Wrapping a where clause to preserve rows with nulls
| От | Adrian Garcia Badaracco |
|---|---|
| Тема | Wrapping a where clause to preserve rows with nulls |
| Дата | |
| Msg-id | CAE8z92GN0-5J=4q6RSsPGk_OP-Y_EHVNgQimTWwcq+BE+HGqRQ@mail.gmail.com обсуждение исходный текст |
| Ответы |
Re: Wrapping a where clause to preserve rows with nulls
Re: Wrapping a where clause to preserve rows with nulls |
| Список | pgsql-general |
I have a query where I have to run a where clause generated by another system (i.e., I can't modify that where clause. The where clause may return `null`, but I actually want to keep rows that return `null` (and rows that return `true` but not rows that return `false`).
I thought it would be as simple as wrapping in `(...) is not false` but that seems to prevent index usage.
For example, let's say that given the table:
CREATE TABLE test_index (value INTEGER);
CREATE INDEX idx_value ON test_index(value);
CREATE INDEX idx_value ON test_index(value);
And the predicate `value = 5000`, if I run the original query that excludes rows where the predicate is null it uses the index:
SELECT *
FROM test_index
WHERE value = 5000;
But as soon as I tack on an `IS NOT FALSE` the index is not used:
SELECT *
FROM test_index
WHERE (value = 5000) IS NOT FALSE;
This was surprising to me. I was hoping this might be able to use the index.
Is there any way to include the rows where the predicate evaluates to null while still using an index?
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