Hi Igor:
On Mon, Jul 20, 2015 at 4:56 PM, Igor Neyman <ineyman@xxxxxxxxxxxxxx> wrote:
> Well, there is a caveat.
> If I create table and couple indexes like this:
..
> and populate them:
> and then check the size of the indexes:
> for "select pg_relation_size('U1')" I get 2834432
> while " select pg_relation_size('U2')" returns 2285568.
> So, index based on randomly populated column is bigger than the one based on sequentially populated.
> But, on the other hand, after:
> reindex table test_index_size;
> both indexes are of the same size: 2260992.
I would totally expect this. On reindex you get the values from a tree
walk, so both of them come in order, and being a reindex ( where you
know in advance the full set of values, so you can plan ahead where to
put the leaves, how many levels you need and how many splits ) you get
an even bigger advantage from the squential insertion case.
Francisco Olarte.
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