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From Maryann Xue <maryann....@gmail.com>
Subject Re: Inner Join not returning any results in Phoenix
Date Fri, 20 Feb 2015 17:45:55 GMT
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*
>
>
>
>
>

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