Fix partitioned index creation with foreign partitions

When a partitioned tables contains foreign tables as partitions, it is
not possible to implement unique or primary key indexes -- but when
regular indexes are created, there is no reason to do anything other
than ignoring such partitions.  We were raising errors upon encountering
the foreign partitions, which is unfriendly and doesn't protect against
any actual problems.

Relax this restriction so that index creation is allowed on partitioned
tables containing foreign partitions, becoming a no-op on them.  (We may
later want to redefine this so that the FDW is told to create the
indexes on the foreign side.)  This applies to CREATE INDEX, as well as
ALTER TABLE / ATTACH PARTITION and CREATE TABLE / PARTITION OF.

Backpatch to 11, where indexes on partitioned tables were introduced.

Discussion: https://postgr.es/m/15724-d5a58fa9472eef4f@postgresql.org
Author: Álvaro Herrera
Reviewed-by: Amit Langote

7 files changed, 172 insertions, 9 deletions

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index f5ad7659f72..90bf19564c6 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -845,7 +845,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       as if <command>ALTER INDEX ATTACH PARTITION</command> had been executed.
       Note that if the existing table is a foreign table, it is currently not
       allowed to attach the table as a partition of the target table if there
-      are indexes on the target table.  (See also
+      are <literal>UNIQUE</literal> indexes on the target table.  (See also
       <xref linkend="sql-createforeigntable"/>.)
      </para>
 
diff --git a/doc/src/sgml/ref/create_foreign_table.sgml b/doc/src/sgml/ref/create_foreign_table.sgml
index 25d2f09ed20..9d266f272a7 100644
--- a/doc/src/sgml/ref/create_foreign_table.sgml
+++ b/doc/src/sgml/ref/create_foreign_table.sgml
@@ -170,8 +170,8 @@ CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ]
       See the similar form of
       <xref linkend="sql-createtable"/> for more details.
       Note that it is currently not allowed to create the foreign table as a
-      partition of the parent table if there are indexes on the parent table.
-      (See also
+      partition of the parent table if there are <literal>UNIQUE</literal>
+      indexes on the parent table.  (See also
       <link linkend="sql-altertable"><command>ALTER TABLE ATTACH PARTITION</command></link>.)
      </para>
     </listitem>
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index a3cbeff9500..cdbb56f1a4a 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -1085,6 +1085,26 @@ DefineIndex(Oid relationId,
 				int			maplen;
 
 				childrel = table_open(childRelid, lockmode);
+
+				/*
+				 * Don't try to create indexes on foreign tables, though.
+				 * Skip those if a regular index, or fail if trying to create
+				 * a constraint index.
+				 */
+				if (childrel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
+				{
+					if (stmt->unique || stmt->primary)
+						ereport(ERROR,
+								(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+								 errmsg("cannot create unique index on partitioned table \"%s\"",
+										RelationGetRelationName(rel)),
+								 errdetail("Table \"%s\" contains partitions that are foreign tables.",
+										RelationGetRelationName(rel))));
+
+					table_close(childrel, lockmode);
+					continue;
+				}
+
 				childidxs = RelationGetIndexList(childrel);
 				attmap =
 					convert_tuples_by_name_map(RelationGetDescr(childrel),
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ba59fc708a9..7dcd634a1ae 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -1069,6 +1069,22 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
 			IndexStmt  *idxstmt;
 			Oid			constraintOid;
 
+			if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
+			{
+				if (idxRel->rd_index->indisunique)
+					ereport(ERROR,
+							(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+							 errmsg("cannot create foreign partition of partitioned table \"%s\"",
+									RelationGetRelationName(parent)),
+							 errdetail("Table \"%s\" contains indexes that are unique.",
+									RelationGetRelationName(parent))));
+				else
+				{
+					index_close(idxRel, AccessShareLock);
+					continue;
+				}
+			}
+
 			attmap = convert_tuples_by_name_map(RelationGetDescr(rel),
 												RelationGetDescr(parent),
 												gettext_noop("could not convert row type"));
@@ -15723,6 +15739,34 @@ AttachPartitionEnsureIndexes(Relation rel, Relation attachrel)
 	}
 
 	/*
+	 * If we're attaching a foreign table, we must fail if any of the indexes
+	 * is a constraint index; otherwise, there's nothing to do here.  Do this
+	 * before starting work, to avoid wasting the effort of building a few
+	 * non-unique indexes before coming across a unique one.
+	 */
+	if (attachrel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
+	{
+		foreach(cell, idxes)
+		{
+			Oid			idx = lfirst_oid(cell);
+			Relation	idxRel = index_open(idx, AccessShareLock);
+
+			if (idxRel->rd_index->indisunique ||
+				idxRel->rd_index->indisprimary)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("cannot attach foreign table \"%s\" as partition of partitioned table \"%s\"",
+								RelationGetRelationName(attachrel),
+								RelationGetRelationName(rel)),
+						 errdetail("Table \"%s\" contains unique indexes.",
+								   RelationGetRelationName(rel))));
+			index_close(idxRel, AccessShareLock);
+		}
+
+		goto out;
+	}
+
+	/*
 	 * For each index on the partitioned table, find a matching one in the
 	 * partition-to-be; if one is not found, create one.
 	 */
@@ -15824,6 +15868,7 @@ AttachPartitionEnsureIndexes(Relation rel, Relation attachrel)
 		index_close(idxRel, AccessShareLock);
 	}
 
+out:
 	/* Clean up. */
 	for (i = 0; i < list_length(attachRelIdxs); i++)
 		index_close(attachrelIdxRels[i], AccessShareLock);
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 9578b5c7619..05ec7f3ac61 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -1347,10 +1347,16 @@ ProcessUtilitySlow(ParseState *pstate,
 
 							if (relkind != RELKIND_RELATION &&
 								relkind != RELKIND_MATVIEW &&
-								relkind != RELKIND_PARTITIONED_TABLE)
+								relkind != RELKIND_PARTITIONED_TABLE &&
+								relkind != RELKIND_FOREIGN_TABLE)
+								elog(ERROR, "unexpected relkind \"%c\" on partition \"%s\"",
+									 relkind, stmt->relation->relname);
+
+							if (relkind == RELKIND_FOREIGN_TABLE &&
+								(stmt->unique || stmt->primary))
 								ereport(ERROR,
-										(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
-										 errmsg("cannot create index on partitioned table \"%s\"",
+										(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+										 errmsg("cannot create unique index on partitioned table \"%s\"",
 												stmt->relation->relname),
 										 errdetail("Table \"%s\" contains partitions that are foreign tables.",
 												   stmt->relation->relname)));
diff --git a/src/test/regress/expected/foreign_data.out b/src/test/regress/expected/foreign_data.out
index c81e4bda807..b9e25820bc0 100644
--- a/src/test/regress/expected/foreign_data.out
+++ b/src/test/regress/expected/foreign_data.out
@@ -748,10 +748,62 @@ ERROR:  foreign-data wrapper "dummy" has no handler
 CREATE TABLE lt1 (a INT) PARTITION BY RANGE (a);
 CREATE FOREIGN TABLE ft_part1
   PARTITION OF lt1 FOR VALUES FROM (0) TO (1000) SERVER s0;
-CREATE INDEX ON lt1 (a);                                        -- ERROR
-ERROR:  cannot create index on partitioned table "lt1"
+CREATE INDEX ON lt1 (a);                              -- skips partition
+CREATE UNIQUE INDEX ON lt1 (a);                                 -- ERROR
+ERROR:  cannot create unique index on partitioned table "lt1"
 DETAIL:  Table "lt1" contains partitions that are foreign tables.
+ALTER TABLE lt1 ADD PRIMARY KEY (a);                            -- ERROR
+ERROR:  cannot create unique index on partitioned table "lt1"
+DETAIL:  Table "lt1" contains partitions that are foreign tables.
+DROP TABLE lt1;
+CREATE TABLE lt1 (a INT) PARTITION BY RANGE (a);
+CREATE INDEX ON lt1 (a);
+CREATE FOREIGN TABLE ft_part1
+  PARTITION OF lt1 FOR VALUES FROM (0) TO (1000) SERVER s0;
+CREATE FOREIGN TABLE ft_part2 (a INT) SERVER s0;
+ALTER TABLE lt1 ATTACH PARTITION ft_part2 FOR VALUES FROM (1000) TO (2000);
+DROP FOREIGN TABLE ft_part1, ft_part2;
+CREATE UNIQUE INDEX ON lt1 (a);
+ALTER TABLE lt1 ADD PRIMARY KEY (a);
+CREATE FOREIGN TABLE ft_part1
+  PARTITION OF lt1 FOR VALUES FROM (0) TO (1000) SERVER s0;     -- ERROR
+ERROR:  cannot create foreign partition of partitioned table "lt1"
+DETAIL:  Table "lt1" contains indexes that are unique.
+CREATE FOREIGN TABLE ft_part2 (a INT NOT NULL) SERVER s0;
+ALTER TABLE lt1 ATTACH PARTITION ft_part2
+  FOR VALUES FROM (1000) TO (2000);                             -- ERROR
+ERROR:  cannot attach foreign table "ft_part2" as partition of partitioned table "lt1"
+DETAIL:  Table "lt1" contains unique indexes.
+DROP TABLE lt1;
+DROP FOREIGN TABLE ft_part2;
+CREATE TABLE lt1 (a INT) PARTITION BY RANGE (a);
+CREATE INDEX ON lt1 (a);
+CREATE TABLE lt1_part1
+  PARTITION OF lt1 FOR VALUES FROM (0) TO (1000)
+  PARTITION BY RANGE (a);
+CREATE FOREIGN TABLE ft_part_1_1
+  PARTITION OF lt1_part1 FOR VALUES FROM (0) TO (100) SERVER s0;
+CREATE FOREIGN TABLE ft_part_1_2 (a INT) SERVER s0;
+ALTER TABLE lt1_part1 ATTACH PARTITION ft_part_1_2 FOR VALUES FROM (100) TO (200);
+CREATE UNIQUE INDEX ON lt1 (a);
+ERROR:  cannot create unique index on partitioned table "lt1"
+DETAIL:  Table "lt1" contains partitions that are foreign tables.
+ALTER TABLE lt1 ADD PRIMARY KEY (a);
+ERROR:  cannot create unique index on partitioned table "lt1_part1"
+DETAIL:  Table "lt1_part1" contains partitions that are foreign tables.
+DROP FOREIGN TABLE ft_part_1_1, ft_part_1_2;
+CREATE UNIQUE INDEX ON lt1 (a);
+ALTER TABLE lt1 ADD PRIMARY KEY (a);
+CREATE FOREIGN TABLE ft_part_1_1
+  PARTITION OF lt1_part1 FOR VALUES FROM (0) TO (100) SERVER s0;
+ERROR:  cannot create foreign partition of partitioned table "lt1_part1"
+DETAIL:  Table "lt1_part1" contains indexes that are unique.
+CREATE FOREIGN TABLE ft_part_1_2 (a INT NOT NULL) SERVER s0;
+ALTER TABLE lt1_part1 ATTACH PARTITION ft_part_1_2 FOR VALUES FROM (100) TO (200);
+ERROR:  cannot attach foreign table "ft_part_1_2" as partition of partitioned table "lt1_part1"
+DETAIL:  Table "lt1_part1" contains unique indexes.
 DROP TABLE lt1;
+DROP FOREIGN TABLE ft_part_1_2;
 -- ALTER FOREIGN TABLE
 COMMENT ON FOREIGN TABLE ft1 IS 'foreign table';
 COMMENT ON FOREIGN TABLE ft1 IS NULL;
diff --git a/src/test/regress/sql/foreign_data.sql b/src/test/regress/sql/foreign_data.sql
index c646ed91526..73f9f621d8f 100644
--- a/src/test/regress/sql/foreign_data.sql
+++ b/src/test/regress/sql/foreign_data.sql
@@ -318,9 +318,49 @@ EXPLAIN SELECT * FROM ft1;                                      -- ERROR
 CREATE TABLE lt1 (a INT) PARTITION BY RANGE (a);
 CREATE FOREIGN TABLE ft_part1
   PARTITION OF lt1 FOR VALUES FROM (0) TO (1000) SERVER s0;
-CREATE INDEX ON lt1 (a);                                        -- ERROR
+CREATE INDEX ON lt1 (a);                              -- skips partition
+CREATE UNIQUE INDEX ON lt1 (a);                                 -- ERROR
+ALTER TABLE lt1 ADD PRIMARY KEY (a);                            -- ERROR
 DROP TABLE lt1;
 
+CREATE TABLE lt1 (a INT) PARTITION BY RANGE (a);
+CREATE INDEX ON lt1 (a);
+CREATE FOREIGN TABLE ft_part1
+  PARTITION OF lt1 FOR VALUES FROM (0) TO (1000) SERVER s0;
+CREATE FOREIGN TABLE ft_part2 (a INT) SERVER s0;
+ALTER TABLE lt1 ATTACH PARTITION ft_part2 FOR VALUES FROM (1000) TO (2000);
+DROP FOREIGN TABLE ft_part1, ft_part2;
+CREATE UNIQUE INDEX ON lt1 (a);
+ALTER TABLE lt1 ADD PRIMARY KEY (a);
+CREATE FOREIGN TABLE ft_part1
+  PARTITION OF lt1 FOR VALUES FROM (0) TO (1000) SERVER s0;     -- ERROR
+CREATE FOREIGN TABLE ft_part2 (a INT NOT NULL) SERVER s0;
+ALTER TABLE lt1 ATTACH PARTITION ft_part2
+  FOR VALUES FROM (1000) TO (2000);                             -- ERROR
+DROP TABLE lt1;
+DROP FOREIGN TABLE ft_part2;
+
+CREATE TABLE lt1 (a INT) PARTITION BY RANGE (a);
+CREATE INDEX ON lt1 (a);
+CREATE TABLE lt1_part1
+  PARTITION OF lt1 FOR VALUES FROM (0) TO (1000)
+  PARTITION BY RANGE (a);
+CREATE FOREIGN TABLE ft_part_1_1
+  PARTITION OF lt1_part1 FOR VALUES FROM (0) TO (100) SERVER s0;
+CREATE FOREIGN TABLE ft_part_1_2 (a INT) SERVER s0;
+ALTER TABLE lt1_part1 ATTACH PARTITION ft_part_1_2 FOR VALUES FROM (100) TO (200);
+CREATE UNIQUE INDEX ON lt1 (a);
+ALTER TABLE lt1 ADD PRIMARY KEY (a);
+DROP FOREIGN TABLE ft_part_1_1, ft_part_1_2;
+CREATE UNIQUE INDEX ON lt1 (a);
+ALTER TABLE lt1 ADD PRIMARY KEY (a);
+CREATE FOREIGN TABLE ft_part_1_1
+  PARTITION OF lt1_part1 FOR VALUES FROM (0) TO (100) SERVER s0;
+CREATE FOREIGN TABLE ft_part_1_2 (a INT NOT NULL) SERVER s0;
+ALTER TABLE lt1_part1 ATTACH PARTITION ft_part_1_2 FOR VALUES FROM (100) TO (200);
+DROP TABLE lt1;
+DROP FOREIGN TABLE ft_part_1_2;
+
 -- ALTER FOREIGN TABLE
 COMMENT ON FOREIGN TABLE ft1 IS 'foreign table';
 COMMENT ON FOREIGN TABLE ft1 IS NULL;