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05d4cbf9b6
RelFileNumbers are now assigned using a separate counter, instead of being assigned from the OID counter. This counter never wraps around: if all 2^56 possible RelFileNumbers are used, an internal error occurs. As the cluster is limited to 2^64 total bytes of WAL, this limitation should not cause a problem in practice. If the counter were 64 bits wide rather than 56 bits wide, we would need to increase the width of the BufferTag, which might adversely impact buffer lookup performance. Also, this lets us use bigint for pg_class.relfilenode and other places where these values are exposed at the SQL level without worrying about overflow. This should remove the need to keep "tombstone" files around until the next checkpoint when relations are removed. We do that to keep RelFileNumbers from being recycled, but now that won't happen anyway. However, this patch doesn't actually change anything in this area; it just makes it possible for a future patch to do so. Dilip Kumar, based on an idea from Andres Freund, who also reviewed some earlier versions of the patch. Further review and some wordsmithing by me. Also reviewed at various points by Ashutosh Sharma, Vignesh C, Amul Sul, Álvaro Herrera, and Tom Lane. Discussion: http://postgr.es/m/CA+Tgmobp7+7kmi4gkq7Y+4AM9fTvL+O1oQ4-5gFTT+6Ng-dQ=g@mail.gmail.com
31 lines
1.1 KiB
SQL
31 lines
1.1 KiB
SQL
/* contrib/pg_buffercache/pg_buffercache--1.3--1.4.sql */
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-- complain if script is sourced in psql, rather than via ALTER EXTENSION
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\echo Use "ALTER EXTENSION pg_buffercache UPDATE TO '1.4'" to load this file. \quit
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/* First we have to remove them from the extension */
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ALTER EXTENSION pg_buffercache DROP VIEW pg_buffercache;
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ALTER EXTENSION pg_buffercache DROP FUNCTION pg_buffercache_pages();
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/* Then we can drop them */
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DROP VIEW pg_buffercache;
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DROP FUNCTION pg_buffercache_pages();
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/* Now redefine */
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CREATE FUNCTION pg_buffercache_pages()
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RETURNS SETOF RECORD
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AS 'MODULE_PATHNAME', 'pg_buffercache_pages_v1_4'
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LANGUAGE C PARALLEL SAFE;
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CREATE VIEW pg_buffercache AS
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SELECT P.* FROM pg_buffercache_pages() AS P
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(bufferid integer, relfilenode int8, reltablespace oid, reldatabase oid,
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relforknumber int2, relblocknumber int8, isdirty bool, usagecount int2,
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pinning_backends int4);
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-- Don't want these to be available to public.
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REVOKE ALL ON FUNCTION pg_buffercache_pages() FROM PUBLIC;
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REVOKE ALL ON pg_buffercache FROM PUBLIC;
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GRANT EXECUTE ON FUNCTION pg_buffercache_pages() TO pg_monitor;
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GRANT SELECT ON pg_buffercache TO pg_monitor;
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