Xiao Meng wrote:
Hi, hackers.
I'm working on my gsoc project - improving hash index.
I need to create a TupldeDesc with uint32 attribute.
Here is the reason why I need it -
If we store hash code only in the tuple, then the TupleDesc's
attribute should be uint32
Something along the lines of:
TupleDesc tupdesc = CreateTemplateTupleDesc(1, false);
TupleDescInitEntry(tupdesc, 1, "hashcode", INT4OID, -1, 0);
In this way, we can use index_form_tuple() to create a tuple and
needn't write a function for hash specially.
I would actually suggest ditching the normal page layout with line
pointers and IndexTuples altogether. All the entries are fixed size, so
you can get away with a much simpler structure, and store more entries
per page. Storing an IndexTuple with one int32 column takes
(sizeof(IndexTupleData) + sizeof(uint32) + sizeof(ItemIdData)) = 16 bytes,
but you only need a pointer to the heap tuple, and the hash code, which
is just 10 bytes in total. Or 12 if you have to align the hash code to 4
byte boundary.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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