The above wiki states that "if a query involves doing merge sorts of 8 tables, that requires 8 times work_mem." If I have a table that is partitioned does each partition count as a "table" and get its on work_mem?
For example, say I have the following table partitioned by the time column:
CREATE TABLE values (time TIMESTAMP, value INTEGER);
If I do the following query will it require 1 work_mem or N work_mem's (where N is the number of partitions)?
SELECT * FROM values ORDER BY time;
The specific query you show should do the append first and then the sort on the result, and so would only use 1 work_mem.
However, other queries could cause it to use one (or more) sorts per partition, for example a self-join which it decides to run as a sort-merge join.
