函数索引引用的函数必须是immutable类型
作者:互联网
用户在使用中,可能会用到基于函数的索引,但是函数是非 immutable 类型的,导致函数索引无法创建。如:
test=# create index ind_t1 on t1(to_char(create_date,'yyyy-mm')); ERROR: functions in index expression must be marked IMMUTABLE
这里我们先看下函数的类型:
test=# \df+ to_char List of functions Schema | Name | Result data type | Argument data types | Type | Volatility | Parallel | Owner | Security | Access privileges | Language | Source code | Description ------------+---------+------------------+-----------------------------------+------+------------+----------+--------+----------+-------------------+----------+---------------------------------+----------------------------------------- pg_catalog | to_char | text | bigint, text | func | stable | safe | system | invoker | | internal | int8_to_char | format int8 to text pg_catalog | to_char | text | double precision, text | func | stable | safe | system | invoker | | internal | float8_to_char | format float8 to text pg_catalog | to_char | text | integer, text | func | stable | safe | system | invoker | | internal | int4_to_char | format int4 to text pg_catalog | to_char | text | interval, text | func | stable | safe | system | invoker | | internal | interval_to_char | format interval to text pg_catalog | to_char | text | numeric, text | func | stable | safe | system | invoker | | internal | numeric_to_char | format numeric to text pg_catalog | to_char | text | real, text | func | stable | safe | system | invoker | | internal | float4_to_char | format float4 to text pg_catalog | to_char | text | timestamp without time zone, text | func | stable | safe | system | invoker | | internal | timestamp_to_char | format timestamp to text pg_catalog | to_char | text | timestamp with time zone, text | func | stable | safe | system | invoker | | internal | timestamptz_to_char | format timestamp with time zone to text pg_catalog | to_char | text | tinyint | func | immutable | safe | system | invoker | | sql | select cast($1 as text) | convert tinyint to text pg_catalog | to_char | text | tinyint, text | func | stable | safe | system | invoker | | c | tinyint_to_char | format tinyint to text sys | to_char | text | bigint | func | immutable | safe | system | invoker | | sql | select to_char($1::text); | sys | to_char | text | boolean | func | stable | unsafe | system | invoker | | sql | select cast($1 as text); +| | | | | | | | | | | | | sys | to_char | text | boolean, text | func | stable | unsafe | system | invoker | | sql | select text($1); +| | | | | | | | | | | | | sys | to_char | text | integer | func | immutable | safe | system | invoker | | sql | select to_char($1::text); | sys | to_char | text | smallint | func | immutable | safe | system | invoker | | sql | select to_char($1::text); | sys | to_char | text | text | func | immutable | safe | system | invoker | | plpgsql | +| | | | | | | | | | | | begin +| | | | | | | | | | | | return $1; +| | | | | | | | | | | | end; | sys | to_char | text | text, text | func | immutable | safe | system | invoker | | sql | select to_char($1::numeric,$2); | sys | to_char | text | timestamp without time zone | func | immutable | safe | system | invoker | | c | ora_to_char_timestamp | Convert timestamp to string (18 rows)
我们在看下对象的数据类型:
test=# \d t1 Table "public.t1" Column | Type | Collation | Nullable | Default -------------+---------+-----------+----------+--------- id | integer | | | create_date | date | | |
可以看到对象的 类型是date,再根据date类型寻找具体的to_char 函数,并修改为immutable
test=# alter function to_char(timestamp without time zone, text) immutable; ALTER FUNCTION
再创建索引:
test=# create index ind_t1 on t1(to_char(create_date,'yyyy-mm')); CREATE INDEX
标签:函数,text,safe,system,char,索引,invoker,func,immutable 来源: https://www.cnblogs.com/kingbase/p/15252109.html