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Small fixes

This commit is contained in:
Teodor Sigaev 2005-09-16 14:40:54 +00:00
parent 3f558e3dae
commit f4516f8732
1 changed files with 10 additions and 8 deletions
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18
src/backend/access/gist/README
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@ -1,4 +1,4 @@
$PostgreSQL: pgsql/src/backend/access/gist/README,v 1.2 2005/09/15 17:44:27 neilc Exp $
$PostgreSQL: pgsql/src/backend/access/gist/README,v 1.3 2005/09/16 14:40:54 teodor Exp $
This directory contains an implementation of GiST indexing for Postgres.
@ -21,7 +21,9 @@ The current implementation of GiST supports:
* Concurrency
* Recovery support via WAL logging
The support for concurrency implemented in PostgreSQL was developed based on the paper "Access Methods for Next-Generation Database Systems" by Marcel Kornaker:
The support for concurrency implemented in PostgreSQL was developed based on
the paper "Access Methods for Next-Generation Database Systems" by
Marcel Kornaker:
http://www.sai.msu.su/~megera/postgres/gist/papers/concurrency/access-methods-for-next-generation.pdf.gz
@ -31,11 +33,11 @@ The original algorithms were modified in several ways:
algorithm was considerably changed, because in PostgreSQL function search
should return one tuple (next), not all tuples at once. Also, it should
release page locks between calls.
* Since we added support for variable length keys, it's not possible to guarantee
enough free space for all keys on pages after splitting. User defined function
picksplit doesn't have information about size of tuples (each tuple may
contain several keys as in multicolumn index while picksplit could work with
only one key) and pages.
* Since we added support for variable length keys, it's not possible to
guarantee enough free space for all keys on pages after splitting. User
defined function picksplit doesn't have information about size of tuples
(each tuple may contain several keys as in multicolumn index while picksplit
could work with only one key) and pages.
* We modified original INSERT algorithm for performance reason. In particular,
it is now a single-pass algorithm.
* Since the papers were theoretical, some details were omitted and we
@ -197,7 +199,7 @@ placetopage(page, keysarray)
if ( no space left on page )
keysarray = pageSplit(page, [ extract_keys(page), keysarray])
last page in chain gets old NSN,
original and others - new NSN from current LSN
original and others - new NSN equals to LSN
if ( page is root )
make new root with keysarray
end