![]() This form sets the storage mode for a column. For more information on the use of statistics by the PostgreSQL query planner, refer to Section 14.2.Ĭhanging per-attribute options acquires a SHARE UPDATE EXCLUSIVE lock. Specify a value of 0 to revert to estimating the number of distinct values normally. ![]() This can be useful when the size of the table changes over time, since the multiplication by the number of rows in the table is not performed until query planning time. ![]() For example, a value of -1 implies that all values in the column are distinct, while a value of -0.5 implies that each value appears twice on the average. When set to a negative value, which must be greater than or equal to -1, ANALYZE will assume that the number of distinct nonnull values in the column is linear in the size of the table the exact count is to be computed by multiplying the estimated table size by the absolute value of the given number. When set to a positive value, ANALYZE will assume that the column contains exactly the specified number of distinct nonnull values. n_distinct affects the statistics for the table itself, while n_distinct_inherited affects the statistics gathered for the table plus its inheritance children. Currently, the only defined per-attribute options are n_distinct and n_distinct_inherited, which override the number-of-distinct-values estimates made by subsequent ANALYZE operations. This form sets or resets per-attribute options. SET STATISTICS acquires a SHARE UPDATE EXCLUSIVE lock. For more information on the use of statistics by the PostgreSQL query planner, refer to Section 14.2. The target can be set in the range 0 to 10000 alternatively, set it to -1 to revert to using the system default statistics target ( default_statistics_target). This form sets the per-column statistics-gathering target for subsequent ANALYZE operations. sequence_option is an option supported by ALTER SEQUENCE such as INCREMENT BY. These forms alter the sequence that underlies an existing identity column. If DROP IDENTITY IF EXISTS is specified and the column is not an identity column, no error is thrown. These forms change whether a column is an identity column or change the generation attribute of an existing identity column. RENAME CONSTRAINT constraint_name TO new_constraint_nameĪLTER TABLE ALL IN TABLESPACE name ]ĪTTACH PARTITION partition_name AS IDENTITY Set up trigger or cron so that new partitions get created and function gets updated to assign new data to correct partition.ALTER TABLE name ![]() Re-enable UPDATES and INSERTS on production database Set constraint exclusion to ON SET constraint_exclusion = on CREATE TABLE child_2014 (ĬONSTRAINT ck_2014 CHECK ( dt_created = DATE '' AND dt_created = ''::date AND dt_created = DATE '' ANDĪdd trigger so that function is called on INSERTS CREATE TRIGGER tr_insert BEFORE INSERT ON old_masterįOR EACH ROW EXECUTE PROCEDURE fn_insert() CREATE TABLE new_master (ĭt_created DATE DEFAULT CURRENT_DATE NOT NULLĬreate children that inherit from master. Here are the steps to do it:Ĭreate new master table. ![]() This prevents disruptions to the original table while it is actively in use and if there are any issues, I can easily delete the new master without issue and continue using the original table. Since #1 requires copying data from the master to the child while it is in an active production environment, I personally went with #2 (creating a new master). ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |