(Node *node, deparse_context *context,
44894508
switch (nodeTag(node))
44904509
{
44914510
caseT_Var:
4492-
(void)get_variable((Var*)node,0,true,context);
4511+
(void)get_variable((Var*)node,0,false,context);
44934512
break;
44944513

44954514
caseT_Const:

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