Probably the cardinality of "vclf_number" is really bad. So the scan on that index is returning many million or billion rows and then you get a recheck which takes semi-forever. So you need an index on cl_value or both vclf_number and cl_value. If you know some properties of the values actually stored inside of those that will help.
Matthew Hall > On Jun 5, 2018, at 7:17 AM, Fred Habash <fmhab...@gmail.com> wrote: > > Trying to optimize the Elapsed Time (ET) of this query. Currently, it is > hovering around 3 hrs. > > Running a 'vaccum analyse' had no effect on ET. Even forcing an 'indexonly' > scan by disabling 'enable_seqscan', still around the 3 hrs. > The table is around 4.6B rows, > explain select cit_id, cl_value from reflink.citation_locators where > cl_value = '1507617681' and vclf_number = 1 ; > QUERY PLAN > > ----------------------------------------------------------------------------------------- > Bitmap Heap Scan on citation_locators (cost=5066559.01..50999084.79 > rows=133 width=23) > Recheck Cond: (vclf_number = 1) > Filter: (cl_value = '1507617681'::text) > -> Bitmap Index Scan on cl_indx_fk02 (cost=0.00..5066558.97 > rows=493984719 width=0) > Index Cond: (vclf_number = 1) > (5 rows) > > reflink.citation_locators > Table "reflink.citation_locators" > Column | Type | Modifiers | Storage | Stats > target | Description > ------------------+--------------------------+-----------+----------+--------------+------------- > cl_id | bigint | not null | plain | > | > cl_value | text | not null | extended | > | > vclf_number | integer | not null | plain | > | > cit_id | bigint | not null | plain | > | > cl_date_created | timestamp with time zone | not null | plain | > | > cl_date_modified | timestamp with time zone | | plain | > | > Indexes: > "cl_pk" PRIMARY KEY, btree (cl_id) > "cl_cnst_uk01" UNIQUE CONSTRAINT, btree (cit_id, vclf_number, cl_value) > "cl_indx_fk01" btree (cit_id) > "cl_indx_fk02" btree (vclf_number) > Foreign-key constraints: > "cl_cnst_fk01" FOREIGN KEY (cit_id) REFERENCES citations(cit_id) NOT > VALID "cl_cnst_fk02" FOREIGN KEY (vclf_number) REFERENCES > valid_cit_locator_fields(vclf_number)
