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

2 files changed, 43 insertions, 0 deletions

diff --git a/src/test/regress/expected/partition_merge.out b/src/test/regress/expected/partition_merge.out
index 373d32948ca..2e0bfdc705d 100644
--- 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 6a0b35b1799..72b1cb0b35e 100644
--- a/src/test/regress/sql/partition_merge.sql
+++ b/src/test/regress/sql/partition_merge.sql
@@ -445,4 +445,22 @@ 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;