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Commit12ff678

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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 parent8e26b86 commit12ff678

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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
@@ -4110,6 +4110,9 @@ CONTEXT: whole-row reference to foreign table "ftx"
41104110
SELECT sum(c2), array_agg(c8) FROM ft1 GROUP BY c8; -- ERROR
41114111
ERROR: invalid input syntax for type integer: "foo"
41124112
CONTEXT: processing expression at position 2 in select list
4113+
ANALYZE ft1; -- ERROR
4114+
ERROR: invalid input syntax for type integer: "foo"
4115+
CONTEXT: column "c8" of foreign table "ft1"
41134116
ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE user_enum;
41144117
-- ===================================================================
41154118
-- subtransaction

‎contrib/postgres_fdw/postgres_fdw.c

Lines changed: 73 additions & 35 deletions
Original file line numberDiff line numberDiff line change
@@ -303,7 +303,8 @@ typedef struct
303303
typedefstructConversionLocation
304304
{
305305
AttrNumbercur_attno;/* attribute number being processed, or 0 */
306-
ForeignScanState*fsstate;/* plan node being processed */
306+
Relationrel;/* foreign table being processed, or NULL */
307+
ForeignScanState*fsstate;/* plan node being processed, or NULL */
307308
}ConversionLocation;
308309

309310
/* Callback argument for ec_member_matches_foreign */
@@ -7117,7 +7118,12 @@ complete_pending_request(AsyncRequest *areq)
71177118
* rel is the local representation of the foreign table, attinmeta is
71187119
* conversion data for the rel's tupdesc, and retrieved_attrs is an
71197120
* integer list of the table column numbers present in the PGresult.
7121+
* fsstate is the ForeignScan plan node's execution state.
71207122
* temp_context is a working context that can be reset after each tuple.
7123+
*
7124+
* Note: either rel or fsstate, but not both, can be NULL. rel is NULL
7125+
* if we're processing a remote join, while fsstate is NULL in a non-query
7126+
* context such as ANALYZE, or if we're processing a non-scan query node.
71217127
*/
71227128
staticHeapTuple
71237129
make_tuple_from_result_row(PGresult*res,
@@ -7148,6 +7154,10 @@ make_tuple_from_result_row(PGresult *res,
71487154
*/
71497155
oldcontext=MemoryContextSwitchTo(temp_context);
71507156

7157+
/*
7158+
* Get the tuple descriptor for the row. Use the rel's tupdesc if rel is
7159+
* provided, otherwise look to the scan node's ScanTupleSlot.
7160+
*/
71517161
if (rel)
71527162
tupdesc=RelationGetDescr(rel);
71537163
else
@@ -7165,6 +7175,7 @@ make_tuple_from_result_row(PGresult *res,
71657175
* Set up and install callback to report where conversion error occurs.
71667176
*/
71677177
errpos.cur_attno=0;
7178+
errpos.rel=rel;
71687179
errpos.fsstate=fsstate;
71697180
errcallback.callback=conversion_error_callback;
71707181
errcallback.arg= (void*)&errpos;
@@ -7269,60 +7280,87 @@ make_tuple_from_result_row(PGresult *res,
72697280
*
72707281
* Note that this function mustn't do any catalog lookups, since we are in
72717282
* an already-failed transaction. Fortunately, we can get the needed info
7272-
* from the query's rangetable instead.
7283+
* from therelation or thequery's rangetable instead.
72737284
*/
72747285
staticvoid
72757286
conversion_error_callback(void*arg)
72767287
{
72777288
ConversionLocation*errpos= (ConversionLocation*)arg;
7289+
Relationrel=errpos->rel;
72787290
ForeignScanState*fsstate=errpos->fsstate;
7279-
ForeignScan*fsplan=castNode(ForeignScan,fsstate->ss.ps.plan);
7280-
intvarno=0;
7281-
AttrNumbercolno=0;
72827291
constchar*attname=NULL;
72837292
constchar*relname=NULL;
72847293
boolis_wholerow= false;
72857294

7286-
if (fsplan->scan.scanrelid>0)
7287-
{
7288-
/* error occurred in a scan against a foreign table */
7289-
varno=fsplan->scan.scanrelid;
7290-
colno=errpos->cur_attno;
7291-
}
7292-
else
7295+
/*
7296+
* If we're in a scan node, always use aliases from the rangetable, for
7297+
* consistency between the simple-relation and remote-join cases. Look at
7298+
* the relation's tupdesc only if we're not in a scan node.
7299+
*/
7300+
if (fsstate)
72937301
{
7294-
/* error occurred in a scan against a foreign join */
7295-
TargetEntry*tle;
7302+
/* ForeignScan case */
7303+
ForeignScan*fsplan=castNode(ForeignScan,fsstate->ss.ps.plan);
7304+
intvarno=0;
7305+
AttrNumbercolno=0;
72967306

7297-
tle=list_nth_node(TargetEntry,fsplan->fdw_scan_tlist,
7298-
errpos->cur_attno-1);
7307+
if (fsplan->scan.scanrelid>0)
7308+
{
7309+
/* error occurred in a scan against a foreign table */
7310+
varno=fsplan->scan.scanrelid;
7311+
colno=errpos->cur_attno;
7312+
}
7313+
else
7314+
{
7315+
/* error occurred in a scan against a foreign join */
7316+
TargetEntry*tle;
72997317

7300-
/*
7301-
* Target list can have Vars and expressions. For Vars, we can get
7302-
* some information, however for expressions we can't. Thus for
7303-
* expressions, just show generic context message.
7304-
*/
7305-
if (IsA(tle->expr,Var))
7318+
tle=list_nth_node(TargetEntry,fsplan->fdw_scan_tlist,
7319+
errpos->cur_attno-1);
7320+
7321+
/*
7322+
* Target list can have Vars and expressions. For Vars, we can
7323+
* get some information, however for expressions we can't. Thus
7324+
* for expressions, just show generic context message.
7325+
*/
7326+
if (IsA(tle->expr,Var))
7327+
{
7328+
Var*var= (Var*)tle->expr;
7329+
7330+
varno=var->varno;
7331+
colno=var->varattno;
7332+
}
7333+
}
7334+
7335+
if (varno>0)
73067336
{
7307-
Var*var= (Var*)tle->expr;
7337+
EState*estate=fsstate->ss.ps.state;
7338+
RangeTblEntry*rte=exec_rt_fetch(varno,estate);
73087339

7309-
varno=var->varno;
7310-
colno=var->varattno;
7340+
relname=rte->eref->aliasname;
7341+
7342+
if (colno==0)
7343+
is_wholerow= true;
7344+
elseif (colno>0&&colno <=list_length(rte->eref->colnames))
7345+
attname=strVal(list_nth(rte->eref->colnames,colno-1));
7346+
elseif (colno==SelfItemPointerAttributeNumber)
7347+
attname="ctid";
73117348
}
73127349
}
7313-
7314-
if (varno>0)
7350+
elseif (rel)
73157351
{
7316-
EState*estate=fsstate->ss.ps.state;
7317-
RangeTblEntry*rte=exec_rt_fetch(varno,estate);
7352+
/* Non-ForeignScan case (we should always have a rel here) */
7353+
TupleDesctupdesc=RelationGetDescr(rel);
73187354

7319-
relname=rte->eref->aliasname;
7355+
relname=RelationGetRelationName(rel);
7356+
if (errpos->cur_attno>0&&errpos->cur_attno <=tupdesc->natts)
7357+
{
7358+
Form_pg_attributeattr=TupleDescAttr(tupdesc,
7359+
errpos->cur_attno-1);
73207360

7321-
if (colno==0)
7322-
is_wholerow= true;
7323-
elseif (colno>0&&colno <=list_length(rte->eref->colnames))
7324-
attname=strVal(list_nth(rte->eref->colnames,colno-1));
7325-
elseif (colno==SelfItemPointerAttributeNumber)
7361+
attname=NameStr(attr->attname);
7362+
}
7363+
elseif (errpos->cur_attno==SelfItemPointerAttributeNumber)
73267364
attname="ctid";
73277365
}
73287366

‎contrib/postgres_fdw/sql/postgres_fdw.sql

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1135,6 +1135,7 @@ SELECT ftx.x1, ft2.c2, ftx.x8 FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2
11351135
SELECTftx.x1,ft2.c2, ftxFROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2
11361136
WHEREftx.x1=ft2.c1ANDftx.x1=1;-- ERROR
11371137
SELECTsum(c2), array_agg(c8)FROM ft1GROUP BY c8;-- ERROR
1138+
ANALYZE ft1;-- ERROR
11381139
ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE user_enum;
11391140

11401141
-- ===================================================================

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