You may want to look at the query plan between the 3 scenarios to see which
operators time is spend on and how well they are parallelized.
The expectation would be that Parquet will perform better than JSON.
--Andries
> On Mar 7, 2016, at 3:02 PM, Eric Pederson <eric...@gmail.com> wrote:
>
> We are using MapR M3 and are querying multiple JSON files - around 250
> files at 1.5 GB per file. We have a small cluster of three machines
> running Drill 1.4. The JSON is nested three-four levels deep, in a format
> like:
> {
> { "group1":
> { "field1": 42,
> "field2: [ "a", "b", "c" ],
> ...
> }
> { "group2":
> ....
> }
> ...
> }
>
> There are about 500 objects like this in each JSON file.
>
> I've been testing a set of queries that scan all of the data (we're
> investigating a partitioning strategy but haven't settled on one that will
> fit all of our queries which are fairly ad-hoc). These full-scan queries
> typically take 1 minute, 20 seconds using the default settings If I limit
> the query to a single file the query takes a few seconds.
>
> I wanted to see how the number of Drillbits would impact the query time, to
> try to extrapolate to the number of servers needed to reach a performance
> number. Here are the numbers that we saw:
> - 1 Drillbit: 3:45
> - 2 Drillbits: 1:56
> - 3 Drillbits: 1:20
>
> The performance flattens out between two and three Drillbits. I was
> surprised to see that, given the single file query performance. I was
> hoping to throw hardware at the performance a bit more. Is that
> surprising to you?
>
> A somewhat related question. Does Drill take advantage of HDFS locality?
> That is, will it send certain fragments to certain boxes because it knows
> those boxes have the data replicated locally? Actually in our setup (3
> servers) that might be a moot point assuming every box has all blocks. I'm
> not sure if MapRFS changes that.
>
> I also tried converting the JSON files to Parquet using CTAS. The Parquet
> queries took much longer than the JSON queries. Is that expected as well?
>
> Thanks,
>
>
>
> --
> Sent from Gmail Mobile
