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Commit2288973

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Fix null-pointer crash in postgres_fdw's conversion_error_callback.
Commitc7b7311 adjusted conversion_error_callback to always useinformation from the query's rangetable, to avoid doing catalog lookupsin an already-failed transaction. However, as a result of the utterlyinadequate documentation for make_tuple_from_result_row, I failed torealize that fsstate could be NULL in some contexts. That led to acrash if we got a conversion error in such a context. Fix by fallingback to the previous coding when fsstate is NULL. Improve thecommentary, too.Per report from Andrey Borodin. Back-patch to 9.6, like the previouspatch.Discussion:https://postgr.es/m/08916396-55E4-4D68-AB3A-BD6066F9E5C0@yandex-team.ru
1 parent6762180 commit2288973

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3 files changed

+77
-35
lines changed

3 files changed

+77
-35
lines changed

‎contrib/postgres_fdw/expected/postgres_fdw.out

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -4049,6 +4049,9 @@ CONTEXT: whole-row reference to foreign table "ftx"
40494049
SELECT sum(c2), array_agg(c8) FROM ft1 GROUP BY c8; -- ERROR
40504050
ERROR: invalid input syntax for type integer: "foo"
40514051
CONTEXT: processing expression at position 2 in select list
4052+
ANALYZE ft1; -- ERROR
4053+
ERROR: invalid input syntax for type integer: "foo"
4054+
CONTEXT: column "c8" of foreign table "ft1"
40524055
ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE user_enum;
40534056
-- ===================================================================
40544057
-- subtransaction

‎contrib/postgres_fdw/postgres_fdw.c

Lines changed: 73 additions & 35 deletions
Original file line numberDiff line numberDiff line change
@@ -285,7 +285,8 @@ typedef struct
285285
typedefstructConversionLocation
286286
{
287287
AttrNumbercur_attno;/* attribute number being processed, or 0 */
288-
ForeignScanState*fsstate;/* plan node being processed */
288+
Relationrel;/* foreign table being processed, or NULL */
289+
ForeignScanState*fsstate;/* plan node being processed, or NULL */
289290
}ConversionLocation;
290291

291292
/* Callback argument for ec_member_matches_foreign */
@@ -6293,7 +6294,12 @@ add_foreign_final_paths(PlannerInfo *root, RelOptInfo *input_rel,
62936294
* rel is the local representation of the foreign table, attinmeta is
62946295
* conversion data for the rel's tupdesc, and retrieved_attrs is an
62956296
* integer list of the table column numbers present in the PGresult.
6297+
* fsstate is the ForeignScan plan node's execution state.
62966298
* temp_context is a working context that can be reset after each tuple.
6299+
*
6300+
* Note: either rel or fsstate, but not both, can be NULL. rel is NULL
6301+
* if we're processing a remote join, while fsstate is NULL in a non-query
6302+
* context such as ANALYZE, or if we're processing a non-scan query node.
62976303
*/
62986304
staticHeapTuple
62996305
make_tuple_from_result_row(PGresult*res,
@@ -6324,6 +6330,10 @@ make_tuple_from_result_row(PGresult *res,
63246330
*/
63256331
oldcontext=MemoryContextSwitchTo(temp_context);
63266332

6333+
/*
6334+
* Get the tuple descriptor for the row. Use the rel's tupdesc if rel is
6335+
* provided, otherwise look to the scan node's ScanTupleSlot.
6336+
*/
63276337
if (rel)
63286338
tupdesc=RelationGetDescr(rel);
63296339
else
@@ -6341,6 +6351,7 @@ make_tuple_from_result_row(PGresult *res,
63416351
* Set up and install callback to report where conversion error occurs.
63426352
*/
63436353
errpos.cur_attno=0;
6354+
errpos.rel=rel;
63446355
errpos.fsstate=fsstate;
63456356
errcallback.callback=conversion_error_callback;
63466357
errcallback.arg= (void*)&errpos;
@@ -6445,60 +6456,87 @@ make_tuple_from_result_row(PGresult *res,
64456456
*
64466457
* Note that this function mustn't do any catalog lookups, since we are in
64476458
* an already-failed transaction. Fortunately, we can get the needed info
6448-
* from the query's rangetable instead.
6459+
* from therelation or thequery's rangetable instead.
64496460
*/
64506461
staticvoid
64516462
conversion_error_callback(void*arg)
64526463
{
64536464
ConversionLocation*errpos= (ConversionLocation*)arg;
6465+
Relationrel=errpos->rel;
64546466
ForeignScanState*fsstate=errpos->fsstate;
6455-
ForeignScan*fsplan=castNode(ForeignScan,fsstate->ss.ps.plan);
6456-
intvarno=0;
6457-
AttrNumbercolno=0;
64586467
constchar*attname=NULL;
64596468
constchar*relname=NULL;
64606469
boolis_wholerow= false;
64616470

6462-
if (fsplan->scan.scanrelid>0)
6463-
{
6464-
/* error occurred in a scan against a foreign table */
6465-
varno=fsplan->scan.scanrelid;
6466-
colno=errpos->cur_attno;
6467-
}
6468-
else
6471+
/*
6472+
* If we're in a scan node, always use aliases from the rangetable, for
6473+
* consistency between the simple-relation and remote-join cases. Look at
6474+
* the relation's tupdesc only if we're not in a scan node.
6475+
*/
6476+
if (fsstate)
64696477
{
6470-
/* error occurred in a scan against a foreign join */
6471-
TargetEntry*tle;
6478+
/* ForeignScan case */
6479+
ForeignScan*fsplan=castNode(ForeignScan,fsstate->ss.ps.plan);
6480+
intvarno=0;
6481+
AttrNumbercolno=0;
64726482

6473-
tle=list_nth_node(TargetEntry,fsplan->fdw_scan_tlist,
6474-
errpos->cur_attno-1);
6483+
if (fsplan->scan.scanrelid>0)
6484+
{
6485+
/* error occurred in a scan against a foreign table */
6486+
varno=fsplan->scan.scanrelid;
6487+
colno=errpos->cur_attno;
6488+
}
6489+
else
6490+
{
6491+
/* error occurred in a scan against a foreign join */
6492+
TargetEntry*tle;
64756493

6476-
/*
6477-
* Target list can have Vars and expressions. For Vars, we can get
6478-
* some information, however for expressions we can't. Thus for
6479-
* expressions, just show generic context message.
6480-
*/
6481-
if (IsA(tle->expr,Var))
6494+
tle=list_nth_node(TargetEntry,fsplan->fdw_scan_tlist,
6495+
errpos->cur_attno-1);
6496+
6497+
/*
6498+
* Target list can have Vars and expressions. For Vars, we can
6499+
* get some information, however for expressions we can't. Thus
6500+
* for expressions, just show generic context message.
6501+
*/
6502+
if (IsA(tle->expr,Var))
6503+
{
6504+
Var*var= (Var*)tle->expr;
6505+
6506+
varno=var->varno;
6507+
colno=var->varattno;
6508+
}
6509+
}
6510+
6511+
if (varno>0)
64826512
{
6483-
Var*var= (Var*)tle->expr;
6513+
EState*estate=fsstate->ss.ps.state;
6514+
RangeTblEntry*rte=exec_rt_fetch(varno,estate);
64846515

6485-
varno=var->varno;
6486-
colno=var->varattno;
6516+
relname=rte->eref->aliasname;
6517+
6518+
if (colno==0)
6519+
is_wholerow= true;
6520+
elseif (colno>0&&colno <=list_length(rte->eref->colnames))
6521+
attname=strVal(list_nth(rte->eref->colnames,colno-1));
6522+
elseif (colno==SelfItemPointerAttributeNumber)
6523+
attname="ctid";
64876524
}
64886525
}
6489-
6490-
if (varno>0)
6526+
elseif (rel)
64916527
{
6492-
EState*estate=fsstate->ss.ps.state;
6493-
RangeTblEntry*rte=exec_rt_fetch(varno,estate);
6528+
/* Non-ForeignScan case (we should always have a rel here) */
6529+
TupleDesctupdesc=RelationGetDescr(rel);
64946530

6495-
relname=rte->eref->aliasname;
6531+
relname=RelationGetRelationName(rel);
6532+
if (errpos->cur_attno>0&&errpos->cur_attno <=tupdesc->natts)
6533+
{
6534+
Form_pg_attributeattr=TupleDescAttr(tupdesc,
6535+
errpos->cur_attno-1);
64966536

6497-
if (colno==0)
6498-
is_wholerow= true;
6499-
elseif (colno>0&&colno <=list_length(rte->eref->colnames))
6500-
attname=strVal(list_nth(rte->eref->colnames,colno-1));
6501-
elseif (colno==SelfItemPointerAttributeNumber)
6537+
attname=NameStr(attr->attname);
6538+
}
6539+
elseif (errpos->cur_attno==SelfItemPointerAttributeNumber)
65026540
attname="ctid";
65036541
}
65046542

‎contrib/postgres_fdw/sql/postgres_fdw.sql

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1078,6 +1078,7 @@ SELECT ftx.x1, ft2.c2, ftx.x8 FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2
10781078
SELECTftx.x1,ft2.c2, ftxFROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2
10791079
WHEREftx.x1=ft2.c1ANDftx.x1=1;-- ERROR
10801080
SELECTsum(c2), array_agg(c8)FROM ft1GROUP BY c8;-- ERROR
1081+
ANALYZE ft1;-- ERROR
10811082
ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE user_enum;
10821083

10831084
-- ===================================================================

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