Categories
PeopleTools Performance SQL SQL Server

PeopleTools and Parallelism on SQL Server

During a recent discussion with another PS Admin running on SQL Server it became apparent that his efforts to improve application SQL performance through adding more CPUs (with the associated license costs) were based on a fundamentally wrong assumption:

PeopleTools/Application SQL will go parallel if needed.

This is simply not true. In fact, most SELECT SQL can never go parallel under PeopleTools on SQL server due to the fact that they are run through cursors and PeopleTools requests a cursor type of FAST_FORWARD. FAST_FORWARD cursors result in an execution plan with a NonParallelReason value of NoParallelFastForwardCursor.

Categories
PeopleTools Performance SQL Server Tuning

PeopleTools Indexing on SQL Server

PeopleTools was designed to be database agnostic. In the past, the database support included databases such as Gupta SQLBase, Allbase, Informix and Sybase. The ability to support multiple platforms and add others relatively easily was a consequence of some excellent initial design decisions. Sadly, database platform support has dwindled to Oracle, SQL Server and DB2 in more recent releases of PeopleTools.

However, supporting multiple databases in this way meant that many database specific features were not taken advantage of. Since the Oracle takeover of Peopleoft, there have been msome oves to add some Oracle database specific feature support e.g. GTT, but almost nothing on the other databases.

Categories
PeopleTools SQL Server Tuning Upgrade

PSTREENODE Clustered Index Change

I noticed that in PT 8.55 (well at least in .08 and later) that the PeopleTools meta-data for the Clustered Index on PSTREENODE lost the “clustered” attribute. I’m not sure why this was changed but you should be aware that this change could impact your execution plans – especially if you use row level security.

PT 8.55 loses Clustered Flag on "key"
PT 8.55 loses Clustered Flag on “key”

 

"Key" is now Nonclustered
“Key” is now Nonclustered

 

And, more importantly what we now have is a “heap” and so data is no longer ordered as we might expect. This also forces any sequential access to refer to index allocation map pages. Overall, changing this is not something to be done lightly, and I do wonder at the thought process behind this change – or was it just a mistake?

Categories
Hints and Tips SQL SQL Server

CROSS/OUTER APPLY and Performance

One quite useful technique to be aware of is the use of CROSS or OUTER APPLY with an in-line SQL e.g.

 

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INSERT INTO {TABLE}
 
SELECT A.{FIELDS},APP.{FIELDS}
 
FROM {TableA} A CROSS/OUTER APPLY (
 
SELECT {more FIELDS} FROM {TableB} B WHERE .. A.{some_field} = B.{some_field}
 
) APP

However, with CROSS APPLY, the SQL Server optimizer tends to change the logic into regular joins. Mostly this is a good thing, but not if you want to “force” the driving table to be {TableA}. This can offer a considerable performance boost in some circumstances.

What you can do to force this behaviour is to add TOP 1 to the inner SELECT – assuming you expect only one row back from the CROSS APPLY SQL. Or you ordered the SQL result set and *do* just want the first row e.g. maximum/minimum effective date.

Note: CROSS/OUTER APPLY are SQL Server specific syntax for LATERAL in Oracle and others.

Categories
Elasticsearch Kibana SQL Server

Reducing SQL Server logspace usage

Further to my post on using Elasticsearch and Kibana to visualize SQL Server logspace usage, it turned out that this data allowed me to suggest an alternative scheduling time for a large update job (to span a log backup point).

As a result of this we should be able to reduce peak logspace usage from 25% of allocated space to around 20% – thus allowing the log file to be reduced in size dramatically.

Categories
Hints and Tips One-liners Perl SQL Server Windows

Opening UTF-16LE files in Perl

Placeholder for useful code snippet:

open my $fh, '<:raw:perlio:encoding(UTF-16LE):crlf', $filename

which will convert CR/LF combinations to LF only. Alternatively, to keep them intact:

open my $fh, '<:raw:perlio:encoding(UTF-16LE)', $filename

Useful for reading Windows registry export files, SQL server log export files etc.

Categories
Elasticsearch ELK Kibana Peoplesoft Perl SQL Server

Visualizing SQL Server Logspace Usage with Elasticsearch, Kibana and Perl

There are many ways possible ways to collect logspace usage data from SQL Server – this was a quick way using the tools I had at hand – DBCC, perl, elastic search and kibana.

All I did was capture the output of:

DBCC SQLPERF(logspace)

into a temporary table using a simple perl script using DBI. I then did a SELECT against the temporary table in the same perl script and posted the resulting data into ES using the Search::Elasticsearch CPAN module. The ES index was very simple – just 4 columns: database, logspace, logspaceused (%) and the timestamp of the capture (GETDATE()).

After that, all I had to do was visualize the data using Kibana. Here’s some sample output:

 

logspaceused graph
Logspace (%) usage over time

A great way to see the log space pressure points which can easily be tied back to specific batch processes at those times.

Categories
Hints and Tips Peoplesoft PeopleTools SQL Server Tuning

PeopleSoft – INCLUDE and WHERE (filtering) on SQL Server Indexes

It is trivial to add support for INCLUDE() and WHERE() clauses on SQL Server indexes in PeopleSoft – just change the model DDL for Index creation to have the two optional clauses defaulted to blank and then override on the specific index as needed:

model_ddl_index_sql_server

Obviously, at the individual index level you will need the full syntax including the keywords e.g.

INCLUDE (col1,col2,col3 …)

WHERE (criteria)

Be aware that the criteria you can include is limited – refer to the Microsoft documentation for more details.

Categories
Performance SQL Server Trace Flags Tuning

SQL 2014 Cardinality Estimator Trace Flags

For reference:

  • 9481  – Use when running SQL Server 2014 with the default database compatibility level 120. Trace flag 9481 forces the query optimizer to use version 70 (the SQL Server 7.0 through SQL Server 2012) of the cardinality estimator when creating the query plan.
  • 2312 – Use when running SQL Server 2014 with database compatibility level 110, which is the compatibility level for SQL Server 2012. Trace flag 2312 forces the query optimizer to use version 120 (the SQL Server 2014 and later) of the cardinality estimator when creating the query plan.
Categories
Hints and Tips SQL SQL Server

Another SQL Tip – A “DATES” Table

A common requirement is to generate a list of the dates between two dates e.g. on a source row we have a FROM and TO date but we need to expand that into a row for each date. One way to do that on SQL Server is via a CTE:
 

---
--- A generated list of dates from 01-01-2013 until 25-01-2054
--- This would be a useful utility view/table in any PS system
--- Table is preferred - CLUSTERED INDEX ON PROCESS_DT provides
--- Important statistics on distribution AND allows for a CLUSTERED INDEX SEEK
--- in execution plan.
---
 
WITH [PROCESS_DATES] AS (
 
SELECT TOP 15000 CAST(DATEADD(DAY,ROW_NUMBER() OVER ( ORDER BY RECNAME),CONVERT(DATE, '2012-12-31')) AS DATE) AS PROCESS_DT,
DATEPART(weekday,DATEADD(DAY,ROW_NUMBER() OVER ( ORDER BY RECNAME),CONVERT(DATE, '2012-12-31'))) AS PROCESS_DT_WEEKDAY
FROM PSRECFIELDDB --- ANY TABLE WITH A NUMBER OF ROWS >= THE TOP VALUE ABOVE WILL DO
 
)

That works fine, but as the comments above indicate, if you are going to do this it is better to generate the list of values into an table, Apart from anything else, why incur the CPU time recalculating this list every time it is accessed – better as a one-off table populate. Note the use of a table known to have more that 15000 rows – this could be any table – even sys.all_objects provided it has enough rows. But if you are generating rows as a one-off you could cartesian (star join) tables to themselves to get enough rows. The 15000 is arbitrary – you could go further ahead.