Tim Abbott 4d94d4d6f6 [schema] Add case-insensitive index on message subject field. ...

We need to run the schema migration manually using

"CREATE INDEX CONCURRENTLY upper_subject_idx ON zerver_message ((upper(subject)));"

since we need CONCURRENTLY and I seem to recall that doesn't work with South.

Apparently our existing indexes on subject/topic weren't being used in
our narrowing queries, because we do case-insensitive search.

This substantially improves our database performance around
stream+topic narrows.  See before and after query plans below from my
test instance.

humbug=# explain analyze SELECT "zerver_message"."id" FROM "zerver_message" WHERE ("zerver_message"."recipient_id" = 38  AND UPPER(zerver_message.subject) = 'TEST'  AND "zerver_message"."id" <= 348495 ) ORDER BY "zerver_message"."id" DESC LIMIT 50;
                                                                       QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=13510.61..13510.71 rows=41 width=4) (actual time=32.952..32.958 rows=2 loops=1)
   ->  Sort  (cost=13510.61..13510.71 rows=41 width=4) (actual time=32.946..32.947 rows=2 loops=1)
         Sort Key: id
         Sort Method: quicksort  Memory: 25kB
         ->  Bitmap Heap Scan on zerver_message  (cost=237.99..13509.51 rows=41 width=4) (actual time=2.357..32.912 rows=2 loops=1)
               Recheck Cond: (recipient_id = 38)
               Filter: ((id <= 348495) AND (upper((subject)::text) = 'TEST'::text))
               ->  Bitmap Index Scan on zephyr_message_recipient_id  (cost=0.00..237.98 rows=8221 width=0) (actual time=1.178..1.178 rows=10354 loops=1)
                     Index Cond: (recipient_id = 38)
 Total runtime: 33.049 ms
(10 rows)

humbug=# explain analyze SELECT "zerver_message"."id" FROM "zerver_message" WHERE ("zerver_message"."recipient_id" = 38  AND UPPER(zerver_message.subject) = 'TEST'  AND "zerver_message"."id" <= 348495 ) ORDER BY "zerver_message"."id" DESC LIMIT 50;
                                                                          QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=435.11..435.22 rows=41 width=4) (actual time=4.998..4.999 rows=2 loops=1)
   ->  Sort  (cost=435.11..435.22 rows=41 width=4) (actual time=4.997..4.997 rows=2 loops=1)
         Sort Key: id
         Sort Method: quicksort  Memory: 25kB
         ->  Bitmap Heap Scan on zerver_message  (cost=275.63..434.02 rows=41 width=4) (actual time=4.981..4.984 rows=2 loops=1)
               Recheck Cond: ((upper((subject)::text) = 'TEST'::text) AND (recipient_id = 38))
               Filter: (id <= 348495)
               ->  BitmapAnd  (cost=275.63..275.63 rows=41 width=0) (actual time=4.954..4.954 rows=0 loops=1)
                     ->  Bitmap Index Scan on upper_subject_idx  (cost=0.00..37.38 rows=1744 width=0) (actual time=2.972..2.972 rows=27457 loops=1)
                           Index Cond: (upper((subject)::text) = 'TEST'::text)
                     ->  Bitmap Index Scan on zephyr_message_recipient_id  (cost=0.00..237.98 rows=8221 width=0) (actual time=0.855..0.855 rows=10354 loops=1)
                           Index Cond: (recipient_id = 38)
 Total runtime: 5.049 ms
(13 rows)

(imported from commit 1f4815ccb0691053ff8d505149482dbc74153fb3)

2013-10-18 16:38:31 -04:00

16 KiB

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