Solr search performance

sean mcevoy sean.mcevoy at gmail.com
Mon Sep 19 16:48:54 EDT 2016


Hi All,

We have an index with ~548,000 entries, ~14,000 of which match one of our
queries.
We read these in a paginated search and the first page (of 100 hits)
returns quickly in ~70ms.
This response time seems to increase exponentially as we walk through the
pages:
the 4th page takes ~200ms,
the 8th page takes ~1200ms
the 12th page takes ~2100ms
the 16th page takes ~6100ms
the 20th page takes ~24000ms

And by the time we're searching for the 22nd page it regularly times out at
the default 60 seconds.

I have a good unsderstanding of riak KV internals but absolutely nothing of
Lucene which I think is what's most relevant here. If anyone in the know
can point me towards any relevant resource or can explain what's happening
I'd be much obliged :-)
As I would also be if anyone with experience of using Riak/Lucene can tell
me:
- Is 500K a crazy number of entries to put into one index?
- Is 14K a crazy number of entries to expect to be returned?
- Are there any methods we can use to make the search time more constant
across the full search?
I read one blog post on inlining but it was a bit old & not very obvious
how to implement using riakc_pb_socket calls.

And out of curiosity, do we not traverse the full range of hits for each
page? I naively thought that because I'm sorting the returned values we'd
have to get them all first and then sort, but the response times suggests
otherwise. Does Lucene store the data sorted by each field just in case a
query asks for it? Or what other magic is going on?


For the technical details, we use the "_yz_default" schema and all the
fields stored are strings:
- entry_id_s: unique within the DB, the aim of the query is to gather a
list of these
- type_s: has one of 2 values
- sub_category_id_s: in the query described above all 14K hits will match
on this, in the DB of ~500K entries there are ~43K different values for
this field, withe each category typically having 2-6 sub categories
- category_id_s: not matched in this query, in the DB of ~500K entries
there are ~13K different values for this field
- status_s: has one of 2 values, in the query described baove all hits will
have the value "active"
- user_id_s: unique within the DB but not matched in this query
- first_name_s: almost unique within the DB, this query will sort by this
field
- last_name_s: almost unique within the DB, this query will sort by this
field

This search query looks like:
<<"sub_category_id_s:test_1 AND status_s:active AND type_s:sub_category">>

Our options parameter has the sort directive:
{sort, <<"first_name_s asc, last_name_s asc">>}

The query was run on a 5-node cluster with n_val of 3.

Thanks in advance fo rany pointers!
//Sean.
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