我正在使用 Django ORM 和 postgresql。
ORM 创建一个查询：
SELECT
(date_part('month', stat_date)) AS "stat_date",
"direct_keywordstat"."banner_id",
SUM("direct_keywordstat"."total") AS "total",
SUM("direct_keywordstat"."clicks") AS "clicks",
SUM("direct_keywordstat"."shows") AS "shows"
FROM "direct_keywordstat"
LEFT OUTER JOIN "direct_banner" ON ("direct_keywordstat"."banner_id" = "direct_banner"."banner_ptr_id")
LEFT OUTER JOIN "platforms_banner" ON ("direct_banner"."banner_ptr_id" = "platforms_banner"."id")
WHERE (
"direct_keywordstat".stat_date BETWEEN E'2009-08-25' AND E'2010-08-25' AND
"direct_keywordstat"."keyword_id" IN (
SELECT U0."id"
FROM "direct_keyword" U0
INNER JOIN "direct_banner" U1 ON (U0."banner_id" = U1."banner_ptr_id")
INNER JOIN "platforms_banner" U2 ON (U1."banner_ptr_id" = U2."id")
INNER JOIN "platforms_campaign" U3 ON (U2."campaign_id" = U3."id")
INNER JOIN "direct_campaign" U4 ON (U3."id" = U4."campaign_ptr_id")
WHERE (
U0."deleted" = E'False' AND
U0."low_ctr" = E'False' AND
U4."status_active" = E'True' AND
U0."banner_id" IN (
SELECT U0."banner_ptr_id"
FROM "direct_banner" U0
INNER JOIN "platforms_banner" U1
ON (U0."banner_ptr_id" = U1."id")
WHERE (
U0."status_show" = E'True' AND
U1."campaign_id" = E'174' )
)
)
)
)
GROUP BY
"direct_keywordstat"."banner_id",
(date_part('month', stat_date)),
"platforms_banner"."title", date_trunc('month', stat_date)
ORDER BY "platforms_banner"."title" ASC, "stat_date" ASC
问题是，direct_keywordstat 包含 300 万+条记录，因此查询在大约 15 秒内执行。
我试过创建像这样的索引
CREATE INDEX direct_keywordstat_stat_date on direct_keywordstat using btree(stat_date);
但是 EXPLAIN ANALYZE 显示没有使用索引。
表架构：
\d direct_keywordstat
Table "public.direct_keywordstat"
Column | Type | Modifiers
-------------+------------------------+-----------------------------------------------------------------
id | integer | not null default nextval('direct_keywordstat_id_seq'::regclass)
keyword_id | integer | not null
banner_id | integer | not null
campaign_id | integer | not null
stat_date | date | not null
region_id | integer | not null
place_type | character varying(30) |
place_name | character varying(100) |
clicks | integer | not null default 0
shows | integer | not null default 0
total | numeric(19,6) | not null
如何创建有用的索引？
或者，也许，有机会以其他方式优化此查询？
事情是，如果 WHERE 看起来像
"direct_keywordstat".clicks BETWEEN 10 AND 3000000
查询在 0.8 秒内执行。