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LucidDB questions

Becker, Bill
Hello,

Some questions regarding LucidDB/Squirrel:
1) Squirrel keeps asking for a Hibernate dialect; this seems to be
   related to syntax, as it displays a list of databases to choose
   from. Which Hibernate dialect should I choose for LucidDB?

2) I looked thru the SYS_ROOT.DBA_VIEWS, but couldn't see anything
   related to which columns are compressed, what type of compression
   is used, degree of compression, etc. Where could I find column
   compression information within LucidDB?

3) Is a complete set of "SET" commands available anywhere?

I have looked thru the online docs. Thanks for making this tool available.


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Re: LucidDB questions

Zelaine Fong-3
Becker, Bill wrote:
>
> 2) I looked thru the SYS_ROOT.DBA_VIEWS, but couldn't see anything
>    related to which columns are compressed, what type of compression
>    is used, degree of compression, etc. Where could I find column
>    compression information within LucidDB?

LucidDB currently does not expose the compression mode used on each
column.  To find out the degree of compression, you'll need to look at
the number of pages occupied by each cluster and compare it against the
number of rows in the table multiplied by the number of bytes for the
datatype of the column.

To see the number of pages occupied by each cluster, run the following
query:

select "name", "pageCount" from sys_fem."MED"."LocalIndex" where "name"
like 'SYS$CLUSTERED%';

You can get the row count by querying on sys_root.dba_stored_tables.

>
> 3) Is a complete set of "SET" commands available anywhere?
>

I currently can't access the online docs, but from the main LucidDB
document page, there's a LucidDbSqlReference link.  On that page, there
are links to the different statements.  Look under "Miscellaneous
Statements".

-- Zelaine



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Re: LucidDB questions

John Sichi
Administrator
In reply to this post by Becker, Bill
Becker, Bill wrote:
> Some questions regarding LucidDB/Squirrel:
> 1) Squirrel keeps asking for a Hibernate dialect; this seems to be
>    related to syntax, as it displays a list of databases to choose
>    from. Which Hibernate dialect should I choose for LucidDB?

I haven't seen this.  I just downloaded the latest Squirrel (2.6.5a) and
it didn't ask about Hibernate dialect.  What actions trigger the dialog?

I did notice that there's now an HQL tab, but I didn't try that (LucidDB
wouldn't be a good match for Hibernate since Hibernate is oriented
towards transactional data access rather than analytical).

LucidDB follows SQL:2003, so in general, if forced to choose a SQL
dialect, pick whatever is close to that.

JVS


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Re: LucidDB questions

John Sichi
Administrator
In reply to this post by Zelaine Fong-3
Zelaine Fong wrote:

> Becker, Bill wrote:
>> 2) I looked thru the SYS_ROOT.DBA_VIEWS, but couldn't see anything
>>    related to which columns are compressed, what type of compression
>>    is used, degree of compression, etc. Where could I find column
>>    compression information within LucidDB?
>
> LucidDB currently does not expose the compression mode used on each
> column.  To find out the degree of compression, you'll need to look at
> the number of pages occupied by each cluster and compare it against the
> number of rows in the table multiplied by the number of bytes for the
> datatype of the column.
>
> To see the number of pages occupied by each cluster, run the following
> query:
>
> select "name", "pageCount" from sys_fem."MED"."LocalIndex" where "name"
> like 'SYS$CLUSTERED%';

The view Zelaine mentions above is internal; I've logged a JIRA issue
for exposing this information as part of the official system views in a
future release:

http://issues.eigenbase.org/browse/LDB-173

Also note that it's necessary to run ANALYZE on the table before
querying the view above, otherwise the page counts won't be populated:

analyze table schema_name.table_name
estimate statistics for all columns;

>> 3) Is a complete set of "SET" commands available anywhere?
>>
>
> I currently can't access the online docs, but from the main LucidDB
> document page, there's a LucidDbSqlReference link.  On that page, there
> are links to the different statements.  Look under "Miscellaneous
> Statements".

Here's the link:

http://pub.eigenbase.org/wiki/LucidDbSqlReference

For ALTER SESSION/SYSTEM SET..., parameters are documented here:

http://pub.eigenbase.org/wiki/LucidDbSystemParameters
http://pub.eigenbase.org/wiki/LucidDbSessionParameters

The !set commands for sqlline aren't part of SQL:

http://sqlline.sourceforge.net/

JVS


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Re: LucidDB questions

John Sichi
Administrator
In reply to this post by Becker, Bill
Becker, Bill wrote:
>  It pops up when you right-click on a table, then select
> refactoring, then column -> modify. I think it will pop up
> when you select any of the refactoring table or column choices.
> My interpretation is that it wants to know which syntax to use
> when creating the Sql command. The dialog displays a list of
> databases (Axion, DB2, SqlServer, Oracle, etc.). I have tried several,
> but the command always seems to fail with a syntax error.
> Thanks for your help.

Oh, I see...it wants to know how to construct ALTER TABLE syntax (which
varies a lot across DBMS's beyond the lowest-common-denominator standard
ADD COLUMN).  Well, as a matter of fact, LucidDB does not yet support
ALTER TABLE, so none of them will work yet :)

We currently have a project under way to ADD COLUMN support.

JVS

> -----Original Message-----
> From: John V. Sichi [mailto:[hidden email]]
> Sent: Thursday, March 20, 2008 9:27 PM
> To: Becker, Bill
> Cc: Luciddb-users (E-mail)
> Subject: Re: [luciddb-users] LucidDB questions
>
>
> Becker, Bill wrote:
>> Some questions regarding LucidDB/Squirrel:
>> 1) Squirrel keeps asking for a Hibernate dialect; this seems to be
>>    related to syntax, as it displays a list of databases to choose
>>    from. Which Hibernate dialect should I choose for LucidDB?
>
> I haven't seen this.  I just downloaded the latest Squirrel (2.6.5a) and
> it didn't ask about Hibernate dialect.  What actions trigger the dialog?
>
> I did notice that there's now an HQL tab, but I didn't try that (LucidDB
> wouldn't be a good match for Hibernate since Hibernate is oriented
> towards transactional data access rather than analytical).
>
> LucidDB follows SQL:2003, so in general, if forced to choose a SQL
> dialect, pick whatever is close to that.
>
> JVS
>



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Re: LucidDB questions

Jeremy Lemaire
Periodically I see this SEVERE error in the Trace.log. It appears to happen at a fixed 20 seconds interval.  

Mar 29, 2010 1:35:06 PM de.simplicit.vjdbc.server.command.CommandProcessor process
SEVERE: Unknown connection entry 23 for command PingCommand

I have closed all client connections, checked for zombies via ps, and even restarted the server to try and clear it out but nothing seems to work. According to the dba_sql_statements table there are no rogue statement being processed either.

What does this mean and how do stop it from filling up my logs?
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Re: LucidDB questions

John Sichi
Administrator
Are you using HTTP or RMI?

I have seen this occasionally, but not periodically the way you are
describing.  I think it is something harmless from VJDBC, but it would
be good to be able to track it down.

JVS

haawker wrote:

> Periodically I see this SEVERE error in the Trace.log. It appears to happen
> at a fixed 20 seconds interval.  
>
> Mar 29, 2010 1:35:06 PM de.simplicit.vjdbc.server.command.CommandProcessor
> process
> SEVERE: Unknown connection entry 23 for command PingCommand
>
> I have closed all client connections, checked for zombies via ps, and even
> restarted the server to try and clear it out but nothing seems to work.
> According to the dba_sql_statements table there are no rogue statement being
> processed either.
>
> What does this mean and how do stop it from filling up my logs?


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Re: LucidDB questions

Jeremy Lemaire
I am using HTTP with version 0.9.2 and I am making JDBC connections via sqllineClient and/or SQuirreL.
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Re: LucidDB questions

John Sichi
Administrator
In reply to this post by Jeremy Lemaire
I left a server running with a connection open, and I was able to
reproduce your problem.  In fact, the connection seems to have been
cleaned up after a timeout on the server side, so that further commands
from it fail with a similar exception.  The ping must be from the client
side.  We had a similar problem in the past with RMI, which is when we
added the connectionTimeoutMillis parameter (default 1 day), but this
must be something different for HTTP.

Thanks for the report; I'll investigate the relevant VJDBC settings.

JVS

haawker wrote:

> Periodically I see this SEVERE error in the Trace.log. It appears to happen
> at a fixed 20 seconds interval.  
>
> Mar 29, 2010 1:35:06 PM de.simplicit.vjdbc.server.command.CommandProcessor
> process
> SEVERE: Unknown connection entry 23 for command PingCommand
>
> I have closed all client connections, checked for zombies via ps, and even
> restarted the server to try and clear it out but nothing seems to work.
> According to the dba_sql_statements table there are no rogue statement being
> processed either.
>
> What does this mean and how do stop it from filling up my logs?


------------------------------------------------------------------------------
Download Intel® Parallel Studio Eval
Try the new software tools for yourself. Speed compiling, find bugs
proactively, and fine-tune applications for parallel performance.
See why Intel Parallel Studio got high marks during beta.
http://p.sf.net/sfu/intel-sw-dev
_______________________________________________
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