Get a Rails record count without quering a 2nd time

Question

I've got a Rails ActiveRecord query that find all the records where the name is some token.

records = Market.where("lower(name) = ?", name.downcase );
rec = records.first;
count = records.count;

The server shows that the calls for .first and .count were BOTH hitting the database.

←[1m←[35mCACHE (0.0ms)←[0m  SELECT "markets".* FROM "markets" WHERE (lower(nam
e) = 'my market') LIMIT 1

←[1m←[36mCACHE (0.0ms)←[0m  ←[1mSELECT COUNT(*) FROM "markets" WHERE (lower(na
me) = 'my market')←[0m

Why is it going to the database to get the count when it can use the results already queried?

I'm concerned about future performance. Today there are 1000 records. When that table holds 8 million rows, doing two queries one for data, and one for count, it will be expensive.

How do I get the count from the collection, not the database?

Answer 1

RactiveRecord use lazy query to fetch data from database. If you want to simple count the records, you can only call size of the retrun array.

records = Market.where("lower(name) = ?", name.downcase ).all
records.size