I am not sure if this applies only to clustering but for storage in general,
IIRC Oracle has 2 parameters that can be set at table creation : from Oracle docs
PCTFREE integer :
Specify the percentage of space in each data block of the table, object table OID index, or partition reserved for future updates to the table's rows. The value of PCTFREE must be a value from 0 to 99. A value of 0 allows the entire block to be filled by inserts of new rows. The default value is 10. This value reserves 10% of each block for updates to existing rows and allows inserts of new rows to fill a maximum of 90% of each block.
PCTFREE has the same function in the PARTITION description and in the statements that create and alter clusters, indexes, materialized views, and materialized view logs. The combination of PCTFREE and PCTUSED determines whether new rows will be inserted into existing data blocks or into new blocks.
Specify the minimum percentage of used space that Oracle maintains for each data block of the table, object table OID index, or index-organized table overflow data segment. A block becomes a candidate for row insertion when its used space falls below PCTUSED. PCTUSED is specified as a positive integer from 0 to 99 and defaults to 40.
PCTUSED has the same function in the PARTITION description and in the statements that create and alter clusters, materialized views, and materialized view logs.
PCTUSED is not a valid table storage characteristic for an index-organized table (ORGANIZATION INDEX).
The sum of PCTFREE and PCTUSED must be equal to or less than 100. You can use PCTFREE and PCTUSED together to utilize space within a table more efficiently.
PostgreSQL could take some hints from the above.
On Aug 27, 2004, at 1:26 AM, Gaetano Mendola wrote:
Greg Stark wrote:
The discussions before talked about a mechanism to try to place new> tuples as close as possible to the proper index position.
Means this that an index shall have a "fill factor" property, similar to
Informix one ?
From the manual:
The FILLFACTOR option takes effect only when you build an index on a table
that contains more than 5,000 rows and uses more than 100 table pages, when
you create an index on a fragmented table, or when you create a fragmented
index on a nonfragmented table.
Use the FILLFACTOR option to provide for expansion of an index at a later
date or to create compacted indexes.
When the index is created, the database server initially fills only that
percentage of the nodes specified with the FILLFACTOR value.
# Providing a Low Percentage Value
If you provide a low percentage value, such as 50, you allow room for growth
in your index. The nodes of the index initially fill to a certain percentage and
contain space for inserts. The amount of available space depends on the
number of keys in each page as well as the percentage value.
For example, with a 50-percent FILLFACTOR value, the page would be half
full and could accommodate doubling in size. A low percentage value can
result in faster inserts and can be used for indexes that you expect to grow.
# Providing a High Percentage Value
If you provide a high percentage value, such as 99, your indexes are
compacted, and any new index inserts result in splitting nodes. The
maximum density is achieved with 100 percent. With a 100-percent
FILLFACTOR value, the index has no room available for growth; any
additions to the index result in splitting the nodes.
A 99-percent FILLFACTOR value allows room for at least one insertion per
node. A high percentage value can result in faster selects and can be used for
indexes that you do not expect to grow or for mostly read-only indexes.
Regards Gaetano Mendola
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