postgresql Postgres 中的位掩码
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Bit masking in Postgres
提问by Silviu Postavaru
I have this query
我有这个查询
SELECT * FROM "functions" WHERE (models_mask & 1 > 0)
and the I get the following error:
我收到以下错误：
PGError: ERROR: operator does not exist: character varying & integer
HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.
PGError：错误：运算符不存在：字符可变和整数
提示：没有运算符匹配给定的名称和参数类型。您可能需要添加显式类型转换。
The models_mask is an integer in the database. How can I fix this.
models_mask 是数据库中的整数。我怎样才能解决这个问题。
Thank you!
谢谢！
回答by Evan Carroll
Check out the docs on bit operatorsfor Pg.
Essentially &only works on two like types (usually bit or int), so model_maskwill have to be CASTed from varchar to something reasonable like bit or int:
基本上&只适用于两种类似的类型（通常是 bit 或 int），所以model_mask必须CAST从 varchar 编辑为合理的东西，比如 bit 或 int：
models_mask::int & 1-or- models_mask::int::bit & b'1'
models_mask::int & 1- 或-models_mask::int::bit & b'1'
You can find out what types an operator works with using \doSin psql
你可以找出哪些类型的运营商工作使用\doS中psql
pg_catalog | & | bigint | bigint | bigint | bitwise and
pg_catalog | & | bit | bit | bit | bitwise and
pg_catalog | & | inet | inet | inet | bitwise and
pg_catalog | & | integer | integer | integer | bitwise and
pg_catalog | & | smallint | smallint | smallint | bitwise and
Here is a quick example for more information
这是一个快速示例以获取更多信息
# SELECT 11 & 15 AS int, b'1011' & b'1111' AS bin INTO foo;
SELECT
# \d foo
Table "public.foo"
Column | Type | Modifiers
--------+---------+-----------
int | integer |
bin | "bit" |
# SELECT * FROM foo;
int | bin
-----+------
11 | 1011
