mirror of
https://github.com/postgres/postgres.git
synced 2026-02-19 02:29:10 -05:00
54111e9511
threshold for tuple length. On 4-byte-MAXALIGN machines, the toast code creates tuples that have t_len exactly TOAST_TUPLE_THRESHOLD ... but this number is not itself maxaligned, so if heap_insert maxaligns t_len before comparing to TOAST_TUPLE_THRESHOLD, it'll uselessly recurse back to tuptoaster.c, wasting cycles. (It turns out that this does not happen on 8-byte-MAXALIGN machines, because for them the outer MAXALIGN in the TOAST_MAX_CHUNK_SIZE macro reduces TOAST_MAX_CHUNK_SIZE so that toast tuples will be less than TOAST_TUPLE_THRESHOLD in size. That MAXALIGN is really incorrect, but we can't remove it now, see below.) There isn't any particular value in maxaligning before comparing to the thresholds, so just don't do that, which saves a small number of cycles in itself. These numbers should be rejiggered to minimize wasted space on toast-relation pages, but we can't do that in the back branches because changing TOAST_MAX_CHUNK_SIZE would force an initdb (by changing the contents of toast tables). We can move the toast decision thresholds a bit, though, which is what this patch effectively does. Thanks to Pavan Deolasee for discovering the unintended recursion. Back-patch into 8.2, but not further, pending more testing. (HEAD is about to get a further patch modifying the thresholds, so it won't help much for testing this form of the patch.) |
||
|---|---|---|
| .. | ||
| access | ||
| bootstrap | ||
| catalog | ||
| commands | ||
| executor | ||
| lib | ||
| libpq | ||
| mb | ||
| nodes | ||
| optimizer | ||
| parser | ||
| port | ||
| postmaster | ||
| regex | ||
| rewrite | ||
| storage | ||
| tcop | ||
| utils | ||
| c.h | ||
| fmgr.h | ||
| funcapi.h | ||
| getaddrinfo.h | ||
| getopt_long.h | ||
| Makefile | ||
| miscadmin.h | ||
| pg_config.h.in | ||
| pg_config.h.win32 | ||
| pg_config_manual.h | ||
| pg_trace.h | ||
| pgstat.h | ||
| pgtime.h | ||
| port.h | ||
| postgres.h | ||
| postgres_ext.h | ||
| postgres_fe.h | ||
| rusagestub.h | ||