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Commit4227697

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Fix handling of opclauses in extended statistics
We expect opclauses to have exactly one Var and one Const, but the codewas checking the Const by calling is_pseudo_constant_clause() which isincorrect - we need a proper constant.Fixed by using plain IsA(x,Const) to check type of the node. We need todo these checks in two places, so move it into a separate function thatcan be called in both places.Reported by Andreas Seltenreich, based on crash reported by sqlsmith.Backpatch to v12, where this code was introduced.Discussion:https://postgr.es/m/8736jdhbhc.fsf%40ansel.ydns.euBackpatch-to: 12
1 parent3944e85 commit4227697

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3 files changed

+73
-32
lines changed

3 files changed

+73
-32
lines changed

‎src/backend/statistics/extended_stats.c‎

Lines changed: 64 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -796,21 +796,13 @@ statext_is_compatible_clause_internal(PlannerInfo *root, Node *clause,
796796
RangeTblEntry*rte=root->simple_rte_array[relid];
797797
OpExpr*expr= (OpExpr*)clause;
798798
Var*var;
799-
boolvaronleft= true;
800-
boolok;
801799

802800
/* Only expressions with two arguments are considered compatible. */
803801
if (list_length(expr->args)!=2)
804802
return false;
805803

806-
/* see if it actually has the right shape (one Var, one Const) */
807-
ok= (NumRelids((Node*)expr)==1)&&
808-
(is_pseudo_constant_clause(lsecond(expr->args))||
809-
(varonleft= false,
810-
is_pseudo_constant_clause(linitial(expr->args))));
811-
812-
/* unsupported structure (two variables or so) */
813-
if (!ok)
804+
/* Check if the expression the right shape (one Var, one Const) */
805+
if (!examine_opclause_expression(expr,&var,NULL,NULL))
814806
return false;
815807

816808
/*
@@ -850,8 +842,6 @@ statext_is_compatible_clause_internal(PlannerInfo *root, Node *clause,
850842
!get_func_leakproof(get_opcode(expr->opno)))
851843
return false;
852844

853-
var= (varonleft) ?linitial(expr->args) :lsecond(expr->args);
854-
855845
returnstatext_is_compatible_clause_internal(root, (Node*)var,
856846
relid,attnums);
857847
}
@@ -1196,3 +1186,65 @@ statext_clauselist_selectivity(PlannerInfo *root, List *clauses, int varRelid,
11961186

11971187
returnsel;
11981188
}
1189+
1190+
/*
1191+
* examine_operator_expression
1192+
*Split expression into Var and Const parts.
1193+
*
1194+
* Attempts to match the arguments to either (Var op Const) or (Const op Var),
1195+
* possibly with a RelabelType on top. When the expression matches this form,
1196+
* returns true, otherwise returns false.
1197+
*
1198+
* Optionally returns pointers to the extracted Var/Const nodes, when passed
1199+
* non-null pointers (varp, cstp and isgtp). The isgt flag specifies whether
1200+
* the Var node is on the left (false) or right (true) side of the operator.
1201+
*/
1202+
bool
1203+
examine_opclause_expression(OpExpr*expr,Var**varp,Const**cstp,bool*isgtp)
1204+
{
1205+
Var*var;
1206+
Const*cst;
1207+
boolisgt;
1208+
Node*leftop,
1209+
*rightop;
1210+
1211+
/* enforced by statext_is_compatible_clause_internal */
1212+
Assert(list_length(expr->args)==2);
1213+
1214+
leftop=linitial(expr->args);
1215+
rightop=lsecond(expr->args);
1216+
1217+
/* strip RelabelType from either side of the expression */
1218+
if (IsA(leftop,RelabelType))
1219+
leftop= (Node*) ((RelabelType*)leftop)->arg;
1220+
1221+
if (IsA(rightop,RelabelType))
1222+
rightop= (Node*) ((RelabelType*)rightop)->arg;
1223+
1224+
if (IsA(leftop,Var)&&IsA(rightop,Const))
1225+
{
1226+
var= (Var*)leftop;
1227+
cst= (Const*)rightop;
1228+
isgt= false;
1229+
}
1230+
elseif (IsA(leftop,Const)&&IsA(rightop,Var))
1231+
{
1232+
var= (Var*)rightop;
1233+
cst= (Const*)leftop;
1234+
isgt= true;
1235+
}
1236+
else
1237+
return false;
1238+
1239+
/* return pointers to the extracted parts if requested */
1240+
if (varp)
1241+
*varp=var;
1242+
1243+
if (cstp)
1244+
*cstp=cst;
1245+
1246+
if (isgtp)
1247+
*isgtp=isgt;
1248+
1249+
return true;
1250+
}

‎src/backend/statistics/mcv.c‎

Lines changed: 7 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -1561,36 +1561,23 @@ mcv_get_match_bitmap(PlannerInfo *root, List *clauses,
15611561
if (is_opclause(clause))
15621562
{
15631563
OpExpr*expr= (OpExpr*)clause;
1564-
boolvaronleft= true;
1565-
boolok;
15661564
FmgrInfoopproc;
15671565

15681566
/* get procedure computing operator selectivity */
15691567
RegProcedureoprrest=get_oprrest(expr->opno);
15701568

1571-
fmgr_info(get_opcode(expr->opno),&opproc);
1569+
/* valid only after examine_opclause_expression returns true */
1570+
Var*var;
1571+
Const*cst;
1572+
boolisgt;
15721573

1573-
ok= (NumRelids(clause)==1)&&
1574-
(is_pseudo_constant_clause(lsecond(expr->args))||
1575-
(varonleft= false,
1576-
is_pseudo_constant_clause(linitial(expr->args))));
1574+
fmgr_info(get_opcode(expr->opno),&opproc);
15771575

1578-
if (ok)
1576+
/* extract the var and const from the expression */
1577+
if (examine_opclause_expression(expr,&var,&cst,&isgt))
15791578
{
1580-
Var*var;
1581-
Const*cst;
1582-
boolisgt;
15831579
intidx;
15841580

1585-
/* extract the var and const from the expression */
1586-
var= (varonleft) ?linitial(expr->args) :lsecond(expr->args);
1587-
cst= (varonleft) ?lsecond(expr->args) :linitial(expr->args);
1588-
isgt= (!varonleft);
1589-
1590-
/* strip binary-compatible relabeling */
1591-
if (IsA(var,RelabelType))
1592-
var= (Var*) ((RelabelType*)var)->arg;
1593-
15941581
/* match the attribute to a dimension of the statistic */
15951582
idx=bms_member_index(keys,var->varattno);
15961583

‎src/include/statistics/extended_stats_internal.h‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -97,6 +97,8 @@ extern SortItem *build_sorted_items(int numrows, int *nitems, HeapTuple *rows,
9797
TupleDesctdesc,MultiSortSupportmss,
9898
intnumattrs,AttrNumber*attnums);
9999

100+
externboolexamine_opclause_expression(OpExpr*expr,Var**varp,
101+
Const**cstp,bool*isgtp);
100102

101103
externSelectivitymcv_clauselist_selectivity(PlannerInfo*root,
102104
StatisticExtInfo*stat,

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