我有超过30秒的查询，看起来像这样
select
coalesce(sum("paidInstallment"-(plafond/tenor*frequency)),0)
from
account_transaction_debit atd
join r_account_transaction_debit ratd on atd.id = ratd."accountTransactionDebitId" and atd."deletedAt" isnull and ratd."deletedAt" isnulland atd."type" = 'INSTALLMENT'
join account a on a.id = ratd."accountId" and a."deletedAt" isnull and a.id = 4735
join r_account_transaction_debit_installment ratdi ratd."accountTransactionDebitId" = atd.id and ratdi."deletedAt" isnull
join installment i on i.id = ratdi."installmentId" and i."deletedAt" isnull
join r_loan_installment rli on i.id = rli."installmentId" rli."deletedAt" isnull
join loan l on l.id = rli."loanId" and l."deletedAt" isnull
where
atd."createdAt"::date between date_trunc('week',current_date) and current_date;
这是预期使用的索引（n.b。：＆＃34; createdAt＆＃34; type是带时区的时间戳）
CREATE UNIQUE INDEX
account_transaction_debit_deletedAt_type_createdAtDate_id_idx
ON account_transaction_debit ("deletedAt","type",my_to_char("createdAt"),id);
和my_to_char功能看起来像
CREATE OR REPLACE FUNCTION my_to_char(some_time timestamptz)
RETURNS text
AS
$BODY$
select to_char($1, 'yyyy-mm-dd');
$BODY$
LANGUAGE sql
IMMUTABLE;
最后解释（分析，详细，缓冲）结果
Aggregate (cost=17943983.42..17943983.43 rows=1 width=32) (actual time=3020772.135..3020772.135 rows=1 loops=1)
Output: COALESCE(sum((i."paidInstallment" - ((l.plafond / (l.tenor)::numeric) * (i.frequency)::numeric))), '0'::numeric)
Buffers: shared hit=84541, temp read=25220 written=25092
-> Nested Loop (cost=157262.23..8369328.64 rows=638310318 width=18) (actual time=3520.565..593472.501 rows=3168056628 loops=1)
Output: i."paidInstallment", l.plafond, l.tenor, i.frequency
Buffers: shared hit=84541, temp read=25220 written=25092
-> Nested Loop (cost=125695.82..280946.58 rows=1384621 width=22) (actual time=1266.622..6543.090 rows=1496484 loops=1)
Output: i."paidInstallment", i.frequency, l.plafond, l.tenor, a.id
Buffers: shared hit=53058, temp read=25012 written=24886
-> Index Scan using account_id_idx on public.account a (cost=0.29..8.31 rows=1 width=4) (actual time=0.012..0.518 rows=1 loops=1)
Output: a.id, a."totalDebit", a."totalCredit", a."totalBalance", a."createdAt", a."updatedAt", a."deletedAt", a."oldId", a.threshold
Index Cond: (a.id = 4735)
Filter: (a."deletedAt" IS NULL)
Buffers: shared hit=93
-> Hash Join (cost=125695.53..267092.07 rows=1384621 width=18) (actual time=1266.608..6240.859 rows=1496484 loops=1)
Output: i."paidInstallment", i.frequency, l.plafond, l.tenor
Hash Cond: (rli."loanId" = l.id)
Buffers: shared hit=52965, temp read=25012 written=24886
-> Hash Join (cost=120652.07..228476.25 rows=1434437 width=14) (actual time=1224.901..4429.943 rows=1496484 loops=1)
Output: i."paidInstallment", i.frequency, rli."loanId"
Hash Cond: (ratdi."installmentId" = i.id)
Buffers: shared hit=49833, temp read=21586 written=21462
-> Hash Join (cost=52321.11..118507.38 rows=1493212 width=12) (actual time=552.083..1704.683 rows=1496484 loops=1)
Output: ratdi."installmentId", rli."installmentId", rli."loanId"
Hash Cond: (ratdi."installmentId" = rli."installmentId")
Buffers: shared hit=21624, temp read=9403 written=9341
-> Seq Scan on public.r_account_transaction_debit_installment ratdi (cost=0.00..25809.68 rows=1511094 width=4) (actual time=0.010..303.506 rows=1496491 loops=1)
Output: ratdi."installmentId"
Filter: (ratdi."deletedAt" IS NULL)
Rows Removed by Filter: 8502
Buffers: shared hit=10606
-> Hash (cost=26774.97..26774.97 rows=1557051 width=8) (actual time=551.360..551.360 rows=1529141 loops=1)
Output: rli."installmentId", rli."loanId"
Buckets: 131072 Batches: 32 Memory Usage: 2897kB
Buffers: shared hit=11018, temp written=5047
-> Seq Scan on public.r_loan_installment rli (cost=0.00..26774.97 rows=1557051 width=8) (actual time=0.010..267.452 rows=1529141 loops=1)
Output: rli."installmentId", rli."loanId"
Filter: (rli."deletedAt" IS NULL)
Rows Removed by Filter: 17031
Buffers: shared hit=11018
-> Hash (cost=43020.87..43020.87 rows=1456007 width=14) (actual time=672.617..672.617 rows=1510902 loops=1)
Output: i."paidInstallment", i.frequency, i.id
Buckets: 131072 Batches: 32 Memory Usage: 3244kB
Buffers: shared hit=28209, temp written=6413
-> Seq Scan on public.installment i (cost=0.00..43020.87 rows=1456007 width=14) (actual time=0.010..360.023 rows=1510902 loops=1)
Output: i."paidInstallment", i.frequency, i.id
Filter: (i."deletedAt" IS NULL)
Rows Removed by Filter: 24993
Buffers: shared hit=28209
-> Hash (cost=3845.53..3845.53 rows=68875 width=12) (actual time=41.500..41.500 rows=69253 loops=1)
Output: l.plafond, l.tenor, l.id
Buckets: 131072 Batches: 2 Memory Usage: 2655kB
Buffers: shared hit=3132, temp written=151
-> Seq Scan on public.loan l (cost=0.00..3845.53 rows=68875 width=12) (actual time=0.005..25.918 rows=69253 loops=1)
Output: l.plafond, l.tenor, l.id
Filter: (l."deletedAt" IS NULL)
Rows Removed by Filter: 2611
Buffers: shared hit=3132
-> Materialize (cost=31566.41..109504.70 rows=461 width=4) (actual time=0.002..0.130 rows=2117 loops=1496484)
Output: ratd."accountId"
Buffers: shared hit=31483, temp read=208 written=206
-> Hash Join (cost=31566.41..109502.39 rows=461 width=4) (actual time=2253.937..2295.318 rows=2117 loops=1)
Output: ratd."accountId"
Hash Cond: ((atd.id)::double precision = ratd."accountTransactionDebitId")
Buffers: shared hit=31483, temp read=208 written=206
-> Seq Scan on public.account_transaction_debit atd (cost=0.00..77463.04 rows=7467 width=4) (actual time=2048.273..2078.574 rows=20319 loops=1)
Output: atd.id
Filter: ((atd."deletedAt" IS NULL) AND (atd.type = 'INSTALLMENT'::text) AND ((atd."createdAt")::date <= ('now'::cstring)::date) AND ((atd."createdAt")::date >= date_trunc('week'::text, (('now'::cstring)::date)::timestamp with time zone)))
Rows Removed by Filter: 1496536
Buffers: shared hit=20688
-> Hash (cost=30009.74..30009.74 rows=94854 width=8) (actual time=205.009..205.009 rows=102568 loops=1)
Output: ratd."accountTransactionDebitId", ratd."accountId"
Buckets: 131072 Batches: 2 Memory Usage: 3021kB
Buffers: shared hit=10795, temp written=175
-> Seq Scan on public.r_account_transaction_debit ratd (cost=0.00..30009.74 rows=94854 width=8) (actual time=17.923..180.127 rows=102568 loops=1)
Output: ratd."accountTransactionDebitId", ratd."accountId"
Filter: ((ratd."deletedAt" IS NULL) AND (ratd."accountId" = 4735))
Rows Removed by Filter: 1414286
Buffers: shared hit=10795
Planning time: 1.181 ms
Execution time: 3020772.395 ms
我已经搜索了解决方案，但没有解决我的问题，我有什么选择吗？
答案 0 :(得分：2)
通常，仅当where子句中的表达式与完全索引表达式匹配时才使用索引。加上该指数的前导列是首选。
你不要在my_to_char("createdAt")子句中使用where，而是使用表达式`“createdAt”:: date。
你需要在"createdAt"::date上定义一个索引 - 这是一个更好的选择，因为它会使索引更小。 date以4个字节存储，字符表示占用10个字节。
在查询中仅引用"createdAt"::date时，该表达式也应该是索引的前导表达式。即使您更改了使用"createdAt"::date的唯一索引，也很可能不会使用它。
以下索引应该有所帮助：
CREATE INDEX ON account_transaction_debit ( ("createdAt"::date) );
由于您在deletedAt和type上加入条件，部分索引可能会更好：
CREATE INDEX ON account_transaction_debit ( ("createdAt"::date), type )
where "deletedAt" is null;
修改
您忘了提到您使用的timestamp with time zone列使事情变得复杂（这是一个很好的例子，为什么包含create table语句总是一个好主意）。
您仍然可以使用日期值，但您需要更改功能，查询和索引：
CREATE OR REPLACE FUNCTION get_date(some_time timestamptz)
RETURNS date
AS
$BODY$
select some_time::date
$BODY$
LANGUAGE sql
IMMUTABLE;
然后你可以创建这个索引：
CREATE INDEX ON account_transaction_debit ( (get_date("createdAt")), type )
where "deletedAt" is null;
然后在查询中使用以下条件：
where get_date(atd."createdAt") between date_trunc('week',current_date) and current_date;