The reality is that most PostgreSQL configuration parameters don’t have a huge impact on overall system performance. There are, however, a couple that really can make a huge difference when tuned from the defaults. work_mem is one of them, and max_wal_size is another.
max_wal_size controls how large the write-ahead log can get on disk before PostgreSQL does a checkpoint.
If you google around for how to set work_mem in PostgreSQL, you’ll probably find something like:
To set work_mem, take the number of connections, add 32, divide by your astrological sign expressed as a number (Aquarius is 1), convert it to base 7, and then read that number in decimal megabytes.
Over the course of the last few versions, PostgreSQL has introduces all kinds of background worker processes, including workers to do various kinds of things in parallel. There are enough now that it’s getting kind of confusing. Let’s sort them all out.
You can think of each setting as creating a pool of potential workers. Each setting draws its
Normally, when you drop a column from PostgreSQL, it doesn’t have to do anything to the data in the table. It just marks the column as no longer alive in the system catalogs, and gets on with business.
There is, however, a big exception to this: ALTER TABLE … SET WITHOUT OIDS. This pops up when using pg_upgrade