如何在sqlite中使用where子句在表上创建部分索引？

我有一张200万行的桌子。我已经在（唯一列的表达式）上创建了索引。该表达式将列的值映射到较小的数字空间，这意味着该表达式的结果不是唯一的。现在我想在（

该表达式的DISTINCT

）上创建索引。我希望再次在表达式上创建索引的原因是DISTINCT和GROUP BY查询运行缓慢（~900ms）

我需要的是这个

CREATE INDEX idx ON mytable(DISTINCT myColumn|9223372036854775806);       //invalid

我已经知道的是

CREATE INDEX idx ON mytable(myColumn|9223372036854775806);

---

我的最终目标是使下面的查询更快（DISTINCT只能用作SELECT的一部分，即删除重复的行

DISTINCT的补码是ALL，这是默认值，因此您很少看到ALL

索引必须包含它所覆盖的所有行的一个条目，因此DISTINCT将违反索引的目的，因为所覆盖的某些行将被忽略

在mytable（myColumn | 9223372036854775806）

上创建索引idx所做的是将索引拆分为两个主要组/分支，因为

9223372036854775806

会导致

9223372036854775806

或

9223372036854775807

，因为这样的不同会导致两行（通常）例如使用

SELECT DISTINCT mycolumn,myColumn|9223372036854775806 AS x FROM mytable;

结果（根据下面的测试代码，从填充有100万行随机值的表中）：-

• i、 e 2行，与行数无关
  • （除非数字非常低，并且当只有一行时，

    myColumn | 9223372036854775806

    的所有值都是相同的结果）

部分索引 部分索引是使用WHERE子句减少索引行的索引，如果查询满足两个规则之一，则选择该索引

从理论上讲，您可以使用（只需固定两行）：-

• 但是，如果部分索引中的子句

因此，您似乎希望确定创建索引的方法，例如，您可以使用以下方法将索引拆分为10个部分索引：-

CREATE INDEX idx10 ON mytable(mycolumn) WHERE mycolumn < 9223372036854775806 / 10;
CREATE INDEX idx20 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 10 AND mycolumn < 9223372036854775806 / 20;
CREATE INDEX idx30 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 20 AND mycolumn < 9223372036854775806 / 30;
...... and so on
CREATE INDEX idx100 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 90;

在mytable（mycolumn）上创建索引idx10，其中mycolumn<9223372036854775806/10；
在mytable（mycolumn）上创建索引idx20，其中mycolumn>=9223372036854775806/10和mycolumn<9223372036854775806/20；
在mytable（mycolumn）上创建索引idx30，其中mycolumn>=9223372036854775806/20和mycolumn<9223372036854775806/30；
等等
在mytable（mycolumn）上创建索引idx100，其中mycolumn>=9223372036854775806/90；

在这种情况下：-

EXPLAIN QUERY PLAN
SELECT mycolumn FROM mytable WHERE mycolumn < 9223372036854775806 / 10 LIMIT 100;

解释查询计划
从mytable中选择mycolumn，其中mycolumn<9223372036854775806/10 LIMIT 100；

结果：-

• i、 eidx10已由查询计划器选择，因为它已确定SELECT的WHERE子句适合使用索引ix10

• 注意以上只是部分索引的一个示例，它可能不适合您的结果。

测试代码 以上部分内容是通过使用以下代码进行测试生成的，您可能会发现这些代码很有用：-

DROP TABLE IF EXISTS mytable;
DROP INDEX IF EXISTS idx1;
DROP INDEX IF EXISTS idx2;
DROP INDEX IF EXISTS idx10;
DROP INDEX IF EXISTS idx20;
DROP INDEX IF EXISTS idx30;
DROP INDEX IF EXISTS idx40;
DROP INDEX IF EXISTS idx50;
DROP INDEX IF EXISTS idx60;
DROP INDEX IF EXISTS idx70;
DROP INDEX IF EXISTS idx80;
DROP INDEX IF EXISTS idx90;
DROP INDEX IF EXISTS idx100;
CREATE TABLE IF NOT EXISTS mytable (id INTEGER PRIMARY KEY, mycolumn INTEGER DEFAULT (CAST(abs(random()) AS INTEGER)));
CREATE INDEX idx1 ON mytable(myColumn|9223372036854775806);
-- CREATE INDEX idx2 ON mytable(DISTINCT myColumn|9223372036854775806); CANNOT BE USED AS DISTINCT is syntax error.
-- CREATE INDEX idx3 ON mytable(myColumn) WHERE myColumn =  (SELECT DISTINCT myColumn|9223372036854775806 FROM mytable);
CREATE INDEX idx10 ON mytable(mycolumn) WHERE mycolumn < 9223372036854775806 / 10;
CREATE INDEX idx20 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 10 AND mycolumn < 9223372036854775806 / 20;
CREATE INDEX idx30 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 20 AND mycolumn < 9223372036854775806 / 30;
CREATE INDEX idx40 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 30 AND mycolumn < 9223372036854775806 / 40;
CREATE INDEX idx50 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 40 AND mycolumn < 9223372036854775806 / 50;
CREATE INDEX idx60 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 50 AND mycolumn < 9223372036854775806 / 60;
CREATE INDEX idx70 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 60 AND mycolumn < 9223372036854775806 / 70;
CREATE INDEX idx80 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 70 AND mycolumn < 9223372036854775806 / 80;
CREATE INDEX idx90 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 80 AND mycolumn < 9223372036854775806 / 90;
CREATE INDEX idx100 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 90;
/* Load some data */
WITH RECURSIVE cte(x,y) AS (
    SELECT 1,CAST(abs(random()) AS INTEGER)
    UNION ALL SELECT x+1,CAST(abs(random()) AS INTEGER) FROM cte LIMIT 1000000
)
INSERT INTO mytable (mycolumn) SELECT y FROM cte;

/* Show some sample data */
SELECT mycolumn,myColumn|9223372036854775806 AS x FROM mytable LIMIT 100;

/* LOOK AT WHAT THE QUERY PLANNER COMES UP WITH */
EXPLAIN QUERY PLAN
SELECT DISTINCT mycolumn,myColumn|9223372036854775806 AS x FROM mytable;
EXPLAIN QUERY PLAN
SELECT /*(SELECT count() FROM mytable) AS rows,*/*, mycolumn|9223372036854775806 AS x FROM mytable GROUP BY myColumn|9223372036854775806;


SELECT DISTINCT mycolumn,myColumn|9223372036854775806 AS x FROM mytable LIMIT 100;
SELECT /*(SELECT count() FROM mytable) AS rows,*/*, mycolumn|9223372036854775806 AS x FROM mytable GROUP BY myColumn|9223372036854775806;

EXPLAIN QUERY PLAN
SELECT mycolumn FROM mytable WHERE mycolumn < 9223372036854775806 / 10 LIMIT 100;

SELECT mycolumn FROM mytable WHERE mycolumn < 9223372036854775806 / 10 LIMIT 100;

/* CLEAN UP */
DROP TABLE IF EXISTS mytable;
DROP INDEX IF EXISTS idx1;
DROP INDEX IF EXISTS idx2;
DROP INDEX IF EXISTS idx10;
DROP INDEX IF EXISTS idx20;
DROP INDEX IF EXISTS idx30;
DROP INDEX IF EXISTS idx40;
DROP INDEX IF EXISTS idx50;
DROP INDEX IF EXISTS idx60;
DROP INDEX IF EXISTS idx70;
DROP INDEX IF EXISTS idx80;
DROP INDEX IF EXISTS idx90;
DROP INDEX IF EXISTS idx100;

如果mytable存在，则删除表；
如果存在idx1，则删除索引；
如果存在idx2，则删除索引；
如果存在，则删除索引idx10；
如果存在idx20，则删除索引；
如果存在idx30，则删除索引；
如果存在idx40，则删除索引；
如果存在idx50，则删除索引；
如果存在idx60，则删除索引；
如果存在idx70，则删除索引；
如果存在idx80，则删除索引；
如果存在idx90，则删除索引；
如果存在，则删除索引idx100；
如果不存在，则创建表mytable（id INTEGER主键，mycolumn INTEGER默认值（CAST（abs（random（））AS INTEGER））；
在mytable（myColumn | 9223372036854775806）上创建索引idx1；
--在mytable上创建索引idx2（DISTINCT myColumn | 9223372036854775806）；不能使用，因为DISTINCT is语法错误。
--在mytable（myColumn）上创建索引idx3，其中myColumn=（从mytable中选择不同的myColumn | 9223372036854775806）；
在mytable（mycolumn）上创建索引idx10，其中mycolumn<9223372036854775806/10；
在mytable（mycolumn）上创建索引idx20，其中mycolumn>=9223372036854775806/10和mycolumn<9223372036854775806/20；
在mytable（mycolumn）上创建索引idx30，其中mycolumn>=9223372036854775806/20和mycolumn<9223372036854775806/30；
在mytable（mycolumn）上创建索引idx40，其中mycolumn>=9223372036854775806/30和mycolumn<9223372036854775806/40；
在mytable（mycolumn）上创建索引idx50，其中mycolumn>=9223372036854775806/40和mycolumn<9223372036854775806/50；
在mytable（mycolumn）上创建索引idx60，其中mycolumn>=9223372036854775806/50和mycolumn<9223372036854775806/60；
在mytable（mycolumn）上创建索引idx70，其中mycolumn>=9223372036854775806/60和mycolumn<9223372036854775806/70；
在mytable（mycolumn）上创建索引idx80，其中mycolumn>=9223372036854775806/70和mycolumn<9223372036854775806/80；
在mytable（mycolumn）上创建索引idx90，其中mycolumn>=9223372036854775806/80和mycolumn<9223372036854775806/90；
在mytable（mycolumn）上创建索引idx100，其中mycolumn>=9223372036854775806/90；
/*加载一些数据*/
递归cte（x，y）为(
选择1，强制转换（abs（random（））为整数）
UNION ALL选择x+1，从cte LIMIT 1000000中强制转换（abs（random（））为整数）
)
插入mytable（mycolumn）中，从cte中选择y；
/*显示一些示例数据*/
从mytable LIMIT 100中选择mycolumn，mycolumn | 9223372036854775806作为x；
/*看看查询计划器得出的结果*/
解释查询计划
从mytable中选择不同的mycolumn，mycolumn | 9223372036854775806作为x；
解释查询计划
按mycolumn | 9223372036854775806从mytable组中选择/*（从mytable中选择count（）作为行，*/*，mycolumn | 9223372036854775806作为x；
从mytable LIMIT 100中选择不同的mycolumn，mycolumn | 9223372036854775806作为x；
选择/*（从mytable中选择count（））作为行，*/*，mycolumn | 922
EXPLAIN QUERY PLAN
SELECT mycolumn FROM mytable WHERE mycolumn < 9223372036854775806 / 10 LIMIT 100;

DROP TABLE IF EXISTS mytable;
DROP INDEX IF EXISTS idx1;
DROP INDEX IF EXISTS idx2;
DROP INDEX IF EXISTS idx10;
DROP INDEX IF EXISTS idx20;
DROP INDEX IF EXISTS idx30;
DROP INDEX IF EXISTS idx40;
DROP INDEX IF EXISTS idx50;
DROP INDEX IF EXISTS idx60;
DROP INDEX IF EXISTS idx70;
DROP INDEX IF EXISTS idx80;
DROP INDEX IF EXISTS idx90;
DROP INDEX IF EXISTS idx100;
CREATE TABLE IF NOT EXISTS mytable (id INTEGER PRIMARY KEY, mycolumn INTEGER DEFAULT (CAST(abs(random()) AS INTEGER)));
CREATE INDEX idx1 ON mytable(myColumn|9223372036854775806);
-- CREATE INDEX idx2 ON mytable(DISTINCT myColumn|9223372036854775806); CANNOT BE USED AS DISTINCT is syntax error.
-- CREATE INDEX idx3 ON mytable(myColumn) WHERE myColumn =  (SELECT DISTINCT myColumn|9223372036854775806 FROM mytable);
CREATE INDEX idx10 ON mytable(mycolumn) WHERE mycolumn < 9223372036854775806 / 10;
CREATE INDEX idx20 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 10 AND mycolumn < 9223372036854775806 / 20;
CREATE INDEX idx30 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 20 AND mycolumn < 9223372036854775806 / 30;
CREATE INDEX idx40 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 30 AND mycolumn < 9223372036854775806 / 40;
CREATE INDEX idx50 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 40 AND mycolumn < 9223372036854775806 / 50;
CREATE INDEX idx60 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 50 AND mycolumn < 9223372036854775806 / 60;
CREATE INDEX idx70 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 60 AND mycolumn < 9223372036854775806 / 70;
CREATE INDEX idx80 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 70 AND mycolumn < 9223372036854775806 / 80;
CREATE INDEX idx90 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 80 AND mycolumn < 9223372036854775806 / 90;
CREATE INDEX idx100 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 90;
/* Load some data */
WITH RECURSIVE cte(x,y) AS (
    SELECT 1,CAST(abs(random()) AS INTEGER)
    UNION ALL SELECT x+1,CAST(abs(random()) AS INTEGER) FROM cte LIMIT 1000000
)
INSERT INTO mytable (mycolumn) SELECT y FROM cte;

/* Show some sample data */
SELECT mycolumn,myColumn|9223372036854775806 AS x FROM mytable LIMIT 100;

/* LOOK AT WHAT THE QUERY PLANNER COMES UP WITH */
EXPLAIN QUERY PLAN
SELECT DISTINCT mycolumn,myColumn|9223372036854775806 AS x FROM mytable;
EXPLAIN QUERY PLAN
SELECT /*(SELECT count() FROM mytable) AS rows,*/*, mycolumn|9223372036854775806 AS x FROM mytable GROUP BY myColumn|9223372036854775806;


SELECT DISTINCT mycolumn,myColumn|9223372036854775806 AS x FROM mytable LIMIT 100;
SELECT /*(SELECT count() FROM mytable) AS rows,*/*, mycolumn|9223372036854775806 AS x FROM mytable GROUP BY myColumn|9223372036854775806;

EXPLAIN QUERY PLAN
SELECT mycolumn FROM mytable WHERE mycolumn < 9223372036854775806 / 10 LIMIT 100;

SELECT mycolumn FROM mytable WHERE mycolumn < 9223372036854775806 / 10 LIMIT 100;

/* CLEAN UP */
DROP TABLE IF EXISTS mytable;
DROP INDEX IF EXISTS idx1;
DROP INDEX IF EXISTS idx2;
DROP INDEX IF EXISTS idx10;
DROP INDEX IF EXISTS idx20;
DROP INDEX IF EXISTS idx30;
DROP INDEX IF EXISTS idx40;
DROP INDEX IF EXISTS idx50;
DROP INDEX IF EXISTS idx60;
DROP INDEX IF EXISTS idx70;
DROP INDEX IF EXISTS idx80;
DROP INDEX IF EXISTS idx90;
DROP INDEX IF EXISTS idx100;

DROP TABLE IF EXISTS mytable
> OK
> Time: 1.173s


DROP INDEX IF EXISTS idx1
> OK
> Time: 0s


DROP INDEX IF EXISTS idx2
> OK
> Time: 0s


DROP INDEX IF EXISTS idx10
> OK
> Time: 0s


DROP INDEX IF EXISTS idx20
> OK
> Time: 0s


DROP INDEX IF EXISTS idx30
> OK
> Time: 0s


DROP INDEX IF EXISTS idx40
> OK
> Time: 0s


DROP INDEX IF EXISTS idx50
> OK
> Time: 0s


DROP INDEX IF EXISTS idx60
> OK
> Time: 0s


DROP INDEX IF EXISTS idx70
> OK
> Time: 0s


DROP INDEX IF EXISTS idx80
> OK
> Time: 0s


DROP INDEX IF EXISTS idx90
> OK
> Time: 0s


DROP INDEX IF EXISTS idx100
> OK
> Time: 0s


CREATE TABLE IF NOT EXISTS mytable (id INTEGER PRIMARY KEY, mycolumn INTEGER DEFAULT (CAST(abs(random()) AS INTEGER)))
> OK
> Time: 0.056s


CREATE INDEX idx1 ON mytable(myColumn|9223372036854775806)
> OK
> Time: 0.024s


-- CREATE INDEX idx2 ON mytable(DISTINCT myColumn|9223372036854775806); CANNOT BE USED AS DISTINCT is syntax error.
-- CREATE INDEX idx3 ON mytable(myColumn) WHERE myColumn =  (SELECT DISTINCT myColumn|9223372036854775806 FROM mytable);
CREATE INDEX idx10 ON mytable(mycolumn) WHERE mycolumn < 9223372036854775806 / 10
> OK
> Time: 0.024s


CREATE INDEX idx20 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 10 AND mycolumn < 9223372036854775806 / 20
> OK
> Time: 0.024s


CREATE INDEX idx30 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 20 AND mycolumn < 9223372036854775806 / 30
> OK
> Time: 0.024s


CREATE INDEX idx40 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 30 AND mycolumn < 9223372036854775806 / 40
> OK
> Time: 0.024s


CREATE INDEX idx50 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 40 AND mycolumn < 9223372036854775806 / 50
> OK
> Time: 0.024s


CREATE INDEX idx60 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 50 AND mycolumn < 9223372036854775806 / 60
> OK
> Time: 0.024s


CREATE INDEX idx70 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 60 AND mycolumn < 9223372036854775806 / 70
> OK
> Time: 0.024s


CREATE INDEX idx80 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 70 AND mycolumn < 9223372036854775806 / 80
> OK
> Time: 0.024s


CREATE INDEX idx90 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 80 AND mycolumn < 9223372036854775806 / 90
> OK
> Time: 0.024s


CREATE INDEX idx100 ON mytable(mycolumn) WHERE mycolumn >= 9223372036854775806 / 90
> OK
> Time: 0.024s


/* Load some data */
WITH RECURSIVE cte(x,y) AS (
    SELECT 1,CAST(abs(random()) AS INTEGER)
    UNION ALL SELECT x+1,CAST(abs(random()) AS INTEGER) FROM cte LIMIT 1000000
)
INSERT INTO mytable (mycolumn) SELECT y FROM cte
> Affected rows: 1000000
> Time: 14.096s


/* Show some sample data */
SELECT mycolumn,myColumn|9223372036854775806 AS x FROM mytable LIMIT 100
> OK
> Time: 0.001s


/* LOOK AT WHAT THE QUERY PLANNER COMES UP WITH */
EXPLAIN QUERY PLAN
SELECT DISTINCT mycolumn,myColumn|9223372036854775806 AS x FROM mytable
> OK
> Time: 0s


EXPLAIN QUERY PLAN
SELECT /*(SELECT count() FROM mytable) AS rows,*/*, mycolumn|9223372036854775806 AS x FROM mytable GROUP BY myColumn|9223372036854775806
> OK
> Time: 0s


SELECT DISTINCT mycolumn,myColumn|9223372036854775806 AS x FROM mytable LIMIT 100
> OK
> Time: 0.001s


SELECT /*(SELECT count() FROM mytable) AS rows,*/*, mycolumn|9223372036854775806 AS x FROM mytable GROUP BY myColumn|9223372036854775806
> OK
> Time: 0.093s


EXPLAIN QUERY PLAN
SELECT mycolumn FROM mytable WHERE mycolumn < 9223372036854775806 / 10 LIMIT 100
> OK
> Time: 0s


SELECT mycolumn FROM mytable WHERE mycolumn < 9223372036854775806 / 10 LIMIT 100
> OK
> Time: 0s


/* CLEAN UP */
DROP TABLE IF EXISTS mytable
> OK
> Time: 0.793s


DROP INDEX IF EXISTS idx1
> OK
> Time: 0s


DROP INDEX IF EXISTS idx2
> OK
> Time: 0s


DROP INDEX IF EXISTS idx10
> OK
> Time: 0s


DROP INDEX IF EXISTS idx20
> OK
> Time: 0s


DROP INDEX IF EXISTS idx30
> OK
> Time: 0s


DROP INDEX IF EXISTS idx40
> OK
> Time: 0s


DROP INDEX IF EXISTS idx50
> OK
> Time: 0s


DROP INDEX IF EXISTS idx60
> OK
> Time: 0s


DROP INDEX IF EXISTS idx70
> OK
> Time: 0s


DROP INDEX IF EXISTS idx80
> OK
> Time: 0s


DROP INDEX IF EXISTS idx90
> OK
> Time: 0s


DROP INDEX IF EXISTS idx100
> OK
> Time: 0s