From 4adc2f72a4ccd6e55e594aca837f09130a6af62b Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 15 Sep 2008 18:43:41 +0000 Subject: Change hash indexes to store only the hash code rather than the whole indexed value. This means that hash index lookups are always lossy and have to be rechecked when the heap is visited; however, the gain in index compactness outweighs this when the indexed values are wide. Also, we only need to perform datatype comparisons when the hash codes match exactly, rather than for every entry in the hash bucket; so it could also win for datatypes that have expensive comparison functions. A small additional win is gained by keeping hash index pages sorted by hash code and using binary search to reduce the number of index tuples we have to look at. Xiao Meng This commit also incorporates Zdenek Kotala's patch to isolate hash metapages and hash bitmaps a bit better from the page header datastructures. --- doc/src/sgml/catalogs.sgml | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) (limited to 'doc/src') diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml index 97a624f453e..646e37d79fc 100644 --- a/doc/src/sgml/catalogs.sgml +++ b/doc/src/sgml/catalogs.sgml @@ -1,4 +1,4 @@ - + @@ -451,6 +451,13 @@ Can an index of this type be clustered on? + + amkeytype + oid + pg_type.oid + Type of data stored in index, or zero if not a fixed type + + aminsert regproc @@ -6424,7 +6431,7 @@ sourceline text - Line number within the sourcefile the current value was set + Line number within the sourcefile the current value was set from (NULL for values set in sources other than configuration files) -- cgit v1.2.3