Postgresql - Count number of instances of substring in results of ILIKE query - sql

Question

I have a query like this, that returns rows of text that match the given query:
SELECT content
FROM messages
WHERE created_at >= '2021-07-24T20:17:18.141Z'
AND created_at <= '2021-07-31T20:11:20.542Z'
AND content ILIKE '%Search Term%';
Right now, if I just count the rows, it just returns the number of messages with that search term. However, I'd like to count the number of Instances of the search term, rather than the number of Rows that contain the search term.
I thought of making a stored function that looped through the results of the above function and counted the instances. But it ended up being insanely slow. I’m okay with it being pretty slow, but is there a solution to this that either runs slightly faster or doesn’t require a function?

Answer 1

Try this:
SELECT
SUM(
CASE
WHEN content ILIKE '%Search Term%' THEN 1
ELSE 0
END
)
FROM
messages
WHERE
created_at >= '2021-07-24T20:17:18.141Z' AND
created_at <= '2021-07-31T20:11:20.542Z';

Answer 2

You can use regexp_matches():
select count(*)
from messages m cross join lateral
regexp_matches(m.content, $search_string, 'g')
Note: This assumes that $search_string doesn't contain regular expression special characters.
If you want the count on each row, you can use:
select m.*,
(select count(*)
from regexp_matches(m.content, $search_string, 'g')
) as num_matches
from messages m;

Answer 3

Now I understood your question properly. You can use regexp_matches() in substring to get what you want.
select content,(SELECT count(*) FROM regexp_matches(content, 'Search Term', 'g')) search_count
FROM messages
WHERE created_at >= '2021-07-24T20:17:18.141Z'
AND created_at <= '2021-07-31T20:11:20.542Z'
AND content ILIKE '%Search Term%';
** The 'g' flag repeats multiple matches on a string.