> I don't *think* we are using SSDs but I'll need to confirm that though. Confirmed we are not using SSDs but '10K RPM SAS in RAID-10.' I've also been hunt for other queries that show this behaviour too, and I've found one. The PG settings/versions will be different in this example due to the earlier example being for our internal CI/CD tool which is hosted a on local instance of PG. This example is directly from our production servers. Query C (slow):- SELECT COUNT(1) FROM proposal.proposal INNER JOIN proposal.note ON proposal.note.proposal_reference = proposal.proposal.reference WHERE 1 = 1 AND proposal.proposal.system_id = 11 AND proposal.proposal.legacy_organisation_id IN (6, 7, 11, 16, 18, 44, 200, 218, 233, 237, 259, 47) AND proposal.proposal.has_been_anonymised = false AND proposal.note.legacy_read_by IS NULL AND proposal.note.type_id IN (1, 4, 9) AND proposal.note.entry_time > '2020-04-01' AND proposal.note.entry_time < '2020-05-01'; Query D (fast):- SELECT COUNT(1) FROM proposal.proposal INNER JOIN proposal.note ON proposal.note.proposal_reference = proposal.proposal.reference WHERE 1 = 1 AND proposal.proposal.system_id = 11 AND proposal.proposal.legacy_organisation_id IN (6, 7, 11, 16, 18, 44, 200, 218, 233, 237, 259, 47) AND proposal.proposal.has_been_anonymised = false AND proposal.proposal.has_been_anonymised = false AND proposal.note.legacy_read_by IS NULL AND proposal.note.type_id IN (1, 4, 9) AND proposal.note.entry_time > '2020-04-01' AND proposal.note.entry_time < '2020-05-01'; The EXPLAIN ANALYZE for both queries can be found here:- Query C: https://explain.depesz.com/s/5Mbu Query D: https://explain.depesz.com/s/jVnH The table definitions (including the indexes) can be found here:- proposal.proposal: https://gist.github.com/indy-singh/6ccd86ff859e7cdad2ec1bf73a61445c proposal.note: https://gist.github.com/indy-singh/6c1f85ad15cb92e138447a91d8cf3ecb Data stats:- proposal.proposal has 10,324,779 rows and once the table specific conditions are applied there are 39,223 rows left. proposal.note has 28,97,698 rows and once the table specific conditions are applied there are 54,359 rows left. PG version: PostgreSQL 9.5.17 on x86_64-pc-linux-gnu (Debian 9.5.17-1.pgdg90+1), compiled by gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516, 64-bit -- SELECT relname, relpages, reltuples, relallvisible, relkind, relnatts, relhassubclass, reloptions, pg_table_size(oid) FROM pg_class WHERE relname='TABLE_NAME' Table metadata:- proposal.proposal: https://gist.github.com/indy-singh/24e7ec8f3d4e2c3ac73f724cea52f9de proposal.note: https://gist.github.com/indy-singh/104d6ec7ef8179461eb4f91c121615e0 Index Stats:- proposal.proposal: https://gist.github.com/indy-singh/1d41d15addb543bcdafc8641b9d7f036 proposal.note: https://gist.github.com/indy-singh/7a698dec98dd8ef2808345d1802e6b6a Last Vacuum:- proposal.proposal: Never proposal.note: 2020-04-17 15:10:57.256013+01 Last Analyze: proposal.proposal: Never proposal.note: 2020-04-07 11:48:49.689622+01 Server Configuration: https://gist.github.com/indy-singh/b19134873f266ee6ce2b9815504d130c Indy
