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4f622503d6
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