在PostgreSQL中将位字符串转换为数组

Question

我有一个160个字符串的字符串,我需要一个整数数组来存储值为1的位的位置.

例:

bitstring = '00110101'
array = [3,4,6,8]

是否可以仅使用SQL执行此操作,还是需要定义PL/SQL函数或类似的东西？

Answer 1

确实可以用SQL编写它.这是一个起点:

select array(
  select substring(str from i for 1) as bit
  from generate_series(1, length(str)) as i
  where bit = '1'
);

不过,您可能希望将其包装在pl/sql函数中,以避免在整个地方重复代码.

工作功能:

create or replace function get_bit_positions(varbit) returns bit[] as $$
select array(
  select substring($1 from i for 1) as bit
  from generate_series(1, length($1)) as i
  where substring($1 from i for 1) = '1'
);
$$ language sql immutable;

Answer 2

工作版本:

WITH x AS (SELECT '00110101'::varbit AS b)
SELECT array_agg(i)
FROM  (SELECT b, generate_series(1, length(b)) AS i FROM x) y
WHERE  substring(b, i, 1) = '1';

更简单,一旦你转换varbit到text[].投奔text并运行string_to_array().

然后你可以generate_subscripts()按索引使用和选择数组元素:

WITH x AS (SELECT string_to_array('00110101'::varbit::text, NULL) AS b)
SELECT array_agg(i)
FROM  (SELECT b, generate_subscripts(b,1) AS i FROM x) y
WHERE b[i] = '1'

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