Re: Searching GIN-index (FTS) and sort by timestamp-column

> On 16 Mar 2016, at 17:52, Evgeniy Shishkin <itparanoia(at)gmail(dot)com> wrote:
>
>
>> On 16 Mar 2016, at 16:37, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>
>> Andreas Joseph Krogh <andreas(at)visena(dot)com> writes:
>>> 1. Why isnt' folder_id part of the index-cond?
>>
>> Because a GIN index is useless for sorting.
>
> I don't see how gin inability to return sorted data relates to index condition.
> In fact i tried to reproduce the example,
> and if i change folder_id to int from bigint, then index condition with folder_id is used
>
> Index Cond: ((fts_all @@ '''hi'''::tsquery) AND (folder_id = 1))
>

Looks like documentation http://www.postgresql.org/docs/9.5/static/btree-gin.html
is lying about supporting int8 type

>
>>
>>> 2. Is there a way to make it use the (same) index to sort by
>>> received_timestamp?
>>
>> No.
>>
>>> 3. Using a GIN-index, is there a way to use the index at all for sorting?
>>
>> No.
>>
>>> 4. It doesn't seem like ts_rank uses the index for sorting either.
>>
>> Same reason.
>>
>> regards, tom lane
>>
>>
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>