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Re: [PERFORM] Partioning tsearch2 a table into chunks and accessing via views

From: Benjamin Arai <me(at)benjaminarai(dot)com>
To: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
Cc: Brandon Shalton <brandon(at)cydataservices(dot)com>,PostgreSQL <pgsql-general(at)postgresql(dot)org>,pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] Partioning tsearch2 a table into chunks and accessing via views
Date: 2007-08-25 19:49:13
Message-ID: 22B8D5DC-456F-4337-A1D9-B2C9125CA71E@benjaminarai.com (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-performance
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Since I am using tsearch2 on the table I think there is going to be a  
significant performance hit - e.g., I partition by batch (batches are  
not separated by date, they are essentially random subsets of a much  
larger data-set).  I am querying this database using tsearch2, so I  
am assuming all tables are going to be queried each time since the  
text is not partition by any specific constraint - e.g., >R goes to  
table 1 and <=R goes to table 2.

Benjamin

On Aug 25, 2007, at 11:18 AM, Joshua D. Drake wrote:

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> Benjamin Arai wrote:
>> As stated in the previous email if I use partitioning then queries  
>> will
>> be executed sequentially - i.e., instead of log(n) it would be (#
>> partitions) * log(n).  Right?
>
> The planner will consider every relevant partition during the  
> execution.
> Which may be a performance hit, it may not be. It depends on many
> factors. In general however, partitioning when done correctly is a
> performance benefit and a maintenance benefit.
>
> Sincerely,
>
> Joshua D. Drake
>
>
>>
>> Benjamin
>>
>> On Aug 25, 2007, at 9:18 AM, Joshua D. Drake wrote:
>>
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>>> Benjamin Arai wrote:
>>>> This kind of disappointing, I was hoping there was more that  
>>>> could be
>>>> done.
>>>>
>>>> There has to be another way to do incremental indexing without  
>>>> loosing
>>>> that much performance.
>>
>>> What makes you think you are loosing performance by using  
>>> partitioning?
>>
>>> Joshua D. Drake
>>
>>>>
>>>> Benjamin
>>>>
>>>> On Aug 24, 2007, at 6:29 PM, Joshua D. Drake wrote:
>>>>
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>>>>> Brandon Shalton wrote:
>>>>>> Benjamin,
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> In order to avoid the re-indexing I was thinking of instead  
>>>>>>> creating
>>>>>>> a new
>>>>>>> table each month (building its indexes and etc) and accessing  
>>>>>>> them
>>>>>>> all
>>>>>>> through a view. This way I only have to index the new data each
>>>>>>> month.
>>>>>>>
>>>>>>
>>>>>> Take a look at bizgres.org (based on postgres).
>>>>>>
>>>>>> They have a parent-child structure.
>>>>>>
>>>>>> The way i use it, is I have about 30M records a day that are  
>>>>>> inserted
>>>>>> into the database.
>>>>>>
>>>>>> Each day is a "child" table to the "parent".
>>>>>>
>>>>>> so example:
>>>>>>
>>>>>> the parent table is called  "logfile"
>>>>>>
>>>>>> each day, is a child, with the structure like  "logfile_YYMMDD"
>>>>>>
>>>>>> the "child" inherits the table structure of the parent, such  
>>>>>> that you
>>>>>> could query the child table name directly, or you run the query
>>>>>> against
>>>>>> the parent (ie. logfile table) and get all the data.
>>>>>>
>>>>>> the indexes are done on a per table basis, so new data that comes
>>>>>> in, is
>>>>>> a lesser amount, and doesn't require re-indexing.
>>>>
>>>>
>>>>> PostgreSQL can do all of this too.
>>>>
>>>>> Sincerely,
>>>>
>>>>> Joshua D. Drake
>>>>
>>>>>>
>>>>>>
>>>>>> example:
>>>>>>
>>>>>> select * from logfile_070825 where datafield = 'foo'
>>>>>>
>>>>>> if i knew i wanted to specifically go into that child, or:
>>>>>>
>>>>>> select * from logfile where datafield = 'foo'
>>>>>>
>>>>>> and all child tables are searched and results merged.  You can  
>>>>>> perform
>>>>>> any kind of sql query and field structures are you normally do.
>>>>>>
>>>>>> the downside is that the queries are run sequentially.
>>>>>>
>>>>>> so if you had 100 child tables, each table is queried via  
>>>>>> indexes,
>>>>>> then
>>>>>> results are merged.
>>>>>>
>>>>>> but, this approach does allow me to dump alot of data in, without
>>>>>> having
>>>>>> the re-indexing issues you are facing.
>>>>>>
>>>>>> at some point, you could roll up the days, in to weekly child  
>>>>>> tables,
>>>>>> then monthly tables, etc.
>>>>>>
>>>>>> I believe Bizgres has a new version of their system that does  
>>>>>> parallel
>>>>>> queries which would certainly speed things up.
>>>>>>
>>>>>> For your documents, you can do it by the day it was checked  
>>>>>> in, or
>>>>>> maybe
>>>>>> you have some other way of logically grouping, but the parent/ 
>>>>>> child
>>>>>> table structure really helped to solve my problem of adding in
>>>>>> millions
>>>>>> of records each day.
>>>>>>
>>>>>> The closest thing in mysql is using merge tables, which is not  
>>>>>> really
>>>>>> practical when it comes time to do the joins to the tables.
>>>>>>
>>>>>> -brandon
>>>>>>
>>>>>> http://www.t3report.com - marketing intelligence for online  
>>>>>> marketing
>>>>>> and affiliate programs
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> ---------------------------(end of
>>>>>> broadcast)---------------------------
>>>>>> TIP 6: explain analyze is your friend
>>>>>>
>>>>
>>>>
>>>>> - --
>>>>
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>>>>>
>>
>>
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>>> broadcast)---------------------------
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>>
>>
>>
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>>
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>>>
>
>
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