When eliminating NULL values with SQL Server queries we typically reach for ISNULL or COALESCE to do the job. Generally speaking they’ll provide equivalent results, but they work in different ways. If you’re dealing with logic more complex than ISNULL(ColA, ColB) – for example using a function or subquery as part of the expression – then you might be in for a surprise. […]
Handling data modifications to large tables can be tricky. We can end up with long running queries and large transactions. Efficiently handling them comes from batching. Effective batching in general helps us by: In this post we’ll take a look at a key-range approach to solve the issue. With this solution a batch will be […]
Performance issues in SSIS packages can be tough to track down. You know something is off but trawling through pages of SSIS reporting and the validation noise is frustrating. Adding your own logging is a nice idea but not feasible at scale. An alternative? Querying internal tables within the SSIS database is a quicker way […]
One particular performance issue with SSIS data flows can fly under the radar – spilling to disk. This isn’t clearly visible through regular debugging or execution so can go unnoticed. And it hurts. Paging to disk is bad for performance. Disks are much slower to access than memory, so we want to keep our data […]
We’ve recently looked at how caching can improve performance and I wanted to show how we can eek even more performance out of caches by using a custom approach I’ll term Selective Caching. I’ll note here that there’s a potential gotcha with this approach which we’ll get to before the end of the post! Scenario Let’s say […]
Last week we looked at using a cache to improve lookup performance. We saw how a cache improves performance by being able to reuse reference data repeatedly. That used a regular cache but it’s not the only option available to us. In this post we’re going to look at the File Cache option which can achieve […]
Lookup transformations provide us a way to access related values from another source, such as retrieving surrogate keys in data warehousing. When we need multiple lookups to the same reference data we can improve performance through the use of a Cache. If we consider data warehousing, a prime example of this would be an order […]
When running queries, reviewing execution plans, or diving into Query Store it’s not uncommon to see missing index recommendations, particularly for more complex queries. But are they any good? There are many factors when considering an index. However if you’re a situation where these missing index recommendations are enticing, I wanted to cover 3 key areas you […]
When using data flows in SSIS packages we want the flow to be fast and fluid. Improving performance of the flows will vary in different packages, but one element can consistently help – tuning memory utilisation. In this post we’ll look at tuning the memory utilisation by altering the number of rows passing through the flow concurrently. […]
When looking to increase performance for a database it can be the smaller and faster queries which can be improved easier and more effectively than their slower counterparts. We can be drawn to tuning long running and complex queries, but these can be a challenge due to their size and complexity. Sometimes though we can reclaim just […]
Andy Brownsword 