Change the way ATExecMergePartitions() handles the name collision

The name collision happens when the name of the new partition is the same as
the name of one of the merging partitions.  Currently, ATExecMergePartitions()
first gives the new partition a temporary name and then renames it when old
partitions are deleted.  That negatively influences the naming of related
objects like indexes and constrains, which could inherit a temporary name.

This commit changes the implementation in the following way.  A merging
partition gets renamed first, then the new partition is created with the
right name immediately.  This resolves the issue of the naming of related
objects.

Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/edfbd846-dcc1-42d1-ac26-715691b687d3%40postgrespro.ru
Author: Dmitry Koval, Alexander Korotkov
Reviewed-by: Robert Haas, Justin Pryzby, Pavel Borisov

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index f1725c9da8cdfc4f5fa71dbc0dc89c74a9d37401..8fa09afdc59a6e4c1bf4ef79eee738dc1dfc4a66 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -21503,9 +21503,6 @@ ATExecMergePartitions(List **wqueue, AlteredTableInfo *tab, Relation rel,
        ListCell   *listptr;
        List       *mergingPartitionsList = NIL;
        Oid                     defaultPartOid;
-       char            tmpRelName[NAMEDATALEN];
-       RangeVar   *mergePartName = cmd->name;
-       bool            isSameName = false;
 
        /*
         * Lock all merged partitions, check them and create list with partitions
@@ -21527,8 +21524,28 @@ ATExecMergePartitions(List **wqueue, AlteredTableInfo *tab, Relation rel,
                 * function transformPartitionCmdForMerge().
                 */
                if (equal(name, cmd->name))
+               {
                        /* One new partition can have the same name as merged partition. */
-                       isSameName = true;
+                       char            tmpRelName[NAMEDATALEN];
+
+                       /* Generate temporary name. */
+                       sprintf(tmpRelName, "merge-%u-%X-tmp", RelationGetRelid(rel), MyProcPid);
+
+                       /*
+                        * Rename the existing partition with a temporary name, leaving it
+                        * free for the new partition.  We don't need to care about this
+                        * in the future because we're going to eventually drop the
+                        * existing partition anyway.
+                        */
+                       RenameRelationInternal(RelationGetRelid(mergingPartition),
+                                                                  tmpRelName, false, false);
+
+                       /*
+                        * We must bump the command counter to make the new partition
+                        * tuple visible for rename.
+                        */
+                       CommandCounterIncrement();
+               }
 
                /* Store a next merging partition into the list. */
                mergingPartitionsList = lappend(mergingPartitionsList,
@@ -21548,15 +21565,7 @@ ATExecMergePartitions(List **wqueue, AlteredTableInfo *tab, Relation rel,
                DetachPartitionFinalize(rel, mergingPartition, false, defaultPartOid);
        }
 
-       /* Create table for new partition, use partitioned table as model. */
-       if (isSameName)
-       {
-               /* Create partition table with generated temporary name. */
-               sprintf(tmpRelName, "merge-%u-%X-tmp", RelationGetRelid(rel), MyProcPid);
-               mergePartName = makeRangeVar(get_namespace_name(RelationGetNamespace(rel)),
-                                                                        tmpRelName, -1);
-       }
-       createPartitionTable(mergePartName,
+       createPartitionTable(cmd->name,
                                                 makeRangeVar(get_namespace_name(RelationGetNamespace(rel)),
                                                                          RelationGetRelationName(rel), -1),
                                                 context);
@@ -21567,18 +21576,12 @@ ATExecMergePartitions(List **wqueue, AlteredTableInfo *tab, Relation rel,
         * excessive, but this is the way we make sure nobody is planning queries
         * involving merging partitions.
         */
-       newPartRel = table_openrv(mergePartName, AccessExclusiveLock);
+       newPartRel = table_openrv(cmd->name, AccessExclusiveLock);
 
        /* Copy data from merged partitions to new partition. */
        moveMergedTablesRows(rel, mergingPartitionsList, newPartRel);
 
-       /*
-        * Attach a new partition to the partitioned table. wqueue = NULL:
-        * verification for each cloned constraint is not need.
-        */
-       attachPartitionTable(NULL, rel, newPartRel, cmd->bound);
-
-       /* Unlock and drop merged partitions. */
+       /* Drop the current partitions before attaching the new one. */
        foreach(listptr, mergingPartitionsList)
        {
                ObjectAddress object;
@@ -21596,18 +21599,12 @@ ATExecMergePartitions(List **wqueue, AlteredTableInfo *tab, Relation rel,
        }
        list_free(mergingPartitionsList);
 
-       /* Rename new partition if it is needed. */
-       if (isSameName)
-       {
-               /*
-                * We must bump the command counter to make the new partition tuple
-                * visible for rename.
-                */
-               CommandCounterIncrement();
-               /* Rename partition. */
-               RenameRelationInternal(RelationGetRelid(newPartRel),
-                                                          cmd->name->relname, false, false);
-       }
+       /*
+        * Attach a new partition to the partitioned table. wqueue = NULL:
+        * verification for each cloned constraint is not needed.
+        */
+       attachPartitionTable(NULL, rel, newPartRel, cmd->bound);
+
        /* Keep the lock until commit. */
        table_close(newPartRel, NoLock);
 }

diff --git a/src/test/regress/expected/partition_merge.out b/src/test/regress/expected/partition_merge.out
index 373d32948cac2c2c7f54e3fea2ad7f79792b734c..2e0bfdc705d4971b4c49498dcd2289c1658a23a0 100644 (file)
--- a/src/test/regress/expected/partition_merge.out
+++ b/src/test/regress/expected/partition_merge.out
@@ -746,4 +746,29 @@ DROP TABLE t3;
 DROP TABLE t2;
 DROP TABLE t1;
 --
+-- Check the partition index name if the partition name is the same as one
+-- of the merged partitions.
+--
+CREATE TABLE t (i int, PRIMARY KEY(i)) PARTITION BY RANGE (i);
+CREATE TABLE tp_0_1 PARTITION OF t FOR VALUES FROM (0) TO (1);
+CREATE TABLE tp_1_2 PARTITION OF t FOR VALUES FROM (1) TO (2);
+CREATE INDEX tidx ON t(i);
+ALTER TABLE t MERGE PARTITIONS (tp_1_2, tp_0_1) INTO tp_1_2;
+-- Indexname values should be 'tp_1_2_pkey' and 'tp_1_2_i_idx'.
+-- Not-null constraint name should be 'tp_1_2_i_not_null'.
+\d+ tp_1_2
+                          Table "partitions_merge_schema.tp_1_2"
+ Column |  Type   | Collation | Nullable | Default | Storage | Stats target | Description 
+--------+---------+-----------+----------+---------+---------+--------------+-------------
+ i      | integer |           | not null |         | plain   |              | 
+Partition of: t FOR VALUES FROM (0) TO (2)
+Partition constraint: ((i IS NOT NULL) AND (i >= 0) AND (i < 2))
+Indexes:
+    "tp_1_2_pkey" PRIMARY KEY, btree (i)
+    "tp_1_2_i_idx" btree (i)
+Not-null constraints:
+    "tp_1_2_i_not_null" NOT NULL "i"
+
+DROP TABLE t;
+--
 DROP SCHEMA partitions_merge_schema;

diff --git a/src/test/regress/sql/partition_merge.sql b/src/test/regress/sql/partition_merge.sql
index 6a0b35b1799accb4067121dcbc8f8e2c5ee73eb0..72b1cb0b35e1d5512f9055f06df0646147b2a8ad 100644 (file)
--- a/src/test/regress/sql/partition_merge.sql
+++ b/src/test/regress/sql/partition_merge.sql
@@ -444,5 +444,23 @@ DROP TABLE t3;
 DROP TABLE t2;
 DROP TABLE t1;
 
+--
+-- Check the partition index name if the partition name is the same as one
+-- of the merged partitions.
+--
+CREATE TABLE t (i int, PRIMARY KEY(i)) PARTITION BY RANGE (i);
+
+CREATE TABLE tp_0_1 PARTITION OF t FOR VALUES FROM (0) TO (1);
+CREATE TABLE tp_1_2 PARTITION OF t FOR VALUES FROM (1) TO (2);
+
+CREATE INDEX tidx ON t(i);
+ALTER TABLE t MERGE PARTITIONS (tp_1_2, tp_0_1) INTO tp_1_2;
+
+-- Indexname values should be 'tp_1_2_pkey' and 'tp_1_2_i_idx'.
+-- Not-null constraint name should be 'tp_1_2_i_not_null'.
+\d+ tp_1_2
+
+DROP TABLE t;
+
 --
 DROP SCHEMA partitions_merge_schema;