Re: Tsearch Index Size and GiST vs. GIN

Richard Whidden wrote:
> Due to popular demand (1 person), I've compared sizes with 90 and 100
> fillfactors, along with using the new GIN index.

First, GIN doesn't utilize fillfactor option yet.

>
> Findings were not surprising, except for the GIN indexes, which doubled
> in size.
Second, In opposite to GiST, size of GIN index strongly depends on document
collection. Each unique word in collection has list of pointer to document in
which it occur. Size of pointer is a 6 byte. So word with 4 bytes length will
occupy at least 4 + N_docs_with_word * 6.

Fortunately, for searching it's needed to read very small part of index, so GIN
will be faster.

>
> After several ALTER/RE INDEXes, here they are:
>
> GiST
> ----
> 8.1 = 94990
> 8.2 FF90 = 106244 relpages (8k)
> 8.2 FF100 = 95049
>
> GIN
> ---
> FF100 = 197702
>
>
> Richard Whidden
>
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Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru
WWW: http://www.sigaev.ru/