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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2007-09-05 18:10:48 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2007-09-05 18:10:48 +0000 |
| commit | 295e63983d7596ccc5717ff4a0a235ba241a2614 (patch) | |
| tree | d4d8baaed4992dab3a4ae5110f765237da136cb3 /src/backend/utils/misc/postgresql.conf.sample | |
| parent | 2e74c53ec1103f92c5704d87a4af2ab573402212 (diff) | |
| download | postgresql-295e63983d7596ccc5717ff4a0a235ba241a2614.tar.gz | |
Implement lazy XID allocation: transactions that do not modify any database
rows will normally never obtain an XID at all. We already did things this way
for subtransactions, but this patch extends the concept to top-level
transactions. In applications where there are lots of short read-only
transactions, this should improve performance noticeably; not so much from
removal of the actual XID-assignments, as from reduction of overhead that's
driven by the rate of XID consumption. We add a concept of a "virtual
transaction ID" so that active transactions can be uniquely identified even
if they don't have a regular XID. This is a much lighter-weight concept:
uniqueness of VXIDs is only guaranteed over the short term, and no on-disk
record is made about them.
Florian Pflug, with some editorialization by Tom.
Diffstat (limited to 'src/backend/utils/misc/postgresql.conf.sample')
| -rw-r--r-- | src/backend/utils/misc/postgresql.conf.sample | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index b22099c2fd..7de3145aa0 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -338,7 +338,8 @@ # %c = session id # %l = session line number # %s = session start timestamp - # %x = transaction id + # %v = virtual transaction id + # %x = transaction id (0 if none) # %q = stop here in non-session # processes # %% = '%' |