Don't copy extended statistics during MERGE/SPLIT partition operations

When MERGE/SPLIT created new partitions, it was cloning the extended statistics of the parent table. However, extended stats on partitioned tables don't behave like indexes on partitioned tables (which exist only to create physical indexes on child tables). Rather, extended stats on a parent 1) cause extended stats to be collected and computed across the whole partition hierarchy, and 2) do not cause extended stats to be computed for the individual partitions. "CREATE TABLE ... PARTITION OF" command doesn't copy extended statistics. This commit makes createPartitionTable() behave consistently. Reported-by: Justin Pryzby Discussion: https://postgr.es/m/ZiJW1g2nbQs9ekwK%40pryzbyj2023 Author: Alexander Korotkov, Justin Pryzby

Author: akorotkov

doc/src/sgml/ref/alter_table.sgml

@@ -1154,9 +1154,12 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
  </para>
  <para>
  The new partitions will be created the same as tables created with the
- SQL command <literal>CREATE TABLE <replaceable class="parameter">partition_nameN</replaceable> (LIKE <replaceable class="parameter">name</replaceable> INCLUDING ALL EXCLUDING INDEXES EXCLUDING IDENTITY)</literal>.
+ SQL command <literal>CREATE TABLE <replaceable class="parameter">partition_nameN</replaceable> (LIKE <replaceable class="parameter">name</replaceable> INCLUDING ALL EXCLUDING INDEXES EXCLUDING IDENTITY EXCLUDING STATISTICS)</literal>.
  The indexes and identity are created later, after moving the data
  into the new partitions.
+ Extended statistics aren't copied from the parent table, for consistency with
+ <command>CREATE TABLE PARTITION OF</command>.
+
  New partitions will have the same table access method as the parent.
  If the parent table is persistent then new partitions are created
  persistent. If the parent table is temporary then new partitions
@@ -1224,9 +1227,11 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
  </para>
  <para>
  The new partition will be created the same as a table created with the
- SQL command <literal>CREATE TABLE <replaceable class="parameter">partition_name</replaceable> (LIKE <replaceable class="parameter">name</replaceable> INCLUDING ALL EXCLUDING INDEXES EXCLUDING IDENTITY)</literal>.
+ SQL command <literal>CREATE TABLE <replaceable class="parameter">partition_name</replaceable> (LIKE <replaceable class="parameter">name</replaceable> INCLUDING ALL EXCLUDING INDEXES EXCLUDING IDENTITY EXCLUDING STATISTICS)</literal>.
  The indexes and identity are created later, after moving the data
  into the new partition.
+ Extended statistics aren't copied from the parent table, for consistency with
+ <command>CREATE TABLE PARTITION OF</command>.
  The new partition will have the same table access method as the parent.
  If the parent table is persistent then the new partition is created
  persistent. If the parent table is temporary then the new partition

src/backend/commands/tablecmds.c

@@ -20269,7 +20269,7 @@ moveSplitTableRows(Relation rel, Relation splitRel, List *partlist, List *newPar
  * (newPartName) like table (modelRel)
  *
  * Emulates command: CREATE [TEMP] TABLE <newPartName> (LIKE <modelRel's name>
- * INCLUDING ALL EXCLUDING INDEXES EXCLUDING IDENTITY)
+ * INCLUDING ALL EXCLUDING INDEXES EXCLUDING IDENTITY EXCLUDING STATISTICS)
  *
  * Also, this function sets the new partition access method same as parent
  * table access methods (similarly to CREATE TABLE ... PARTITION OF). It
@@ -20313,9 +20313,11 @@ createPartitionTable(RangeVar *newPartName, Relation modelRel,
 
 /*
  * Indexes will be inherited on "attach new partitions" stage, after data
- * moving.
+ * moving. We also don't copy the extended statistics for consistency
+ * with CREATE TABLE PARTITION OF.
  */
-tlc->options = CREATE_TABLE_LIKE_ALL & ~(CREATE_TABLE_LIKE_INDEXES | CREATE_TABLE_LIKE_IDENTITY);
+tlc->options = CREATE_TABLE_LIKE_ALL &
+~(CREATE_TABLE_LIKE_INDEXES | CREATE_TABLE_LIKE_IDENTITY | CREATE_TABLE_LIKE_STATISTICS);
 tlc->relationOid = InvalidOid;
 createStmt->tableElts = lappend(createStmt->tableElts, tlc);