Shaun Thomas: Burnt Toast

In a pgedge.com post, Shaun Thomas revisits a slow Postgres event_log table whose large XML column he had long blamed on TOAST. In a 100k-row JSON test, the toasted table was 47 MB against 318 MB untoasted, and counting rows took 26 ms versus 91 ms, though reading the toasted column itself was slower. Moving the column to a separate table cut the main heap to 5 MB. lz4 compressed over 30 times faster than pglz, with about 20% slower decompression. These are single-author tests on one synthetic workload.