From: Tom Lane Date: Tue, 6 Jul 2021 16:36:13 +0000 (-0400) Subject: Avoid doing catalog lookups in postgres_fdw's conversion_error_callback. X-Git-Tag: REL9_6_23~40 X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=67f925bbd9de4ea5d775a72a89d768db38c976ae;p=postgresql.git Avoid doing catalog lookups in postgres_fdw's conversion_error_callback. As in 50371df26, this is a bad idea since the callback can't really know what error is being thrown and thus whether or not it is safe to attempt catalog accesses. Rather than pushing said accesses into the mainline code where they'd usually be a waste of cycles, we can look at the query's rangetable instead. This change does mean that we'll be printing query aliases (if any were used) rather than the table or column's true name. But that doesn't seem like a bad thing: it's certainly a more useful definition in self-join cases, for instance. In any case, it seems unlikely that any applications would be depending on this detail, so it seems safe to change. Patch by me. Original complaint by Andres Freund; Bharath Rupireddy noted the connection to conversion_error_callback. Discussion: https://postgr.es/m/20210106020229.ne5xnuu6wlondjpe@alap3.anarazel.de --- diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index d52e5da234e..6a19c5cd08a 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -2869,15 +2869,17 @@ DROP FUNCTION f_test(int); -- conversion error -- =================================================================== ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE int; -SELECT * FROM ft1 WHERE c1 = 1; -- ERROR +SELECT * FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8) WHERE x1 = 1; -- ERROR ERROR: invalid input syntax for integer: "foo" -CONTEXT: column "c8" of foreign table "ft1" -SELECT ft1.c1, ft2.c2, ft1.c8 FROM ft1, ft2 WHERE ft1.c1 = ft2.c1 AND ft1.c1 = 1; -- ERROR +CONTEXT: column "x8" of foreign table "ftx" +SELECT ftx.x1, ft2.c2, ftx.x8 FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2 + WHERE ftx.x1 = ft2.c1 AND ftx.x1 = 1; -- ERROR ERROR: invalid input syntax for integer: "foo" -CONTEXT: column "c8" of foreign table "ft1" -SELECT ft1.c1, ft2.c2, ft1 FROM ft1, ft2 WHERE ft1.c1 = ft2.c1 AND ft1.c1 = 1; -- ERROR +CONTEXT: column "x8" of foreign table "ftx" +SELECT ftx.x1, ft2.c2, ftx FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2 + WHERE ftx.x1 = ft2.c1 AND ftx.x1 = 1; -- ERROR ERROR: invalid input syntax for integer: "foo" -CONTEXT: whole-row reference to foreign table "ft1" +CONTEXT: whole-row reference to foreign table "ftx" ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE user_enum; -- =================================================================== -- subtransaction diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index 8ed0d6dd7de..07e0c9b6d6d 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -243,16 +243,8 @@ typedef struct PgFdwAnalyzeState */ typedef struct ConversionLocation { - Relation rel; /* foreign table's relcache entry. */ AttrNumber cur_attno; /* attribute number being processed, or 0 */ - - /* - * In case of foreign join push down, fdw_scan_tlist is used to identify - * the Var node corresponding to the error location and - * fsstate->ss.ps.state gives access to the RTEs of corresponding relation - * to get the relation name and attribute name. - */ - ForeignScanState *fsstate; + ForeignScanState *fsstate; /* plan node being processed */ } ConversionLocation; /* Callback argument for ec_member_matches_foreign */ @@ -4454,7 +4446,6 @@ make_tuple_from_result_row(PGresult *res, /* * Set up and install callback to report where conversion error occurs. */ - errpos.rel = rel; errpos.cur_attno = 0; errpos.fsstate = fsstate; errcallback.callback = conversion_error_callback; @@ -4553,61 +4544,77 @@ make_tuple_from_result_row(PGresult *res, /* * Callback function which is called when error occurs during column value * conversion. Print names of column and relation. + * + * Note that this function mustn't do any catalog lookups, since we are in + * an already-failed transaction. Fortunately, we can get the needed info + * from the query's rangetable instead. */ static void conversion_error_callback(void *arg) { + ConversionLocation *errpos = (ConversionLocation *) arg; + ForeignScanState *fsstate = errpos->fsstate; + ForeignScan *fsplan = (ForeignScan *) fsstate->ss.ps.plan; + int varno = 0; + AttrNumber colno = 0; const char *attname = NULL; const char *relname = NULL; bool is_wholerow = false; - ConversionLocation *errpos = (ConversionLocation *) arg; - if (errpos->rel) + if (fsplan->scan.scanrelid > 0) { /* error occurred in a scan against a foreign table */ - TupleDesc tupdesc = RelationGetDescr(errpos->rel); - - if (errpos->cur_attno > 0 && errpos->cur_attno <= tupdesc->natts) - attname = NameStr(tupdesc->attrs[errpos->cur_attno - 1]->attname); - else if (errpos->cur_attno == SelfItemPointerAttributeNumber) - attname = "ctid"; - - relname = RelationGetRelationName(errpos->rel); + varno = fsplan->scan.scanrelid; + colno = errpos->cur_attno; } else { /* error occurred in a scan against a foreign join */ - ForeignScanState *fsstate = errpos->fsstate; - ForeignScan *fsplan = (ForeignScan *) fsstate->ss.ps.plan; - EState *estate = fsstate->ss.ps.state; TargetEntry *tle; - Var *var; - RangeTblEntry *rte; Assert(IsA(fsplan, ForeignScan)); tle = (TargetEntry *) list_nth(fsplan->fdw_scan_tlist, errpos->cur_attno - 1); Assert(IsA(tle, TargetEntry)); - var = (Var *) tle->expr; - Assert(IsA(var, Var)); - - rte = rt_fetch(var->varno, estate->es_range_table); - if (var->varattno == 0) - is_wholerow = true; - else - attname = get_relid_attribute_name(rte->relid, var->varattno); + /* + * Target list can have Vars and expressions. For Vars, we can get + * some information, however for expressions we can't. Thus for + * expressions, just show generic context message. + */ + if (IsA(tle->expr, Var)) + { + Var *var = (Var *) tle->expr; - relname = get_rel_name(rte->relid); + varno = var->varno; + colno = var->varattno; + } } - if (relname) + if (varno > 0) { - if (is_wholerow) - errcontext("whole-row reference to foreign table \"%s\"", relname); - else if (attname) - errcontext("column \"%s\" of foreign table \"%s\"", attname, relname); + EState *estate = fsstate->ss.ps.state; + RangeTblEntry *rte = rt_fetch(varno, estate->es_range_table); + + relname = rte->eref->aliasname; + + if (colno == 0) + is_wholerow = true; + else if (colno > 0 && colno <= list_length(rte->eref->colnames)) + attname = strVal(list_nth(rte->eref->colnames, colno - 1)); + else if (colno == SelfItemPointerAttributeNumber) + attname = "ctid"; + else if (colno == ObjectIdAttributeNumber) + attname = "oid"; } + + if (relname && is_wholerow) + errcontext("whole-row reference to foreign table \"%s\"", relname); + else if (relname && attname) + errcontext("column \"%s\" of foreign table \"%s\"", attname, relname); + else + errcontext("processing expression at position %d in select list", + errpos->cur_attno); } /* diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index d719aa7fcfe..fbefd06d4bc 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -702,9 +702,11 @@ DROP FUNCTION f_test(int); -- conversion error -- =================================================================== ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE int; -SELECT * FROM ft1 WHERE c1 = 1; -- ERROR -SELECT ft1.c1, ft2.c2, ft1.c8 FROM ft1, ft2 WHERE ft1.c1 = ft2.c1 AND ft1.c1 = 1; -- ERROR -SELECT ft1.c1, ft2.c2, ft1 FROM ft1, ft2 WHERE ft1.c1 = ft2.c1 AND ft1.c1 = 1; -- ERROR +SELECT * FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8) WHERE x1 = 1; -- ERROR +SELECT ftx.x1, ft2.c2, ftx.x8 FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2 + WHERE ftx.x1 = ft2.c1 AND ftx.x1 = 1; -- ERROR +SELECT ftx.x1, ft2.c2, ftx FROM ft1 ftx(x1,x2,x3,x4,x5,x6,x7,x8), ft2 + WHERE ftx.x1 = ft2.c1 AND ftx.x1 = 1; -- ERROR ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE user_enum; -- ===================================================================