Why does PostgresQL query performance drop over time, but restored when rebuilding index

Question

According to this page in the manual, indexes don\'t need to be maintained. However, we are running with a PostgresQL table that has a continuous rate of upd

Answer 1

As for performance, using strings for storing time and status info is quite a bottleneck. First of all, indexes on texts are extremely inefficient, comparing two times on the same day needs at least 11 comparison (in the format you used), however, using time type it can be reduced to simply one comparison. This also effects the size of the index, and a large index is hard to search over, and the db won't keep it in memory. Same considerations apply to the state column. If it represents a small set of states, you should use integer numbers mapped to states, this will reduce the nodes of the index - and the index size accordingly. Furthermore, this index will be useless even using theese built-in types if you don't specify the actual time in your query.