From: | John Frank <jrf(at)segovia(dot)mit(dot)edu> |
---|---|
To: | <pgsql-general(at)postgresql(dot)org> |
Subject: | HASH: Out of overflow pages. Out of luck. |
Date: | 2001-01-24 02:54:41 |
Message-ID: | Pine.LNX.4.30.0101232117340.5180-100000@segovia.mit.edu |
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Lists: | pgsql-general |
Does anyone have experience hacking the HASH index code to allow more
overflow pages?
I get the following when indexing a table with about 300M entries:
db=# \d table1
Table "table1"
Attribute | Type | Modifier
-----------+--------------+----------
field1 | varchar(256) |
field2 | integer |
field3 | float8 |
db=# create index table1_field1 on table1 using hash(field1);
ERROR: HASH: Out of overflow pages. Out of luck.
This also happens for field2.
I looked in the source for postgresql-7.0.3 from
src/include/access/hash.h:
* The reason that the size is restricted to NCACHED (32) is because
* the bitmaps are 16 bits: upper 5 represent the splitpoint, lower 11
* indicate the page number within the splitpoint. Since there are
* only 5 bits to store the splitpoint, there can only be 32 splitpoints.
* Both spares[] and bitmaps[] use splitpoints as there indices, so there
* can only be 32 of them.
*/
#define NCACHED 32
Is there a way around this?! If not: what a horrific limitation.
Thanks! John
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