Postgres位掩码中的"1"总数

Question

有没有办法在Postgres"位串"类型中获得1的总数？

Answer 1

# select length(replace(x::text, '0', '')) from ( values ('1010111101'::bit varying) ) as something(x);
 length
--------
      7
(1 row)

没有字符串转换的方法:

# select count(*) from ( select x, generate_series(1, length(x)) as i from ( values ('1010111101'::bit varying) ) as something(x) ) as q where substring(x, i, 1) = B'1';
 count
-------
     7
(1 row)

Answer 2

如果您需要它真正高效，请进行以下讨论：Efficiently certaining the number of bits set in thecontents of, a VARBIT field