Automatic Clustering, Materialized Views and Automatic Maintenance in Snowflake 

Boy are things going bananas at Snowflake these days. The really big news a few weeks back was another round of funding! This week we announced two new major features.

Column And Table Redefinition With Minimal Locking

TLDR: Note to future self… (1) Read this before you modify a table on a live PostgreSQL database. If you do it wrong then your app might totally hang. There is a right way to do it which avoids that. (2) Especially remember the lock_timeout step. Many blog posts around the ‘net are missing this and it’s very important.

Yesterday I was talking to some PostgreSQL users (who, BTW, were doing rather large-scale cool stuff (more...)

Lazy Loading Menu

I've been using the lazy loading concept demonstrated in Maxime's post quite a lot recently, I'd love to see this as a declarative feature one day.

I also wondered if I could apply this concept to the badge count in the side menu.


Turns out it wasn't that hard, particularly since I already had the jQuery I needed from a previous requirement.

We first need to add a unique class to the link definition, so (more...)

Using colplot to visualise performance data

Back in 2011 I wrote a blog post about colplot but at that time focused on running the plot engine backed by a web server. However some people might not want to take this approach, and thinking about security it might not be the best idea in the world anyway. A port that isn’t opened can’t be scanned for vulnerabilities…

So what is colplot anyway? And why this follow-up to a 7 year old post?

Some (more...)

Tuning Time


"“You see,” he continued, beginning to feel better, “once there was no time at all, and people found it very inconvenient.
They never knew whether they were eating lunch or dinner, and they were always missing trains. So time was invented to
help them keep track of the day and get places when they should. When they began to count all the time that was available,
what with 60 seconds in a minute and 60  (more...)

Oracle wait event ‘TCP Socket (KGAS)’

I was asked some time ago what the Oracle database event ‘TCP socket (KGAS)’ means. This blogpost is a deep dive into what this event times in Oracle database 12.1.0.2.180717.

This event is not normally seen, only when TCP connections are initiated from the database using packages like UTL_TCP, UTL_SMTP and the one used in this article, UTL_HTTP.

A very basic explanation is this event times the time that a database (more...)

ADF Task Flow Performance Boost with JET UI Shell Wrapper

ADF application with UI Shell and ADF Task Flows rendered in dynamic tabs would not offer instant switch from one tab to another experience. Thats because tab switch request goes to the server and only when browser gets response - tab switch happens. There is more to this - even if tab in ADF is not currently active (tab is disclosed), tab content (e.g. region rendered from ADF Task Flow) still may participate in (more...)

using AWR on Exadata

Oracle released a brand new Whitepaper for Exadata

How to use AWR Report on Exadata Machines

This Whitepaper gives details how the AWR reports can be used in conjunction with Exadata to monitor and analyze database performance issues

http://www.oracle.com/technetwork/database/availability/exadata-maa-best-practices-155385.html

 

 

 

SparkMeasure, a tool for performance troubleshooting of Apache Spark workloads

SparkMeasure 

 SparkMeasure simplifies the collection and analysis of Spark task metrics data. It is also intended as a working example of how to use Spark listeners for collecting and processing Spark performance metrics.
The work on sparkMeasure has been previously presented in this blog with examples. Recently, an updated version of sparkMeasure (version 0.13) introduces additional integration for the PySpark and Jupyter environments, improved documentation and additional features provided by the community via (more...)

All about headroom and mandatory patching before June 2019

This post was triggered upon rereading a blogpost by Mike Dietrich called databases need patched minimum april 2019. Mike’s blogpost makes it clear this is about databases that are connected using database links, and that:
– Newer databases do not need additional patching for this issue (11.2.0.4, 12.1.0.2, 12.2 and newer).
– Recent PSU patches contain a fix for certain older versions (11.1.0.7, 11.2. (more...)

ADF Postback Payload Size Optimization

Recently I came across property called oracle.adf.view.rich.POSTBACK_PAYLOAD_TYPE. This property helps to optimize postback payload size. It is described in ADF Faces configuration section - A.2.3.16 Postback Payload Size Optimization. ADF partial request is executing HTTP post with values from all fields included. When postback property is set to dirty, it will include into HTTP post only changed values. As result - server will get only changed attributes, (more...)

Introducing SQLdb360: merging eDB360 and SQLd360, while rising the bar to community engagement

Today, we are very happy to release SQLdb360, a new tool that merges together eDB360 and SQLd360, under a single package.

Tools eDB360 and SQLd360 can still be used independently, but now there is only one package to download and keep updated. All the new features and updates to both tools are now in that one package.

The biggest change that comes with SQLdb360 is the kind invitation to everyone interested to contribute (more...)

This Week in PostgreSQL – May 31

Since last October I’ve been periodically writing up summaries of interesting content I see on the internet related to PostgreSQL (generally blog posts). My original motivation was just to learn more about PostgreSQL – but I’ve started sharing them with a few colleagues and received positive feedback.  Thought I’d try posting one of these digests here on the Ardent blog – who knows, maybe a few old readers will find it interesting? Here’s the (more...)

Long-running delete of synopses during table stats gathering

Oracle 11.2.0.4

I recently encountered one long-running session and several blocked sessions, all performing the same delete operation.

--SQL_ID dsf21kcbjqfyk
DELETE FROM SYS.WRI$_OPTSTAT_SYNOPSIS$ WHERE BO# = :B2 AND INTCOL# = :B1;

One session had been running for several hours, and the other sessions were all blocked by a row lock from the first session. Unfortunately, each of these sessions was trying to gather stats on new partitions of tables as part (more...)

SJK is learning new tricks

SJK or (Swiss Java Knife) was my secret weapon for firefighting various types of performance problems for long time.

A new version of SJK was released not too long ago and it contains а bunch of new and powerful features I would like to highlight.

ttop contention monitoring

SJK is living it's name by bundling a number of tool into single executable jar. Though, ttop is a likely single most commonly used tool under SJK (more...)

Oracle ADF BC REST – Performance Review and Tuning

I thought to check how well ADF BC REST scales and how fast it performs. For that reason, I implemented sample ADF BC REST application and executed JMeter stress load test against it. You can access source code for application and JMeter script on my GitHub repository. Application is called Blog Visitor Counter app for a reason - I'm using same app to count blog visitors. This means each time you are accessing blog page (more...)

A look into oracle redo, part 11: log writer worker processes

Starting from Oracle 12, in a default configured database, there are more log writer processes than the well known ‘LGWR’ process itself, which are the ‘LGnn’ processes:

$ ps -ef | grep test | grep lg
oracle   18048     1  0 12:50 ?        00:00:13 ora_lgwr_test
oracle   18052     1  0 12:50 ?        00:00:06 ora_lg00_test
oracle   18056     1  0 12:50 ?        00:00:00 ora_lg01_test

These are the log writer worker processes, for which the minimal amount is equal to the amount public (more...)

FillFactor for UPDATE

What is FillFactor in PostgreSQL?

As per offical Doc —

fillfactor (integer)

The fillfactor for a table is a percentage between 10 and 100. 100 (complete packing) is the default. When a smaller fillfactor is specified, INSERT operations pack table pages only to the indicated percentage; the remaining space on each page is reserved for updating rows on that page. This gives UPDATE a chance to place the updated copy of a row on the (more...)

Oracle to Postgres — Index Skip Scan

I have been working on Oracle to Postgres migration and it has been a fun ride.

One of the recent encounters during migration was performance issue in Postgres for a query, actually quite a simple query.

SELECT count(*) AS num_incidents FROM audit_cs acs INNER JOIN audit_changes ac ON acs.audit_change_id = ac.audit_change_set WHERE acs.object_id=$1 AND ac.path = 'Flag' AND ac.new_value = 'sign' 

Let’s look at the execution plan in Postgres

+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 (more...)

No Asynchronous I/O When Using Shared Server (Also Known As MTS)

I've recently had a case at a client where it was questioned why a particular application was seemingly not making full use of the available I/O capabilities - in comparison to other databases / applications using similar storage.

Basically it ended up in a kind of finger pointing between the application vendor and the IT DBA / storage admins, one side saying that the infrastructure used offers insufficient I/O capabilities (since the most important application (more...)