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Commitd6f7d4f

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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 parent993ce4e commitd6f7d4f

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+32
-13
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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
@@ -209,7 +209,7 @@ static void get_rule_orderby(List *orderList, List *targetList,
209209
staticvoidget_rule_windowclause(Query*query,deparse_context*context);
210210
staticvoidget_rule_windowspec(WindowClause*wc,List*targetList,
211211
deparse_context*context);
212-
staticchar*get_variable(Var*var,intlevelsup,boolshowstar,
212+
staticchar*get_variable(Var*var,intlevelsup,boolistoplevel,
213213
deparse_context*context);
214214
staticRangeTblEntry*find_rte_by_refname(constchar*refname,
215215
deparse_context*context);
@@ -3074,11 +3074,12 @@ get_target_list(List *targetList, deparse_context *context,
30743074
* "foo.*", which is the preferred notation in most contexts, but at
30753075
* the top level of a SELECT list it's not right (the parser will
30763076
* expand that notation into multiple columns, yielding behavior
3077-
* different from a whole-row Var). We want just "foo", instead.
3077+
* different from a whole-row Var). We need to call get_variable
3078+
* directly so that we can tell it to do the right thing.
30783079
*/
30793080
if (tle->expr&&IsA(tle->expr,Var))
30803081
{
3081-
attname=get_variable((Var*)tle->expr,0,false,context);
3082+
attname=get_variable((Var*)tle->expr,0,true,context);
30823083
}
30833084
else
30843085
{
@@ -3803,13 +3804,20 @@ get_utility_query_def(Query *query, deparse_context *context)
38033804
* the Var's varlevelsup has to be interpreted with respect to a context
38043805
* above the current one; levelsup indicates the offset.
38053806
*
3806-
* If showstar is TRUE, whole-row Vars are displayed as "foo.*";
3807-
* if FALSE, merely as "foo".
3807+
* If istoplevel is TRUE, the Var is at the top level of a SELECT's
3808+
* targetlist, which means we need special treatment of whole-row Vars.
3809+
* Instead of the normal "tab.*", we'll print "tab.*::typename", which is a
3810+
* dirty hack to prevent "tab.*" from being expanded into multiple columns.
3811+
* (The parser will strip the useless coercion, so no inefficiency is added in
3812+
* dump and reload.) We used to print just "tab" in such cases, but that is
3813+
* ambiguous and will yield the wrong result if "tab" is also a plain column
3814+
* name in the query.
38083815
*
3809-
* Returns the attname of the Var, or NULL if not determinable.
3816+
* Returns the attname of the Var, or NULL if the Var has no attname (because
3817+
* it is a whole-row Var).
38103818
*/
38113819
staticchar*
3812-
get_variable(Var*var,intlevelsup,boolshowstar,deparse_context*context)
3820+
get_variable(Var*var,intlevelsup,boolistoplevel,deparse_context*context)
38133821
{
38143822
StringInfobuf=context->buf;
38153823
RangeTblEntry*rte;
@@ -3998,10 +4006,16 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
39984006
if (IsA(aliasvar,Var))
39994007
{
40004008
returnget_variable(aliasvar,var->varlevelsup+levelsup,
4001-
showstar,context);
4009+
istoplevel,context);
40024010
}
40034011
}
4004-
/* Unnamed join has neither schemaname nor refname */
4012+
4013+
/*
4014+
* Unnamed join has neither schemaname nor refname. (Note: since
4015+
* it's unnamed, there is no way the user could have referenced it
4016+
* to create a whole-row Var for it. So we don't have to cover
4017+
* that case below.)
4018+
*/
40054019
refname=NULL;
40064020
}
40074021
}
@@ -4017,13 +4031,18 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
40174031
appendStringInfo(buf,"%s.",
40184032
quote_identifier(schemaname));
40194033
appendStringInfoString(buf,quote_identifier(refname));
4020-
if (attname||showstar)
4021-
appendStringInfoChar(buf,'.');
4034+
appendStringInfoChar(buf,'.');
40224035
}
40234036
if (attname)
40244037
appendStringInfoString(buf,quote_identifier(attname));
4025-
elseif (showstar)
4038+
else
4039+
{
40264040
appendStringInfoChar(buf,'*');
4041+
if (istoplevel)
4042+
appendStringInfo(buf,"::%s",
4043+
format_type_with_typemod(var->vartype,
4044+
var->vartypmod));
4045+
}
40274046

40284047
returnattname;
40294048
}
@@ -4974,7 +4993,7 @@ get_rule_expr(Node *node, deparse_context *context,
49744993
switch (nodeTag(node))
49754994
{
49764995
caseT_Var:
4977-
(void)get_variable((Var*)node,0,true,context);
4996+
(void)get_variable((Var*)node,0,false,context);
49784997
break;
49794998

49804999
caseT_Const:

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