Indexing affects only the WHERE clause?
- by andre matos
If I have something like:
CREATE INDEX idx_myTable_field_x
ON myTable
USING btree (field_x);
SELECT COUNT(field_x), field_x FROM myTable GROUP BY field_x ORDER BY field_x;
Imagine myTable with around 500,000 rows and most of field_x values being unique.
Since I don't use any WHERE clause, will the created index have any effect at all in my query?
Edit: I'm asking this question because I don't get any relevant difference between query-times before and after creating the index; They always take about 8 seconds (which, of course is too much time!). Is this behaviour expected?
