Mark Mielke wrote:
> Simon Riggs wrote:
>> ISTM we would be able to do this fairly well if we implemented
>> Index-only columns. i.e. columns that don't exist in the heap, only in
>> an index.
>> Taken to the extreme, all columns could be removed from the heap and
>> placed in an index(es). Only the visibility information would remain on
>> the heap.
>>
> Wouldn't the extreme be - even the visibility information is in the index?
Maybe we could extract the visibility information and put it in a
storage separate from the heap. A seqscan would be a bit slower (have
to check the heap and the visibility storage) but some index scans could
be faster (can check the index and visibility storage, skipping the
heap), and updates would be faster too (append into the heap, update
visibility storage). This would allow something closer to index-only
scans. Of course, the key is to allow efficient lookup of visibility
info given a TID.
Has this been explored before?
--
Alvaro Herrera http://www.CommandPrompt.com/
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