Subject | records identifiers |
---|---|
Author | danyschaer |
Post date | 2008-07-04T11:56:49Z |
Hi all;
There is a document at IBPhoenix, with title "A talk given by Ann
Harrison at the Open Source Database Conference in Tokyo, Japan,
February 2002" that says:
"Nor does Firebird have any record placement within a table. Other
databases cluster records based on an indexed value, so that records
likely to be read together are stored together. Access on any other
index is significantly slower. Firebird's indexed access is
structured differently. When a where clause can be resolved with an
index, Firebird first finds the identifiers of all the matching
records and stores them in a sparse bitmap (3). Because the bitmap is
ordered by record identifier and the record identifier reflects the
storage location of the record, all records on any particular page
will be read at once. The result is even lookup times on all indexes."
Me question are two:
1. Having a table, how can I retrieve that "record identifiers"?
2. Having a large list of records identifiers, how do I select all at
once?.
Best regards;
Dany
There is a document at IBPhoenix, with title "A talk given by Ann
Harrison at the Open Source Database Conference in Tokyo, Japan,
February 2002" that says:
"Nor does Firebird have any record placement within a table. Other
databases cluster records based on an indexed value, so that records
likely to be read together are stored together. Access on any other
index is significantly slower. Firebird's indexed access is
structured differently. When a where clause can be resolved with an
index, Firebird first finds the identifiers of all the matching
records and stores them in a sparse bitmap (3). Because the bitmap is
ordered by record identifier and the record identifier reflects the
storage location of the record, all records on any particular page
will be read at once. The result is even lookup times on all indexes."
Me question are two:
1. Having a table, how can I retrieve that "record identifiers"?
2. Having a large list of records identifiers, how do I select all at
once?.
Best regards;
Dany