diff options
| author | Peter Geoghegan | 2019-08-14 00:16:44 +0000 |
|---|---|---|
| committer | Peter Geoghegan | 2019-08-14 00:16:44 +0000 |
| commit | 68ef887842ff716097bbb1bad86a40bb62247061 (patch) | |
| tree | cb68c237ea705af995a5107c28a845c001cb993d /src/backend/access/nbtree/README | |
| parent | 31d43710fb069a5c2be6ec1dbc9fa7261cf9feff (diff) | |
Remove obsolete nbtree README commentary.
Commit d2086b08b02 removed almost all cases where nbtree must release a
read buffer lock and acquire a write buffer lock instead, so remaining
cases in which that's still necessary are not notable enough to appear
in the nbtree README.
More importantly, holding on to a buffer pin in cases where nbtree must
trade a read lock for a write lock is very unlikely to save any I/O.
This seems to have been a long overlooked throwback to a time when
nbtree cared about write-ordering dependencies, and performed
synchronous buffer writes. It hasn't worked that way in many years.
Diffstat (limited to 'src/backend/access/nbtree/README')
| -rw-r--r-- | src/backend/access/nbtree/README | 5 |
1 files changed, 1 insertions, 4 deletions
diff --git a/src/backend/access/nbtree/README b/src/backend/access/nbtree/README index 3d01b7854df..dce8bc98e93 100644 --- a/src/backend/access/nbtree/README +++ b/src/backend/access/nbtree/README @@ -65,10 +65,7 @@ copies of tree pages are unshared. Postgres shares in-memory buffers among backends. As a result, we do page-level read locking on btree pages in order to guarantee that no record is modified while we are examining it. This reduces concurrency but guarantees correct -behavior. An advantage is that when trading in a read lock for a -write lock, we need not re-read the page after getting the write lock. -Since we're also holding a pin on the shared buffer containing the -page, we know that buffer still contains the page and is up-to-date. +behavior. We support the notion of an ordered "scan" of an index as well as insertions, deletions, and simple lookups. A scan in the forward |