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Infinite bounds
Dmitry Ivanov edited this page Aug 24, 2017
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8 revisions
Release 1.3 introduced support for semi-infinite partition bounds, e.g. (-inf, 10) or (-100, +inf). NULL value of a corresponding type is used to specify infinite range bounds.
/* case #1 - 100% manual partition creation */
create table test_1 (val int8 not null);
select add_to_pathman_config('test_1', 'val', NULL); /* don't set default interval */
/* case #2 - 95% manual (auto naming) */
create table test_2 (val int8 not null);
select create_naming_sequence('test_2');
select add_to_pathman_config('test_2', 'val', '1000'); /* use default interval 1000 */
select add_range_partition('test_2', 1, 100); /* initial partition [1, 100) */
/* case #3 - create some partitions */
create table test_3 (val int8 not null);
select create_range_partitions('test_3', 'val', 1, 1000, 10);As we can see, table test_1 has no partitions yet:
table pathman_partition_list;
parent | partition | parttype | expr | range_min | range_max
--------+-----------+----------+------+-----------+-----------
test_2 | test_2_1 | 2 | val | 1 | 100
test_3 | test_3_1 | 2 | val | 1 | 1001
test_3 | test_3_2 | 2 | val | 1001 | 2001
test_3 | test_3_3 | 2 | val | 2001 | 3001
test_3 | test_3_4 | 2 | val | 3001 | 4001
test_3 | test_3_5 | 2 | val | 4001 | 5001
test_3 | test_3_6 | 2 | val | 5001 | 6001
test_3 | test_3_7 | 2 | val | 6001 | 7001
test_3 | test_3_8 | 2 | val | 7001 | 8001
test_3 | test_3_9 | 2 | val | 8001 | 9001
test_3 | test_3_10 | 2 | val | 9001 | 10001
(11 rows)Let's create a semi-infinite partition test_1_minus_inf:
select add_range_partition('test_1', NULL, 1, 'test_1_minus_inf');
add_range_partition
---------------------
test_1_minus_inf
(1 row)As we can see, its left bound is NULL:
select * from pathman_partition_list where parent = 'test_1'::regclass;
parent | partition | parttype | expr | range_min | range_max
--------+------------------+----------+------+-----------+-----------
test_1 | test_1_minus_inf | 2 | val | | 1
(1 row)
select range_min is null from pathman_partition_list
where parent = 'test_1'::regclass;
?column?
----------
t
(1 row)We can insert some data into it:
insert into test_1 values (0), (-10), (-100), (-1000) returning *, tableoid::regclass;
val | tableoid
-------+------------------
0 | test_1_minus_inf
-10 | test_1_minus_inf
-100 | test_1_minus_inf
-1000 | test_1_minus_inf
(4 rows)
INSERT 0 4Good, the data was successfully forwarded to the partition test_1_inf! Let's completely cover the range with a new partition test_1_plus_inf:
select add_range_partition('test_1', 1, NULL, 'test_1_plus_inf');
add_range_partition
---------------------
test_1_plus_inf
(1 row)Add a few more rows:
insert into test_1
select random() * 10000 - 5000 from generate_series(1, 6)
returning *, tableoid::regclass;
val | tableoid
-------+------------------
4525 | test_1_plus_inf
4912 | test_1_plus_inf
-1878 | test_1_minus_inf
-718 | test_1_minus_inf
2114 | test_1_plus_inf
2915 | test_1_plus_inf
(6 rows)
INSERT 0 6Note that we cannot append or prepend new partitions to table test_1:
select append_range_partition('test_1');
ERROR: Cannot append partition because last partition's range is half open
select prepend_range_partition('test_1');
ERROR: Cannot prepend partition because first partition's range is half openWe can also add semi-infinite partitions to an existing set of finite children that we've created beforehand:
/* add new partition [100, +inf) */
select add_range_partition('test_2', 100, NULL);
add_range_partition
---------------------
test_2_2
/* prepend will still work! */
select prepend_range_partition('test_2');
prepend_range_partition
-------------------------
test_2_3
(1 row)
/* check the partitions of table 'test_2' */
select * from pathman_partition_list where parent = 'test_2'::regclass;
parent | partition | parttype | expr | range_min | range_max
--------+-----------+----------+------+-----------+-----------
test_2 | test_2_3 | 2 | val | -999 | 1
test_2 | test_2_1 | 2 | val | 1 | 100
test_2 | test_2_2 | 2 | val | 100 |
(3 rows)All semi-infinite partitions are 1st class citizens, which means that operations like merge, split, drop will work as expected:
select merge_range_partitions('test_2_1', 'test_2_2');
merge_range_partitions
------------------------
(1 row)
select * from pathman_partition_list where parent = 'test_2'::regclass;
parent | partition | parttype | expr | range_min | range_max
--------+-----------+----------+------+-----------+-----------
test_2 | test_2_3 | 2 | val | -999 | 1
test_2 | test_2_1 | 2 | val | 1 |
(2 rows)
select split_range_partition('test_2_1', 2000);
split_range_partition
-----------------------
{1,NULL}
(1 row)
select * from pathman_partition_list where parent = 'test_2'::regclass;
parent | partition | parttype | expr | range_min | range_max
--------+-----------+----------+------+-----------+-----------
test_2 | test_2_3 | 2 | val | -999 | 1
test_2 | test_2_1 | 2 | val | 1 | 2000
test_2 | test_2_4 | 2 | val | 2000 |
(3 rows)
select drop_range_partition('test_2_4');
drop_range_partition
----------------------
test_2_4
(1 row)
select * from pathman_partition_list where parent = 'test_2'::regclass;
parent | partition | parttype | expr | range_min | range_max
--------+-----------+----------+------+-----------+-----------
test_2 | test_2_3 | 2 | val | -999 | 1
test_2 | test_2_1 | 2 | val | 1 | 2000
(2 rows)- Infinite bounds can only be used with RANGE partitioning;
- Only one bound (left or right) of a partition may be infinite (i.e.
(NULL, NULL)is prohibited);