Hi young, On Mon, 28 Aug 2017 15:33:46 +0800 "yang...@highgo.com" <yang...@highgo.com> wrote:
> Hello > > Looking at your hash partitioning syntax, I implemented a hash partition in a > more concise way, with no need to determine the number of sub-tables, and > dynamically add partitions. I think it is great work, but the current consensus about hash-partitioning supports Amul's patch[1], in which the syntax is different from the my original proposal. So, you will have to read Amul's patch and make a discussion if you still want to propose your implementation. Regards, [1] https://www.postgresql.org/message-id/CAAJ_b965A2oog=6efuhelexl3rmgfssb3g7lwkva1bw0wuj...@mail.gmail.com > > Description > > The hash partition's implement is on the basis of the original range / list > partition,and using similar syntax. > > To create a partitioned table ,use: > > CREATE TABLE h (id int) PARTITION BY HASH(id); > > The partitioning key supports only one value, and I think the partition key > can support multiple values, > which may be difficult to implement when querying, but it is not impossible. > > A partition table can be create as bellow: > > CREATE TABLE h1 PARTITION OF h; > CREATE TABLE h2 PARTITION OF h; > CREATE TABLE h3 PARTITION OF h; > > FOR VALUES clause cannot be used, and the partition bound is calclulated > automatically as partition index of single integer value. > > An inserted record is stored in a partition whose index equals > DatumGetUInt32(OidFunctionCall1(lookup_type_cache(key->parttypid[0], > TYPECACHE_HASH_PROC)->hash_proc, values[0])) % nparts/* Number of partitions > */ > ; > In the above example, this is > DatumGetUInt32(OidFunctionCall1(lookup_type_cache(key->parttypid[0], > TYPECACHE_HASH_PROC)->hash_proc, id)) % 3; > > postgres=# insert into h select generate_series(1,20); > INSERT 0 20 > postgres=# select tableoid::regclass,* from h; > tableoid | id > ----------+---- > h1 | 3 > h1 | 5 > h1 | 17 > h1 | 19 > h2 | 2 > h2 | 6 > h2 | 7 > h2 | 11 > h2 | 12 > h2 | 14 > h2 | 15 > h2 | 18 > h2 | 20 > h3 | 1 > h3 | 4 > h3 | 8 > h3 | 9 > h3 | 10 > h3 | 13 > h3 | 16 > (20 rows) > > The number of partitions here can be dynamically added, and if a new > partition is created, the number of partitions changes, the calculated target > partitions will change, and the same data is not reasonable in different > partitions,So you need to re-calculate the existing data and insert the > target partition when you create a new partition. > > postgres=# create table h4 partition of h; > CREATE TABLE > postgres=# select tableoid::regclass,* from h; > tableoid | id > ----------+---- > h1 | 5 > h1 | 17 > h1 | 19 > h1 | 6 > h1 | 12 > h1 | 8 > h1 | 13 > h2 | 11 > h2 | 14 > h3 | 1 > h3 | 9 > h3 | 2 > h3 | 15 > h4 | 3 > h4 | 7 > h4 | 18 > h4 | 20 > h4 | 4 > h4 | 10 > h4 | 16 > (20 rows) > > When querying the data, the hash partition uses the same algorithm as the > insertion, and filters out the table that does not need to be scanned. > > postgres=# explain analyze select * from h where id = 1; > QUERY PLAN > > ---------------------------------------------------------------------------------------------------- > Append (cost=0.00..41.88 rows=13 width=4) (actual time=0.020..0.023 rows=1 > loops=1) > -> Seq Scan on h3 (cost=0.00..41.88 rows=13 width=4) (actual > time=0.013..0.016 rows=1 loops=1) > Filter: (id = 1) > Rows Removed by Filter: 3 > Planning time: 0.346 ms > Execution time: 0.061 ms > (6 rows) > > postgres=# explain analyze select * from h where id in (1,5);; > QUERY PLAN > > ---------------------------------------------------------------------------------------------------- > Append (cost=0.00..83.75 rows=52 width=4) (actual time=0.016..0.028 rows=2 > loops=1) > -> Seq Scan on h1 (cost=0.00..41.88 rows=26 width=4) (actual > time=0.015..0.018 rows=1 loops=1) > Filter: (id = ANY ('{1,5}'::integer[])) > Rows Removed by Filter: 6 > -> Seq Scan on h3 (cost=0.00..41.88 rows=26 width=4) (actual > time=0.005..0.007 rows=1 loops=1) > Filter: (id = ANY ('{1,5}'::integer[])) > Rows Removed by Filter: 3 > Planning time: 0.720 ms > Execution time: 0.074 ms > (9 rows) > > postgres=# explain analyze select * from h where id = 1 or id = 5;; > QUERY PLAN > > ---------------------------------------------------------------------------------------------------- > Append (cost=0.00..96.50 rows=50 width=4) (actual time=0.017..0.078 rows=2 > loops=1) > -> Seq Scan on h1 (cost=0.00..48.25 rows=25 width=4) (actual > time=0.015..0.019 rows=1 loops=1) > Filter: ((id = 1) OR (id = 5)) > Rows Removed by Filter: 6 > -> Seq Scan on h3 (cost=0.00..48.25 rows=25 width=4) (actual > time=0.005..0.010 rows=1 loops=1) > Filter: ((id = 1) OR (id = 5)) > Rows Removed by Filter: 3 > Planning time: 0.396 ms > Execution time: 0.139 ms > (9 rows) > > Can not detach / attach / drop partition table. > > Best regards, > young > > > yonj1e.github.io > yang...@highgo.com -- Yugo Nagata <nag...@sraoss.co.jp> -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
