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Make attstattarget nullable

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This changes the pg_attribute field attstattarget into a nullable
field in the variable-length part of the row.  If no value is set by
the user for attstattarget, it is now null instead of previously -1.
This saves space in pg_attribute and tuple descriptors for most
practical scenarios.  (ATTRIBUTE_FIXED_PART_SIZE is reduced from 108
to 104.)  Also, null is the semantically more correct value.

The ANALYZE code internally continues to represent the default
statistics target by -1, so that that code can avoid having to deal
with null values.  But that is now contained to the ANALYZE code.
Only the DDL code deals with attstattarget possibly null.

For system columns, the field is now always null.  The ANALYZE code
skips system columns anyway.

To set a column's statistics target to the default value, the new
command form ALTER TABLE ... SET STATISTICS DEFAULT can be used.  (SET
STATISTICS -1 still works.)

Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://www.postgresql.org/message-id/flat/4da8d211-d54d-44b9-9847-f2a9f1184c76@eisentraut.org
This commit is contained in:
Peter Eisentraut
2024-01-13 18:14:53 +01:00
parent 45da69371e
commit 4f622503d6
16 changed files with 115 additions and 89 deletions
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18
src/backend/parser/gram.y
View File

@@ -337,6 +337,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
%type <list> alter_table_cmds alter_type_cmds
%type <list> alter_identity_column_option_list
%type <defelt> alter_identity_column_option
%type <node> set_statistics_value
%type <list> createdb_opt_list createdb_opt_items copy_opt_list
transaction_mode_list
@@ -2446,18 +2447,18 @@ alter_table_cmd:
n->missing_ok = true;
$$ = (Node *) n;
}
/* ALTER TABLE <name> ALTER [COLUMN] <colname> SET STATISTICS <SignedIconst> */
| ALTER opt_column ColId SET STATISTICS SignedIconst
/* ALTER TABLE <name> ALTER [COLUMN] <colname> SET STATISTICS */
| ALTER opt_column ColId SET STATISTICS set_statistics_value
{
AlterTableCmd *n = makeNode(AlterTableCmd);
n->subtype = AT_SetStatistics;
n->name = $3;
n->def = (Node *) makeInteger($6);
n->def = $6;
$$ = (Node *) n;
}
/* ALTER TABLE <name> ALTER [COLUMN] <colnum> SET STATISTICS <SignedIconst> */
| ALTER opt_column Iconst SET STATISTICS SignedIconst
/* ALTER TABLE <name> ALTER [COLUMN] <colnum> SET STATISTICS */
| ALTER opt_column Iconst SET STATISTICS set_statistics_value
{
AlterTableCmd *n = makeNode(AlterTableCmd);
@@ -2469,7 +2470,7 @@ alter_table_cmd:
n->subtype = AT_SetStatistics;
n->num = (int16) $3;
n->def = (Node *) makeInteger($6);
n->def = $6;
$$ = (Node *) n;
}
/* ALTER TABLE <name> ALTER [COLUMN] <colname> SET ( column_parameter = value [, ... ] ) */
@@ -3070,6 +3071,11 @@ alter_identity_column_option:
}
;
set_statistics_value:
SignedIconst { $$ = (Node *) makeInteger($1); }
| DEFAULT { $$ = NULL; }
;
PartitionBoundSpec:
/* a HASH partition */
FOR VALUES WITH '(' hash_partbound ')'