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Commit08bc189

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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 parent1869f00 commit08bc189

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+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
@@ -203,7 +203,7 @@ static void get_rule_orderby(List *orderList, List *targetList,
203203
staticvoidget_rule_windowclause(Query*query,deparse_context*context);
204204
staticvoidget_rule_windowspec(WindowClause*wc,List*targetList,
205205
deparse_context*context);
206-
staticchar*get_variable(Var*var,intlevelsup,boolshowstar,
206+
staticchar*get_variable(Var*var,intlevelsup,boolistoplevel,
207207
deparse_context*context);
208208
staticRangeTblEntry*find_rte_by_refname(constchar*refname,
209209
deparse_context*context);
@@ -3013,11 +3013,12 @@ get_target_list(List *targetList, deparse_context *context,
30133013
* "foo.*", which is the preferred notation in most contexts, but at
30143014
* the top level of a SELECT list it's not right (the parser will
30153015
* expand that notation into multiple columns, yielding behavior
3016-
* different from a whole-row Var). We want just "foo", instead.
3016+
* different from a whole-row Var). We need to call get_variable
3017+
* directly so that we can tell it to do the right thing.
30173018
*/
30183019
if (tle->expr&&IsA(tle->expr,Var))
30193020
{
3020-
attname=get_variable((Var*)tle->expr,0,false,context);
3021+
attname=get_variable((Var*)tle->expr,0,true,context);
30213022
}
30223023
else
30233024
{
@@ -3684,13 +3685,20 @@ get_utility_query_def(Query *query, deparse_context *context)
36843685
* the Var's varlevelsup has to be interpreted with respect to a context
36853686
* above the current one; levelsup indicates the offset.
36863687
*
3687-
* If showstar is TRUE, whole-row Vars are displayed as "foo.*";
3688-
* if FALSE, merely as "foo".
3688+
* If istoplevel is TRUE, the Var is at the top level of a SELECT's
3689+
* targetlist, which means we need special treatment of whole-row Vars.
3690+
* Instead of the normal "tab.*", we'll print "tab.*::typename", which is a
3691+
* dirty hack to prevent "tab.*" from being expanded into multiple columns.
3692+
* (The parser will strip the useless coercion, so no inefficiency is added in
3693+
* dump and reload.) We used to print just "tab" in such cases, but that is
3694+
* ambiguous and will yield the wrong result if "tab" is also a plain column
3695+
* name in the query.
36893696
*
3690-
* Returns the attname of the Var, or NULL if not determinable.
3697+
* Returns the attname of the Var, or NULL if the Var has no attname (because
3698+
* it is a whole-row Var).
36913699
*/
36923700
staticchar*
3693-
get_variable(Var*var,intlevelsup,boolshowstar,deparse_context*context)
3701+
get_variable(Var*var,intlevelsup,boolistoplevel,deparse_context*context)
36943702
{
36953703
StringInfobuf=context->buf;
36963704
RangeTblEntry*rte;
@@ -3857,10 +3865,16 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
38573865
if (IsA(aliasvar,Var))
38583866
{
38593867
returnget_variable(aliasvar,var->varlevelsup+levelsup,
3860-
showstar,context);
3868+
istoplevel,context);
38613869
}
38623870
}
3863-
/* Unnamed join has neither schemaname nor refname */
3871+
3872+
/*
3873+
* Unnamed join has neither schemaname nor refname. (Note: since
3874+
* it's unnamed, there is no way the user could have referenced it
3875+
* to create a whole-row Var for it. So we don't have to cover
3876+
* that case below.)
3877+
*/
38643878
refname=NULL;
38653879
}
38663880
}
@@ -3876,13 +3890,18 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
38763890
appendStringInfo(buf,"%s.",
38773891
quote_identifier(schemaname));
38783892
appendStringInfoString(buf,quote_identifier(refname));
3879-
if (attname||showstar)
3880-
appendStringInfoChar(buf,'.');
3893+
appendStringInfoChar(buf,'.');
38813894
}
38823895
if (attname)
38833896
appendStringInfoString(buf,quote_identifier(attname));
3884-
elseif (showstar)
3897+
else
3898+
{
38853899
appendStringInfoChar(buf,'*');
3900+
if (istoplevel)
3901+
appendStringInfo(buf,"::%s",
3902+
format_type_with_typemod(var->vartype,
3903+
var->vartypmod));
3904+
}
38863905

38873906
returnattname;
38883907
}
@@ -4819,7 +4838,7 @@ get_rule_expr(Node *node, deparse_context *context,
48194838
switch (nodeTag(node))
48204839
{
48214840
caseT_Var:
4822-
(void)get_variable((Var*)node,0,true,context);
4841+
(void)get_variable((Var*)node,0,false,context);
48234842
break;
48244843

48254844
caseT_Const:

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