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Commit3071bbf

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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 parentdb692b0 commit3071bbf

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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
@@ -4200,6 +4200,9 @@ CONTEXT: whole-row reference to foreign table "ftx"
42004200
SELECT sum(c2), array_agg(c8) FROM ft1 GROUP BY c8; -- ERROR
42014201
ERROR: invalid input syntax for type integer: "foo"
42024202
CONTEXT: processing expression at position 2 in select list
4203+
ANALYZE ft1; -- ERROR
4204+
ERROR: invalid input syntax for type integer: "foo"
4205+
CONTEXT: column "c8" of foreign table "ft1"
42034206
ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE user_enum;
42044207
-- ===================================================================
42054208
-- 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 */
@@ -7113,7 +7114,12 @@ complete_pending_request(AsyncRequest *areq)
71137114
* rel is the local representation of the foreign table, attinmeta is
71147115
* conversion data for the rel's tupdesc, and retrieved_attrs is an
71157116
* integer list of the table column numbers present in the PGresult.
7117+
* fsstate is the ForeignScan plan node's execution state.
71167118
* temp_context is a working context that can be reset after each tuple.
7119+
*
7120+
* Note: either rel or fsstate, but not both, can be NULL. rel is NULL
7121+
* if we're processing a remote join, while fsstate is NULL in a non-query
7122+
* context such as ANALYZE, or if we're processing a non-scan query node.
71177123
*/
71187124
staticHeapTuple
71197125
make_tuple_from_result_row(PGresult*res,
@@ -7144,6 +7150,10 @@ make_tuple_from_result_row(PGresult *res,
71447150
*/
71457151
oldcontext=MemoryContextSwitchTo(temp_context);
71467152

7153+
/*
7154+
* Get the tuple descriptor for the row. Use the rel's tupdesc if rel is
7155+
* provided, otherwise look to the scan node's ScanTupleSlot.
7156+
*/
71477157
if (rel)
71487158
tupdesc=RelationGetDescr(rel);
71497159
else
@@ -7161,6 +7171,7 @@ make_tuple_from_result_row(PGresult *res,
71617171
* Set up and install callback to report where conversion error occurs.
71627172
*/
71637173
errpos.cur_attno=0;
7174+
errpos.rel=rel;
71647175
errpos.fsstate=fsstate;
71657176
errcallback.callback=conversion_error_callback;
71667177
errcallback.arg= (void*)&errpos;
@@ -7265,60 +7276,87 @@ make_tuple_from_result_row(PGresult *res,
72657276
*
72667277
* Note that this function mustn't do any catalog lookups, since we are in
72677278
* an already-failed transaction. Fortunately, we can get the needed info
7268-
* from the query's rangetable instead.
7279+
* from therelation or thequery's rangetable instead.
72697280
*/
72707281
staticvoid
72717282
conversion_error_callback(void*arg)
72727283
{
72737284
ConversionLocation*errpos= (ConversionLocation*)arg;
7285+
Relationrel=errpos->rel;
72747286
ForeignScanState*fsstate=errpos->fsstate;
7275-
ForeignScan*fsplan=castNode(ForeignScan,fsstate->ss.ps.plan);
7276-
intvarno=0;
7277-
AttrNumbercolno=0;
72787287
constchar*attname=NULL;
72797288
constchar*relname=NULL;
72807289
boolis_wholerow= false;
72817290

7282-
if (fsplan->scan.scanrelid>0)
7283-
{
7284-
/* error occurred in a scan against a foreign table */
7285-
varno=fsplan->scan.scanrelid;
7286-
colno=errpos->cur_attno;
7287-
}
7288-
else
7291+
/*
7292+
* If we're in a scan node, always use aliases from the rangetable, for
7293+
* consistency between the simple-relation and remote-join cases. Look at
7294+
* the relation's tupdesc only if we're not in a scan node.
7295+
*/
7296+
if (fsstate)
72897297
{
7290-
/* error occurred in a scan against a foreign join */
7291-
TargetEntry*tle;
7298+
/* ForeignScan case */
7299+
ForeignScan*fsplan=castNode(ForeignScan,fsstate->ss.ps.plan);
7300+
intvarno=0;
7301+
AttrNumbercolno=0;
72927302

7293-
tle=list_nth_node(TargetEntry,fsplan->fdw_scan_tlist,
7294-
errpos->cur_attno-1);
7303+
if (fsplan->scan.scanrelid>0)
7304+
{
7305+
/* error occurred in a scan against a foreign table */
7306+
varno=fsplan->scan.scanrelid;
7307+
colno=errpos->cur_attno;
7308+
}
7309+
else
7310+
{
7311+
/* error occurred in a scan against a foreign join */
7312+
TargetEntry*tle;
72957313

7296-
/*
7297-
* Target list can have Vars and expressions. For Vars, we can get
7298-
* some information, however for expressions we can't. Thus for
7299-
* expressions, just show generic context message.
7300-
*/
7301-
if (IsA(tle->expr,Var))
7314+
tle=list_nth_node(TargetEntry,fsplan->fdw_scan_tlist,
7315+
errpos->cur_attno-1);
7316+
7317+
/*
7318+
* Target list can have Vars and expressions. For Vars, we can
7319+
* get some information, however for expressions we can't. Thus
7320+
* for expressions, just show generic context message.
7321+
*/
7322+
if (IsA(tle->expr,Var))
7323+
{
7324+
Var*var= (Var*)tle->expr;
7325+
7326+
varno=var->varno;
7327+
colno=var->varattno;
7328+
}
7329+
}
7330+
7331+
if (varno>0)
73027332
{
7303-
Var*var= (Var*)tle->expr;
7333+
EState*estate=fsstate->ss.ps.state;
7334+
RangeTblEntry*rte=exec_rt_fetch(varno,estate);
73047335

7305-
varno=var->varno;
7306-
colno=var->varattno;
7336+
relname=rte->eref->aliasname;
7337+
7338+
if (colno==0)
7339+
is_wholerow= true;
7340+
elseif (colno>0&&colno <=list_length(rte->eref->colnames))
7341+
attname=strVal(list_nth(rte->eref->colnames,colno-1));
7342+
elseif (colno==SelfItemPointerAttributeNumber)
7343+
attname="ctid";
73077344
}
73087345
}
7309-
7310-
if (varno>0)
7346+
elseif (rel)
73117347
{
7312-
EState*estate=fsstate->ss.ps.state;
7313-
RangeTblEntry*rte=exec_rt_fetch(varno,estate);
7348+
/* Non-ForeignScan case (we should always have a rel here) */
7349+
TupleDesctupdesc=RelationGetDescr(rel);
73147350

7315-
relname=rte->eref->aliasname;
7351+
relname=RelationGetRelationName(rel);
7352+
if (errpos->cur_attno>0&&errpos->cur_attno <=tupdesc->natts)
7353+
{
7354+
Form_pg_attributeattr=TupleDescAttr(tupdesc,
7355+
errpos->cur_attno-1);
73167356

7317-
if (colno==0)
7318-
is_wholerow= true;
7319-
elseif (colno>0&&colno <=list_length(rte->eref->colnames))
7320-
attname=strVal(list_nth(rte->eref->colnames,colno-1));
7321-
elseif (colno==SelfItemPointerAttributeNumber)
7357+
attname=NameStr(attr->attname);
7358+
}
7359+
elseif (errpos->cur_attno==SelfItemPointerAttributeNumber)
73227360
attname="ctid";
73237361
}
73247362

‎contrib/postgres_fdw/sql/postgres_fdw.sql

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1164,6 +1164,7 @@ SELECT ftx.x1, ft2.c2, ftx.x8 FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2
11641164
SELECTftx.x1,ft2.c2, ftxFROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2
11651165
WHEREftx.x1=ft2.c1ANDftx.x1=1;-- ERROR
11661166
SELECTsum(c2), array_agg(c8)FROM ft1GROUP BY c8;-- ERROR
1167+
ANALYZE ft1;-- ERROR
11671168
ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE user_enum;
11681169

11691170
-- ===================================================================

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