Postpone calls of unsafe server-side functions in pg_dump.

Avoid calling pg_get_partkeydef(), pg_get_expr(relpartbound),
and regtypeout until we have lock on the relevant tables.
The existing coding is at serious risk of failure if there
are any concurrent DROP TABLE commands going on --- including
drops of other sessions' temp tables.

Arguably this is a bug fix that should be back-patched, but it's
moderately invasive and we've not had all that many complaints
about such failures.  Let's just put it in HEAD for now.

Discussion: https://postgr.es/m/2273648.1634764485@sss.pgh.pa.us
Discussion: https://postgr.es/m/7d7eb6128f40401d81b3b7a898b6b4de@W2012-02.nidsa.loc

src/bin/pg_dump/pg_dump.c

@@ -6272,20 +6272,23 @@ getTables(Archive *fout, int *numTables)
 	int			i_is_identity_sequence;
 	int			i_relacl;
 	int			i_acldefault;
-	int			i_partkeydef;
 	int			i_ispartition;
-	int			i_partbound;
 
 	/*
 	 * Find all the tables and table-like objects.
 	 *
+	 * We must fetch all tables in this phase because otherwise we cannot
+	 * correctly identify inherited columns, owned sequences, etc.
+	 *
 	 * We include system catalogs, so that we can work if a user table is
 	 * defined to inherit from a system catalog (pretty weird, but...)
 	 *
 	 * Note: in this phase we should collect only a minimal amount of
 	 * information about each table, basically just enough to decide if it is
-	 * interesting. We must fetch all tables in this phase because otherwise
+	 * interesting.  In particular, since we do not yet have lock on any user
-	 * we cannot correctly identify inherited columns, owned sequences, etc.
+	 * table, we MUST NOT invoke any server-side data collection functions
+	 * (for instance, pg_get_partkeydef()).  Those are likely to fail or give
+	 * wrong answers if any concurrent DDL is happening.
 	 */
 
 	appendPQExpBuffer(query,
@@ -6379,10 +6382,10 @@ getTables(Archive *fout, int *numTables)
 
 	if (fout->remoteVersion >= 90000)
 		appendPQExpBufferStr(query,
-							 "CASE WHEN c.reloftype <> 0 THEN c.reloftype::pg_catalog.regtype ELSE NULL END AS reloftype, ");
+							 "c.reloftype, ");
 	else
 		appendPQExpBufferStr(query,
-							 "NULL AS reloftype, ");
+							 "0 AS reloftype, ");
 
 	if (fout->remoteVersion >= 90100)
 		appendPQExpBufferStr(query,
@@ -6423,14 +6426,10 @@ getTables(Archive *fout, int *numTables)
 
 	if (fout->remoteVersion >= 100000)
 		appendPQExpBufferStr(query,
-							 "pg_get_partkeydef(c.oid) AS partkeydef, "
+							 "c.relispartition AS ispartition ");
-							 "c.relispartition AS ispartition, "
-							 "pg_get_expr(c.relpartbound, c.oid) AS partbound ");
 	else
 		appendPQExpBufferStr(query,
-							 "NULL AS partkeydef, "
+							 "false AS ispartition ");
-							 "false AS ispartition, "
-							 "NULL AS partbound ");
 
 	/*
 	 * Left join to pg_depend to pick up dependency info linking sequences to
@@ -6539,9 +6538,7 @@ getTables(Archive *fout, int *numTables)
 	i_is_identity_sequence = PQfnumber(res, "is_identity_sequence");
 	i_relacl = PQfnumber(res, "relacl");
 	i_acldefault = PQfnumber(res, "acldefault");
-	i_partkeydef = PQfnumber(res, "partkeydef");
 	i_ispartition = PQfnumber(res, "ispartition");
-	i_partbound = PQfnumber(res, "partbound");
 
 	if (dopt->lockWaitTimeout)
 	{
@@ -6607,19 +6604,14 @@ getTables(Archive *fout, int *numTables)
 		else
 			tblinfo[i].checkoption = pg_strdup(PQgetvalue(res, i, i_checkoption));
 		tblinfo[i].toast_reloptions = pg_strdup(PQgetvalue(res, i, i_toastreloptions));
-		if (PQgetisnull(res, i, i_reloftype))
+		tblinfo[i].reloftype = atooid(PQgetvalue(res, i, i_reloftype));
-			tblinfo[i].reloftype = NULL;
-		else
-			tblinfo[i].reloftype = pg_strdup(PQgetvalue(res, i, i_reloftype));
 		tblinfo[i].foreign_server = atooid(PQgetvalue(res, i, i_foreignserver));
 		if (PQgetisnull(res, i, i_amname))
 			tblinfo[i].amname = NULL;
 		else
 			tblinfo[i].amname = pg_strdup(PQgetvalue(res, i, i_amname));
 		tblinfo[i].is_identity_sequence = (strcmp(PQgetvalue(res, i, i_is_identity_sequence), "t") == 0);
-		tblinfo[i].partkeydef = pg_strdup(PQgetvalue(res, i, i_partkeydef));
 		tblinfo[i].ispartition = (strcmp(PQgetvalue(res, i, i_ispartition), "t") == 0);
-		tblinfo[i].partbound = pg_strdup(PQgetvalue(res, i, i_partbound));
 
 		/* other fields were zeroed above */
 
@@ -15651,12 +15643,34 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 	}
 	else
 	{
+		char	   *partkeydef = NULL;
 		char	   *ftoptions = NULL;
 		char	   *srvname = NULL;
 		char	   *foreign = "";
 
+		/*
+		 * Set reltypename, and collect any relkind-specific data that we
+		 * didn't fetch during getTables().
+		 */
 		switch (tbinfo->relkind)
 		{
+			case RELKIND_PARTITIONED_TABLE:
+				{
+					PQExpBuffer query = createPQExpBuffer();
+					PGresult   *res;
+
+					reltypename = "TABLE";
+
+					/* retrieve partition key definition */
+					appendPQExpBuffer(query,
+									  "SELECT pg_get_partkeydef('%u')",
+									  tbinfo->dobj.catId.oid);
+					res = ExecuteSqlQueryForSingleRow(fout, query->data);
+					partkeydef = pg_strdup(PQgetvalue(res, 0, 0));
+					PQclear(res);
+					destroyPQExpBuffer(query);
+					break;
+				}
 			case RELKIND_FOREIGN_TABLE:
 				{
 					PQExpBuffer query = createPQExpBuffer();
@@ -15696,6 +15710,7 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 				break;
 			default:
 				reltypename = "TABLE";
+				break;
 		}
 
 		numParents = tbinfo->numParents;
@@ -15717,8 +15732,10 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 		 * Attach to type, if reloftype; except in case of a binary upgrade,
 		 * we dump the table normally and attach it to the type afterward.
 		 */
-		if (tbinfo->reloftype && !dopt->binary_upgrade)
+		if (OidIsValid(tbinfo->reloftype) && !dopt->binary_upgrade)
-			appendPQExpBuffer(q, " OF %s", tbinfo->reloftype);
+			appendPQExpBuffer(q, " OF %s",
+							  getFormattedTypeName(fout, tbinfo->reloftype,
+												   zeroIsError));
 
 		if (tbinfo->relkind != RELKIND_MATVIEW)
 		{
@@ -15756,7 +15773,8 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 					 * Skip column if fully defined by reloftype, except in
 					 * binary upgrade
 					 */
-					if (tbinfo->reloftype && !print_default && !print_notnull &&
+					if (OidIsValid(tbinfo->reloftype) &&
+						!print_default && !print_notnull &&
 						!dopt->binary_upgrade)
 						continue;
 
@@ -15789,7 +15807,7 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 					 * table ('OF type_name'), but in binary-upgrade mode,
 					 * print it in that case too.
 					 */
-					if (dopt->binary_upgrade || !tbinfo->reloftype)
+					if (dopt->binary_upgrade || !OidIsValid(tbinfo->reloftype))
 					{
 						appendPQExpBuffer(q, " %s",
 										  tbinfo->atttypnames[j]);
@@ -15852,7 +15870,7 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 
 			if (actual_atts)
 				appendPQExpBufferStr(q, "\n)");
-			else if (!(tbinfo->reloftype && !dopt->binary_upgrade))
+			else if (!(OidIsValid(tbinfo->reloftype) && !dopt->binary_upgrade))
 			{
 				/*
 				 * No attributes? we must have a parenthesized attribute list,
@@ -15881,7 +15899,7 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 			}
 
 			if (tbinfo->relkind == RELKIND_PARTITIONED_TABLE)
-				appendPQExpBuffer(q, "\nPARTITION BY %s", tbinfo->partkeydef);
+				appendPQExpBuffer(q, "\nPARTITION BY %s", partkeydef);
 
 			if (tbinfo->relkind == RELKIND_FOREIGN_TABLE)
 				appendPQExpBuffer(q, "\nSERVER %s", fmtId(srvname));
@@ -16064,12 +16082,13 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 				}
 			}
 
-			if (tbinfo->reloftype)
+			if (OidIsValid(tbinfo->reloftype))
 			{
 				appendPQExpBufferStr(q, "\n-- For binary upgrade, set up typed tables this way.\n");
 				appendPQExpBuffer(q, "ALTER TABLE ONLY %s OF %s;\n",
 								  qualrelname,
-								  tbinfo->reloftype);
+								  getFormattedTypeName(fout, tbinfo->reloftype,
+													   zeroIsError));
 			}
 		}
 
@@ -16242,6 +16261,8 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 								  tbinfo->attfdwoptions[j]);
 		}						/* end loop over columns */
 
+		if (partkeydef)
+			free(partkeydef);
 		if (ftoptions)
 			free(ftoptions);
 		if (srvname)
@@ -16358,6 +16379,8 @@ dumpTableAttach(Archive *fout, const TableAttachInfo *attachinfo)
 {
 	DumpOptions *dopt = fout->dopt;
 	PQExpBuffer q;
+	PGresult   *res;
+	char	   *partbound;
 
 	/* Do nothing in data-only dump */
 	if (dopt->dataOnly)
@@ -16368,14 +16391,23 @@ dumpTableAttach(Archive *fout, const TableAttachInfo *attachinfo)
 
 	q = createPQExpBuffer();
 
-	/* Perform ALTER TABLE on the parent */
+	/* Fetch the partition's partbound */
 	appendPQExpBuffer(q,
+					  "SELECT pg_get_expr(c.relpartbound, c.oid) "
+					  "FROM pg_class c "
+					  "WHERE c.oid = '%u'",
+					  attachinfo->partitionTbl->dobj.catId.oid);
+	res = ExecuteSqlQueryForSingleRow(fout, q->data);
+	partbound = PQgetvalue(res, 0, 0);
+
+	/* Perform ALTER TABLE on the parent */
+	printfPQExpBuffer(q,
 					  "ALTER TABLE ONLY %s ",
 					  fmtQualifiedDumpable(attachinfo->parentTbl));
 	appendPQExpBuffer(q,
 					  "ATTACH PARTITION %s %s;\n",
 					  fmtQualifiedDumpable(attachinfo->partitionTbl),
-					  attachinfo->partitionTbl->partbound);
+					  partbound);
 
 	/*
 	 * There is no point in creating a drop query as the drop is done by table
@@ -16392,6 +16424,7 @@ dumpTableAttach(Archive *fout, const TableAttachInfo *attachinfo)
 							  .section = SECTION_PRE_DATA,
 							  .createStmt = q->data));
 
+	PQclear(res);
 	destroyPQExpBuffer(q);
 }
 

src/bin/pg_dump/pg_dump.h

@@ -308,7 +308,7 @@ typedef struct _tableInfo
 	uint32		toast_minmxid;	/* toast table's relminmxid */
 	int			ncheck;			/* # of CHECK expressions */
 	Oid			reltype;		/* OID of table's composite type, if any */
-	char	   *reloftype;		/* underlying type for typed table */
+	Oid			reloftype;		/* underlying type for typed table */
 	Oid			foreign_server; /* foreign server oid, if applicable */
 	/* these two are set only if table is a sequence owned by a column: */
 	Oid			owning_tab;		/* OID of table owning sequence */
@@ -347,8 +347,6 @@ typedef struct _tableInfo
 	bool	   *inhNotNull;		/* true if NOT NULL is inherited */
 	struct _attrDefInfo **attrdefs; /* DEFAULT expressions */
 	struct _constraintInfo *checkexprs; /* CHECK constraints */
-	char	   *partkeydef;		/* partition key definition */
-	char	   *partbound;		/* partition bound definition */
 	bool		needs_override; /* has GENERATED ALWAYS AS IDENTITY */
 	char	   *amname;			/* relation access method */