PostgreSQL是否存在简单的忽略大小写比较？
我想替换：
SELECT id, user_name
FROM users
WHERE lower(email) IN (lower('adamB@a.com'), lower('eveA@b.com'));
有类似的东西：
SELECT id, user_name
FROM users
WHERE email IGNORE_CASE_IN ('adamB@a.com', 'eveA@b.com');
like和ilike运算符处理单个值（例如like 'adamB@a.com'），但不处理集合。
答案 0 :(得分：45)
select *
where email ilike 'me@example.com'
ilike与like类似，但不区分大小写。对于转义字符使用replace()
where email ilike replace(replace(replace($1, '~', '~~'), '%', '~%'), '_', '~_') escape '~'
或者您可以创建一个函数来转义文本;用于文本数组
where email ilike any(array['adamB@a.com', 'eveA@b.com'])
答案 1 :(得分：18)
首先，不要做什么，不要使用ilike ......
create table y
(
id serial not null,
email text not null unique
);
insert into y(email)
values('iSteve.jobs@apple.com') ,('linus.Torvalds@linUX.com');
insert into y(email)
select n from generate_series(1,1000) as i(n);
create index ix_y on y(email);
explain select * from y
where email ilike
ANY(ARRAY['ISteve.Jobs@Apple.com','Linus.Torvalds@Linux.com']);
执行计划：
memdb=# explain select * from y where email ilike ANY(ARRAY['ISteve.Jobs@Apple.com','Linus.Torvalds@Linux.com']);
QUERY PLAN
----------------------------------------------------------------------------------------
Seq Scan on y (cost=0.00..17.52 rows=1 width=7)
Filter: (email ~~* ANY ('{ISteve.Jobs@Apple.com,Linus.Torvalds@Linux.com}'::text[]))
(2 rows)
要么你创建一个索引的低级表达式......
create function lower(t text[]) returns text[]
as
$$
select lower($1::text)::text[]
$$ language sql;
create unique index ix_y_2 on y(lower(email));
explain select * from y
where lower(email) =
ANY(lower(ARRAY['ISteve.Jobs@Apple.com','Linus.Torvalds@Linux.com']));
...正确使用索引：
memdb=# explain select * from y where lower(email) = ANY(lower(ARRAY['ISteve.Jobs@Apple.com','Linus.Torvalds@Linux.com']));
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on y (cost=22.60..27.98 rows=10 width=7)
Recheck Cond: (lower(email) = ANY ((lower(('{ISteve.Jobs@Apple.com,Linus.Torvalds@Linux.com}'::text[])::text))::text[]))
-> Bitmap Index Scan on ix_y_2 (cost=0.00..22.60 rows=10 width=0)
Index Cond: (lower(email) = ANY ((lower(('{ISteve.Jobs@Apple.com,Linus.Torvalds@Linux.com}'::text[])::text))::text[]))
(4 rows)
或者您使用citext数据类型...
create table x
(
id serial not null,
email citext not null unique
);
insert into x(email)
values('iSteve.jobs@apple.com'),('linus.Torvalds@linUX.com');
insert into x(email)
select n from generate_series(1,1000) as i(n);
create index ix_x on x(email);
explain select * from x
where email =
ANY(ARRAY['ISteve.Jobs@Apple.com','Linus.Torvalds@Linux.com']::citext[]);
...即使您没有在表达式上创建索引（例如，在yyy（lower（field）上创建索引zzz））也正确使用索引：
memdb=# explain select * from x where email = ANY(ARRAY['ISteve.Jobs@Apple.com','Linus.Torvalds@Linux.com']::citext[]);
QUERY PLAN
--------------------------------------------------------------------------------------------------
Bitmap Heap Scan on x (cost=8.52..12.75 rows=2 width=7)
Recheck Cond: (email = ANY ('{ISteve.Jobs@Apple.com,Linus.Torvalds@Linux.com}'::citext[]))
-> Bitmap Index Scan on ix_x (cost=0.00..8.52 rows=2 width=0)
Index Cond: (email = ANY ('{ISteve.Jobs@Apple.com,Linus.Torvalds@Linux.com}'::citext[]))
(4 rows)
答案 2 :(得分：11)
使用不区分大小写的文本数据类型。使用citext：
create table emails
(
user_id int references users(user_id)
email citext
);
insert into emails(user_id, email) values(1, 'linus.Torvalds@linUX.com');
insert into emails(user_id, email) values(2, 'iSteve.jobs@apple.com');
select * from emails where email in ('linus.torvalds@Linux.com','isteve.jobs@Apple.com');
如果您在contrib目录中找不到citext.sql，请将其复制并粘贴到您的pgAdmin：
/* $PostgreSQL: pgsql/contrib/citext/citext.sql.in,v 1.3 2008/09/05 18:25:16 tgl Exp $ */
-- Adjust this setting to control where the objects get created.
SET search_path = public;
--
-- PostgreSQL code for CITEXT.
--
-- Most I/O functions, and a few others, piggyback on the "text" type
-- functions via the implicit cast to text.
--
--
-- Shell type to keep things a bit quieter.
--
CREATE TYPE citext;
--
-- Input and output functions.
--
CREATE OR REPLACE FUNCTION citextin(cstring)
RETURNS citext
AS 'textin'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citextout(citext)
RETURNS cstring
AS 'textout'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citextrecv(internal)
RETURNS citext
AS 'textrecv'
LANGUAGE internal STABLE STRICT;
CREATE OR REPLACE FUNCTION citextsend(citext)
RETURNS bytea
AS 'textsend'
LANGUAGE internal STABLE STRICT;
--
-- The type itself.
--
CREATE TYPE citext (
INPUT = citextin,
OUTPUT = citextout,
RECEIVE = citextrecv,
SEND = citextsend,
INTERNALLENGTH = VARIABLE,
STORAGE = extended,
-- make it a non-preferred member of string type category
CATEGORY = 'S',
PREFERRED = false
);
--
-- Type casting functions for those situations where the I/O casts don't
-- automatically kick in.
--
CREATE OR REPLACE FUNCTION citext(bpchar)
RETURNS citext
AS 'rtrim1'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citext(boolean)
RETURNS citext
AS 'booltext'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citext(inet)
RETURNS citext
AS 'network_show'
LANGUAGE internal IMMUTABLE STRICT;
--
-- Implicit and assignment type casts.
--
CREATE CAST (citext AS text) WITHOUT FUNCTION AS IMPLICIT;
CREATE CAST (citext AS varchar) WITHOUT FUNCTION AS IMPLICIT;
CREATE CAST (citext AS bpchar) WITHOUT FUNCTION AS ASSIGNMENT;
CREATE CAST (text AS citext) WITHOUT FUNCTION AS ASSIGNMENT;
CREATE CAST (varchar AS citext) WITHOUT FUNCTION AS ASSIGNMENT;
CREATE CAST (bpchar AS citext) WITH FUNCTION citext(bpchar) AS ASSIGNMENT;
CREATE CAST (boolean AS citext) WITH FUNCTION citext(boolean) AS ASSIGNMENT;
CREATE CAST (inet AS citext) WITH FUNCTION citext(inet) AS ASSIGNMENT;
--
-- Operator Functions.
--
CREATE OR REPLACE FUNCTION citext_eq( citext, citext )
RETURNS bool
AS '$libdir/citext'
LANGUAGE C IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citext_ne( citext, citext )
RETURNS bool
AS '$libdir/citext'
LANGUAGE C IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citext_lt( citext, citext )
RETURNS bool
AS '$libdir/citext'
LANGUAGE C IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citext_le( citext, citext )
RETURNS bool
AS '$libdir/citext'
LANGUAGE C IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citext_gt( citext, citext )
RETURNS bool
AS '$libdir/citext'
LANGUAGE C IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citext_ge( citext, citext )
RETURNS bool
AS '$libdir/citext'
LANGUAGE C IMMUTABLE STRICT;
--
-- Operators.
--
CREATE OPERATOR = (
LEFTARG = CITEXT,
RIGHTARG = CITEXT,
COMMUTATOR = =,
NEGATOR = <>,
PROCEDURE = citext_eq,
RESTRICT = eqsel,
JOIN = eqjoinsel,
HASHES,
MERGES
);
CREATE OPERATOR <> (
LEFTARG = CITEXT,
RIGHTARG = CITEXT,
NEGATOR = =,
COMMUTATOR = <>,
PROCEDURE = citext_ne,
RESTRICT = neqsel,
JOIN = neqjoinsel
);
CREATE OPERATOR < (
LEFTARG = CITEXT,
RIGHTARG = CITEXT,
NEGATOR = >=,
COMMUTATOR = >,
PROCEDURE = citext_lt,
RESTRICT = scalarltsel,
JOIN = scalarltjoinsel
);
CREATE OPERATOR <= (
LEFTARG = CITEXT,
RIGHTARG = CITEXT,
NEGATOR = >,
COMMUTATOR = >=,
PROCEDURE = citext_le,
RESTRICT = scalarltsel,
JOIN = scalarltjoinsel
);
CREATE OPERATOR >= (
LEFTARG = CITEXT,
RIGHTARG = CITEXT,
NEGATOR = <,
COMMUTATOR = <=,
PROCEDURE = citext_ge,
RESTRICT = scalargtsel,
JOIN = scalargtjoinsel
);
CREATE OPERATOR > (
LEFTARG = CITEXT,
RIGHTARG = CITEXT,
NEGATOR = <=,
COMMUTATOR = <,
PROCEDURE = citext_gt,
RESTRICT = scalargtsel,
JOIN = scalargtjoinsel
);
--
-- Support functions for indexing.
--
CREATE OR REPLACE FUNCTION citext_cmp(citext, citext)
RETURNS int4
AS '$libdir/citext'
LANGUAGE C STRICT IMMUTABLE;
CREATE OR REPLACE FUNCTION citext_hash(citext)
RETURNS int4
AS '$libdir/citext'
LANGUAGE C STRICT IMMUTABLE;
--
-- The btree indexing operator class.
--
CREATE OPERATOR CLASS citext_ops
DEFAULT FOR TYPE CITEXT USING btree AS
OPERATOR 1 < (citext, citext),
OPERATOR 2 <= (citext, citext),
OPERATOR 3 = (citext, citext),
OPERATOR 4 >= (citext, citext),
OPERATOR 5 > (citext, citext),
FUNCTION 1 citext_cmp(citext, citext);
--
-- The hash indexing operator class.
--
CREATE OPERATOR CLASS citext_ops
DEFAULT FOR TYPE citext USING hash AS
OPERATOR 1 = (citext, citext),
FUNCTION 1 citext_hash(citext);
--
-- Aggregates.
--
CREATE OR REPLACE FUNCTION citext_smaller(citext, citext)
RETURNS citext
AS '$libdir/citext'
LANGUAGE 'C' IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION citext_larger(citext, citext)
RETURNS citext
AS '$libdir/citext'
LANGUAGE 'C' IMMUTABLE STRICT;
CREATE AGGREGATE min(citext) (
SFUNC = citext_smaller,
STYPE = citext,
SORTOP = <
);
CREATE AGGREGATE max(citext) (
SFUNC = citext_larger,
STYPE = citext,
SORTOP = >
);
--
-- CITEXT pattern matching.
--
CREATE OR REPLACE FUNCTION texticlike(citext, citext)
RETURNS bool AS 'texticlike'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION texticnlike(citext, citext)
RETURNS bool AS 'texticnlike'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION texticregexeq(citext, citext)
RETURNS bool AS 'texticregexeq'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION texticregexne(citext, citext)
RETURNS bool AS 'texticregexne'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OPERATOR ~ (
PROCEDURE = texticregexeq,
LEFTARG = citext,
RIGHTARG = citext,
NEGATOR = !~,
RESTRICT = icregexeqsel,
JOIN = icregexeqjoinsel
);
CREATE OPERATOR ~* (
PROCEDURE = texticregexeq,
LEFTARG = citext,
RIGHTARG = citext,
NEGATOR = !~*,
RESTRICT = icregexeqsel,
JOIN = icregexeqjoinsel
);
CREATE OPERATOR !~ (
PROCEDURE = texticregexne,
LEFTARG = citext,
RIGHTARG = citext,
NEGATOR = ~,
RESTRICT = icregexnesel,
JOIN = icregexnejoinsel
);
CREATE OPERATOR !~* (
PROCEDURE = texticregexne,
LEFTARG = citext,
RIGHTARG = citext,
NEGATOR = ~*,
RESTRICT = icregexnesel,
JOIN = icregexnejoinsel
);
CREATE OPERATOR ~~ (
PROCEDURE = texticlike,
LEFTARG = citext,
RIGHTARG = citext,
NEGATOR = !~~,
RESTRICT = iclikesel,
JOIN = iclikejoinsel
);
CREATE OPERATOR ~~* (
PROCEDURE = texticlike,
LEFTARG = citext,
RIGHTARG = citext,
NEGATOR = !~~*,
RESTRICT = iclikesel,
JOIN = iclikejoinsel
);
CREATE OPERATOR !~~ (
PROCEDURE = texticnlike,
LEFTARG = citext,
RIGHTARG = citext,
NEGATOR = ~~,
RESTRICT = icnlikesel,
JOIN = icnlikejoinsel
);
CREATE OPERATOR !~~* (
PROCEDURE = texticnlike,
LEFTARG = citext,
RIGHTARG = citext,
NEGATOR = ~~*,
RESTRICT = icnlikesel,
JOIN = icnlikejoinsel
);
--
-- Matching citext to text.
--
CREATE OR REPLACE FUNCTION texticlike(citext, text)
RETURNS bool AS 'texticlike'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION texticnlike(citext, text)
RETURNS bool AS 'texticnlike'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION texticregexeq(citext, text)
RETURNS bool AS 'texticregexeq'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION texticregexne(citext, text)
RETURNS bool AS 'texticregexne'
LANGUAGE internal IMMUTABLE STRICT;
CREATE OPERATOR ~ (
PROCEDURE = texticregexeq,
LEFTARG = citext,
RIGHTARG = text,
NEGATOR = !~,
RESTRICT = icregexeqsel,
JOIN = icregexeqjoinsel
);
CREATE OPERATOR ~* (
PROCEDURE = texticregexeq,
LEFTARG = citext,
RIGHTARG = text,
NEGATOR = !~*,
RESTRICT = icregexeqsel,
JOIN = icregexeqjoinsel
);
CREATE OPERATOR !~ (
PROCEDURE = texticregexne,
LEFTARG = citext,
RIGHTARG = text,
NEGATOR = ~,
RESTRICT = icregexnesel,
JOIN = icregexnejoinsel
);
CREATE OPERATOR !~* (
PROCEDURE = texticregexne,
LEFTARG = citext,
RIGHTARG = text,
NEGATOR = ~*,
RESTRICT = icregexnesel,
JOIN = icregexnejoinsel
);
CREATE OPERATOR ~~ (
PROCEDURE = texticlike,
LEFTARG = citext,
RIGHTARG = text,
NEGATOR = !~~,
RESTRICT = iclikesel,
JOIN = iclikejoinsel
);
CREATE OPERATOR ~~* (
PROCEDURE = texticlike,
LEFTARG = citext,
RIGHTARG = text,
NEGATOR = !~~*,
RESTRICT = iclikesel,
JOIN = iclikejoinsel
);
CREATE OPERATOR !~~ (
PROCEDURE = texticnlike,
LEFTARG = citext,
RIGHTARG = text,
NEGATOR = ~~,
RESTRICT = icnlikesel,
JOIN = icnlikejoinsel
);
CREATE OPERATOR !~~* (
PROCEDURE = texticnlike,
LEFTARG = citext,
RIGHTARG = text,
NEGATOR = ~~*,
RESTRICT = icnlikesel,
JOIN = icnlikejoinsel
);
--
-- Matching citext in string comparison functions.
-- XXX TODO Ideally these would be implemented in C.
--
CREATE OR REPLACE FUNCTION regexp_matches( citext, citext ) RETURNS TEXT[] AS $$
SELECT pg_catalog.regexp_matches( $1::pg_catalog.text, $2::pg_catalog.text, 'i' );
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION regexp_matches( citext, citext, text ) RETURNS TEXT[] AS $$
SELECT pg_catalog.regexp_matches( $1::pg_catalog.text, $2::pg_catalog.text, CASE WHEN pg_catalog.strpos($3, 'c') = 0 THEN $3 || 'i' ELSE $3 END );
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION regexp_replace( citext, citext, text ) returns TEXT AS $$
SELECT pg_catalog.regexp_replace( $1::pg_catalog.text, $2::pg_catalog.text, $3, 'i');
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION regexp_replace( citext, citext, text, text ) returns TEXT AS $$
SELECT pg_catalog.regexp_replace( $1::pg_catalog.text, $2::pg_catalog.text, $3, CASE WHEN pg_catalog.strpos($4, 'c') = 0 THEN $4 || 'i' ELSE $4 END);
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION regexp_split_to_array( citext, citext ) RETURNS TEXT[] AS $$
SELECT pg_catalog.regexp_split_to_array( $1::pg_catalog.text, $2::pg_catalog.text, 'i' );
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION regexp_split_to_array( citext, citext, text ) RETURNS TEXT[] AS $$
SELECT pg_catalog.regexp_split_to_array( $1::pg_catalog.text, $2::pg_catalog.text, CASE WHEN pg_catalog.strpos($3, 'c') = 0 THEN $3 || 'i' ELSE $3 END );
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION regexp_split_to_table( citext, citext ) RETURNS SETOF TEXT AS $$
SELECT pg_catalog.regexp_split_to_table( $1::pg_catalog.text, $2::pg_catalog.text, 'i' );
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION regexp_split_to_table( citext, citext, text ) RETURNS SETOF TEXT AS $$
SELECT pg_catalog.regexp_split_to_table( $1::pg_catalog.text, $2::pg_catalog.text, CASE WHEN pg_catalog.strpos($3, 'c') = 0 THEN $3 || 'i' ELSE $3 END );
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION strpos( citext, citext ) RETURNS INT AS $$
SELECT pg_catalog.strpos( pg_catalog.lower( $1::pg_catalog.text ), pg_catalog.lower( $2::pg_catalog.text ) );
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION replace( citext, citext, citext ) RETURNS TEXT AS $$
SELECT pg_catalog.regexp_replace( $1::pg_catalog.text, pg_catalog.regexp_replace($2::pg_catalog.text, '([^a-zA-Z_0-9])', E'\\\\\\1', 'g'), $3::pg_catalog.text, 'gi' );
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION split_part( citext, citext, int ) RETURNS TEXT AS $$
SELECT (pg_catalog.regexp_split_to_array( $1::pg_catalog.text, pg_catalog.regexp_replace($2::pg_catalog.text, '([^a-zA-Z_0-9])', E'\\\\\\1', 'g'), 'i'))[$3];
$$ LANGUAGE SQL IMMUTABLE STRICT;
CREATE OR REPLACE FUNCTION translate( citext, citext, text ) RETURNS TEXT AS $$
SELECT pg_catalog.translate( pg_catalog.translate( $1::pg_catalog.text, pg_catalog.lower($2::pg_catalog.text), $3), pg_catalog.upper($2::pg_catalog.text), $3);
$$ LANGUAGE SQL IMMUTABLE STRICT;
答案 3 :(得分：10)
自从这个问题得到解答以及建议不要使用ILIKE＆＃34;不再是真的（至少以这种一般方式）。
事实上，根据数据分布，带有trigram index的ILIKE甚至可能比app.controller('myCtrl',function(httpCall) {
httpCall.callAPI()
.then(function(res) {
if (res.data.length>0) {
callback(data);
}
}, function(err) {
if (callback) {
callback(null, data);
}
});
});
更快。
对于一个独特的索引，确实存在很大差异，使用迈克尔的测试设置时可以看到：
citext使用create table y
(
id serial not null,
email text not null unique
);
insert into y(email)
select 'some.name'||n||'@foobar.com'
from generate_series(1,100000) as i(n);
-- create a trigram index to support ILIKE
create index ix_y on y using gin (email gin_trgm_ops);
create table x
(
id serial not null,
email citext not null unique
);
-- no need to create an index
-- the UNIQUE constraint will create a regular B-Tree index
insert into x(email)
select email
from y;
的执行计划：
ILIKEexplain (analyze)
select *
from y
where email ilike ANY (ARRAY['Some.Name420@foobar.com','Some.Name42@foobar.com']);
使用Bitmap Heap Scan on y (cost=126.07..154.50 rows=20 width=29) (actual time=60.696..60.818 rows=2 loops=1)
Recheck Cond: (email ~~* ANY ('{Some.Name420@foobar.com,Some.Name42@foobar.com}'::text[]))
Rows Removed by Index Recheck: 13
Heap Blocks: exact=11
-> Bitmap Index Scan on ix_y (cost=0.00..126.07 rows=20 width=0) (actual time=60.661..60.661 rows=15 loops=1)
Index Cond: (email ~~* ANY ('{Some.Name420@foobar.com,Some.Name42@foobar.com}'::text[]))
Planning time: 0.952 ms
Execution time: 61.004 ms
：
citextexplain (analyze)
select *
from x
where email = ANY (ARRAY['Some.Name420@foobar.com','Some.Name42@foobar.com']);
请注意，Index Scan using x_email_key on x (cost=0.42..5.85 rows=2 width=29) (actual time=0.111..0.203 rows=2 loops=1)
Index Cond: (email = ANY ('{Some.Name420@foobar.com,Some.Name42@foobar.com}'::citext[]))
Planning time: 0.115 ms
Execution time: 0.254 ms
查询实际上与citext的ILIKE查询不同，因为ILIKE会遵循通配符。
然而，对于非唯一索引，事情看起来不同。以下设置基于recent question提出相同的要求：
=因此，每个表中有一百万行，create table data
(
group_id serial primary key,
name text
);
create table data_ci
(
group_id serial primary key,
name citext
);
insert into data(name)
select 'data'||i.n
from generate_series(1,1000) as i(n), generate_series(1,1000) as i2(n);
insert into data_ci(group_id, name)
select group_id, name
from data;
create index ix_data_gin on data using gin (name public.gin_trgm_ops);
create index ix_data_ci on data_ci (name);
列有1000个不同的值，对于每个不同的值，我们有1000个重复的值。因此，查找3个不同值的查询将返回3000行。
在这种情况下，三元组索引比BTree索引快得多：
nameexplain (analyze)
select *
from data
where name ilike any (array['Data1', 'data2', 'DATA3']);
citext列上的btree索引现在使用Seq Scan
Bitmap Heap Scan on data (cost=88.25..1777.61 rows=1535 width=11) (actual time=2.906..11.064 rows=3000 loops=1)
Recheck Cond: (name ~~* ANY ('{Data1,data2,DATA3}'::text[]))
Heap Blocks: exact=17
-> Bitmap Index Scan on ix_data_gin (cost=0.00..87.87 rows=1535 width=0) (actual time=2.869..2.869 rows=3000 loops=1)
Index Cond: (name ~~* ANY ('{Data1,data2,DATA3}'::text[]))
Planning time: 2.174 ms
Execution time: 11.282 ms
explain analyze
select *
from data_ci
where name = any (array['Data1', 'data2', 'DATA3']);
GIN索引的大小实际上小于Seq Scan on data_ci (cost=0.00..10156.00 rows=2904 width=11) (actual time=0.449..304.301 rows=1000 loops=1)
Filter: ((name)::text = ANY ('{Data1,data2,DATA3}'::text[]))
Rows Removed by Filter: 999000
Planning time: 0.152 ms
Execution time: 304.360 ms
列的大小：
citextselect pg_size_pretty(pg_total_relation_size('ix_data_gin')) as gin_index_size,
pg_size_pretty(pg_total_relation_size('ix_data_ci')) as citex_index_size
以上是在Windows笔记本电脑上使用Postgres 9.6.1完成的，gin_index_size | citex_index_size
---------------+-----------------
11 MB | 21 MB
设置为1.5
答案 4 :(得分：3)
您还可以在较低（电子邮件）上创建索引。
答案 5 :(得分：-3)
Use ‘Collate SQL_Latin1_General_CP1_CS_AS’ for it.
declare @a nvarchar(5)='a'
declare @b nvarchar(5)='A'
if(@a=@b Collate SQL_Latin1_General_CP1_CS_AS)
begin
print 'Match'
end
else
begin
print 'Not Matched'
end