phoenix-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Matthew Johnson <matt.john...@algomi.com>
Subject RE: Inner Join not returning any results in Phoenix
Date Tue, 24 Feb 2015 11:07:29 GMT
Hi Maryann,



Thanks for that - I will schedule an update to the latest version of
Phoenix then for later this week (and try out the merge-join hints).



In the meantime, here are my explain plans:



*JOIN WITH NO SQUIRREL LIMIT*



*PLAN*

*CLIENT 2-CHUNK PARALLEL 1-WAY FULL SCAN OVER mytable1*

*    PARALLEL INNER-JOIN TABLE 0*

*        CLIENT 3-CHUNK PARALLEL 1-WAY FULL SCAN OVER mytable2*



*JOIN WITH SQUIRREL LIMIT 100*



*PLAN*

*CLIENT 2-CHUNK PARALLEL 1-WAY FULL SCAN OVER mytable1*

*CLIENT 100 ROW LIMIT*

*    PARALLEL INNER-JOIN TABLE 0*

*        CLIENT 3-CHUNK SERIAL 1-WAY FULL SCAN OVER mytable2*

*            SERVER FILTER BY PageFilter 100*

*            SERVER 100 ROW LIMIT*

*        CLIENT 100 ROW LIMIT*





I’m not really sure how to read that, but it does seem to suggest that
‘mytable2’ is being limited to 100 – thoughts?



Cheers,

Matt



*From:* Maryann Xue [mailto:maryann.xue@gmail.com]
*Sent:* 23 February 2015 18:10
*To:* user@phoenix.apache.org
*Subject:* Re: Inner Join not returning any results in Phoenix



Hi Matt,



Yes, the upgrade is as easy as that. I believe things will work fine with
existing tables.

I tried with a similar query but didn't see that it was a Phoenix bug. So
could you please try the following explain statement and see the execution
plan:



EXPLAIN *SELECT * FROM "mytable1" hc*

*INNER JOIN “mytable2” bs*

*On hc."myId" = bs.”myId”*





Thanks,

Maryann





On Fri, Feb 20, 2015 at 1:09 PM, Matthew Johnson <matt.johnson@algomi.com>
wrote:

Hi Maryann,



That’s a good point – I am using 4.2.2, so if that feature is 4.3+ then
that would explain why it’s not working. Is upgrading versions of Phoenix
as simple as removing the previous jar from HBase lib folder and dropping
the new Phoenix jar in (and restarting HBase)? Will all the existing
Phoenix tables and views be backwards-compatible and work with the new
version?



Cheers,

Matt





*From:* Maryann Xue [mailto:maryann.xue@gmail.com]
*Sent:* 20 February 2015 17:46


*To:* user@phoenix.apache.org
*Subject:* Re: Inner Join not returning any results in Phoenix



Which version of Phoenix are you using, Matt? This feature is only
available in the latest releases of 4.3/3.3.



On Fri, Feb 20, 2015 at 12:11 PM, Matthew Johnson <matt.johnson@algomi.com>
wrote:

Hi Maryann,



Unfortunately my two tables are roughly the same size (~500k), but I have
tested a different join where one table is ~500k and the other is ~20k and
putting the larger one first is definitely far more performant. I believe
you are right about running out of memory, I can see this repeated a few
times in the region server logs followed by what appears to be a restart or
disconnect:



*[JvmPauseMonitor] util.JvmPauseMonitor: Detected pause in JVM or host
machine (eg GC): pause of approximately 1083ms*



I have been looking at the Phoenix page on joins (
http://phoenix.apache.org/joins.html) and it mentions using Sort-Merge
joins for large tables by using a hint. I have tried this though with no
success:



*SELECT /*+ USE_SORT_MERGE_JOIN*/ count(*) FROM “mytable1” hc*

*INNER JOIN “mytable2” bs*

*On hc.”myId” = bs.”myId”*



Am I putting the hint in the wrong place? Does it need to go next to the
JOIN rather than the SELECT?



I will try increasing the memory available to the Region Servers as well to
see if that helps.



Thanks!

Matt





*From:* Maryann Xue [mailto:maryann.xue@gmail.com]
*Sent:* 20 February 2015 16:28
*To:* user@phoenix.apache.org


*Subject:* Re: Inner Join not returning any results in Phoenix



Hi Matt,



The error you got with "Limit Rows" off might be related to insufficient
memory on region servers for one of your tables. Which is the larger table
between table1 and table2? You might want to try putting the larger table
as the first table in your join query and see if it works.



And I will quickly check if the LIMIT problem is a Phoenix bug and will
keep you posted.





Thanks,

Maryann





On Fri, Feb 20, 2015 at 11:14 AM, Matthew Johnson <matt.johnson@algomi.com>
wrote:

Hi Abe,



Glad to hear I’m not alone! Will try and figure out exactly what’s
happening and maybe raise a Jira :-)





@Constantin – I have tried with and without the “Limit Rows” – but without
it, and without any indexes, the query runs for a while (about 10 minutes?)
and then throws an error:



*Error: Encountered exception in sub plan [0] execution.*



Which I’m guessing is either HBase or Zookeeper timeout. The weird thing is
that in standard SQL databases (eg Oracle, MySQL etc) then the “Limit Rows”
does not affect any aggregate functions like ‘count’, because the actual
number of result rows for a count is just 1 row (the count itself). But in
HBase it seems that the Row Limit, as Abe mentioned, is applied to one of
the table BEFORE it does the join, so it affects the results of the ‘count’
function.



When I try to create my indexes so I am able to do the join without Row
Limit, I get the following error:



ERROR 1029 (42Y88): Mutable secondary indexes must have the
hbase.regionserver.wal.codec property set to
org.apache.hadoop.hbase.regionserver.wal.IndexedWALEditCodec in the
hbase-sites.xml of every region server



Which I am happy to do (will have to wait until outside of business hours
though), but I am curious, will this have any impact on the rest of my
cluster and could it have any unforeseen consequences?



Thanks again for the input!



Cheers,

Matt





*From:* Ciureanu, Constantin (GfK) [mailto:Constantin.Ciureanu@gfk.com]
*Sent:* 20 February 2015 15:48


*To:* user@phoenix.apache.org
*Subject:* RE: Inner Join not returning any results in Phoenix



Hello Matt,



http://codingclues.eu/2008/the-squirrel-100-rows-problem/



Can you please test again after unchecking “Contents- Limit rows” and “SQL
– Limit rows”?



[image: SQL tab]



P.S. Off-topic – it’s as funny as this “problem” (not possible to send an
email for more than 500 miles away J
http://www.ibiblio.org/harris/500milemail.html )



Regards,

  Constantin



*From:* Abe Weinograd [mailto:abe@flonet.com <abe@flonet.com>]
*Sent:* Friday, February 20, 2015 4:18 PM
*To:* user
*Subject:* Re: Inner Join not returning any results in Phoenix



Matt,



I have seen this same issue.  When passing a LIMIT to a query with joins
(most query tools do it implicitly), Phoenix seems to apply that to the
table on the right of the join I believe.  I hadn't had a chance to play
with it more and file a JIRA, but what you are describing is consistent
with what I have seen.



Abe



On Fri, Feb 20, 2015 at 10:04 AM, Matthew Johnson <matt.johnson@algomi.com>
wrote:

Hi Constantin,



Many thanks for your reply – the quotes were both of the same type (double
quotes for table and column names, single quotes for string literals), it
is just my email client that formatted them weirdly, sorry!



I have discovered what I believe is an important piece of the puzzle to my
problem. I am using Squirrel SQL as my JDBC client for Phoenix, and it has
a “Limit Rows” feature. When I try and count the number of rows in a single
table:



*select count(*) from “mytable1”*



I get the expected number of results (eg 20,000). But when I join two
tables together, it seems that the “Limit Rows” from Squirrel is somehow
being applied before the join is performed, and if “Limit Rows” is set to
100 I get 100 results or less. If the inner join is quite sparse (eg 20,000
rows in a table but only 100 of these will join with a second table) then I
believe it tries to join the first 100 it finds and returns no results. In
my experience of Oracle or MySQL, joins are done entirely on server side
and then you just get back the number of rows you limited, rather than what
appears to be happening which is the row limit is applied to the first
table before the join is attempted with the second table. Is that how
Phoenix works?



I have also discovered that I get different results (with “Limit Rows”
turned on) depending on which order I join the tables:



*SELECT count(*) FROM “mytable1” hc*

*INNER JOIN “mytable2” bs*

*On hc.”myId” = bs.”myId”*



Gives me a very different number of results than:



*SELECT count(*) FROM “mytable2” bs*

*INNER JOIN “mytable1” hc*

*On hc.”myId” = bs.”myId”*





Unfortunately I cannot test whether I get the same number of results with
“Limit Rows” turned off because my query times out! So I am now looking at
creating secondary indexes on the “myId” column in both tables to see if I
am able to do this join quicker. Does a join like this use a lot of memory
on server side? Is something likely to be running out of resources?



Many thanks again for your time.



Cheers,

Matt





*From:* Ciureanu, Constantin (GfK) [mailto:Constantin.Ciureanu@gfk.com]
*Sent:* 20 February 2015 14:40
*To:* user@phoenix.apache.org
*Subject:* RE: Inner Join not returning any results in Phoenix



Hi Matthew,



Is it working without the quotes “ / *"*  ?   (I see you are using 2 types
of quotes, weird)

I guess that’s not needed, and probably causing troubles.   I don’t have to
use quotes anyway.



Alternatively check the types of data in those 2 tables (if the field types
are not the same in both tables, the join will not work).



Good luck,

  Constantin



*From:* Matthew Johnson [mailto:matt.johnson@algomi.com
<matt.johnson@algomi.com>]
*Sent:* Friday, February 20, 2015 12:54 PM
*To:* user@phoenix.apache.org
*Subject:* Inner Join not returning any results in Phoenix



Hi guys,



I’m a little bit stuck with doing an Inner Join with Phoenix. I set up one
environment, created tables in HBase, and then created views (rather than
tables) in Phoenix, and am able to query as expected (when I join my two
tables I see results). I’ve just promoted to another environment, with the
exact same setup, but my Inner Join returns no results!



I run the following two individual queries:



*SELECT * FROM "mytable1" hc*

*where hc."myId" = 'XS0'*



*SELECT * FROM "mytable2" bs*

*where bs."myId" = 'XS0'*



And both of these queries give results. But when I run:



*SELECT * FROM "mytable1" hc*

*INNER JOIN “mytable2” bs*

*On hc."myId" = bs.”myId”*



I get no results. I also get no results if I try:



*SELECT * FROM "mytable1" hc*

*where hc."myId" in (select distinct “myId” from “mytable2”)*



I have checked in HBase shell and can see the “myId” value is as expected
(XS0 in both tables). I am not sure if there are any logs that I can look
at to get some insight?



Many thanks in advance for any suggestions!



Cheers,

Matt



*PS* Something that may or may not be of note: In the environments I am
using:

WORKING: *hbase-0.98.8-hadoop2 / phoenix-4.2.2-server.jar*

FAILING:     *hbase-0.98.9-hadoop2* / *phoenix-4.2.2-server.jar*

Mime
View raw message