Building an Oracle to PostgreSQL migrator: Lessons learned
Moving from Oracle to PostgreSQL has become a popular sport, widely adopted by many who want to free themselves from license costs, hefty support costs and also technical limitations on the Oracle side. The same is true for people moving from MS SQL and other commercial platforms to PostgreSQL. However, my impression is that moving […]
PostgreSQL: Create indexes after bulk loading
Over the years, many of our PostgreSQL clients have asked whether it makes sense to create indexes before – or after – importing data. Does it make sense to disable indexes when bulk loading data, or is it better to keep them enabled? This is an important question for people involved in data warehousing and […]
PostgreSQL: The power of a SINGLE missing index
Index missing? When an index is missing, good performance won’t be kissing a PostgreSQL user looking for efficiency but instead feels like a legacy. To satisfy a DBA’s desire and thirst, let us load some data first. pgbench is the tool of the day but the next listing will explain that anyway: Loading millions of […]
Fixing out-of-sync sequences in PostgreSQL
Creating auto increment columns in PostgreSQL is easy. Simply use two pseudo data types serial and serial8, respectively, then PostgreSQL will automatically take care of your auto increment columns. However, once in a while problems can still occur. Let us take a look and see. Sequences: Avoid manual values To understand the underlying problem, one […]
PostgreSQL grouping sets: ROLLUP & CUBE
PostgreSQL is one of the best OLTP databases (OLTP = online transaction processing) in the world. However, it can do more than just OLTP. PostgreSQL offers many additional features relevant to a more OLAP-style workload. One of those features is called “GROUPING SETS”. Before we dive into the details, I’ve compiled some sample data which […]
PostgreSQL Security: Things to avoid in real life
Hardening PostgreSQL has become ever more important. Security is king these days and people want to know how to make PostgreSQL safe. Some of us might still remember what happened to MongoDB in recent years and we certainly want to avoid similar security problems in the PostgreSQL world. What happened to MongoDB is actually stunning: […]
PostgreSQL zheap: Current status
zheap has been designed as a new storage engine to handle UPDATE in PostgreSQL more efficiently. A lot has happened since my last report on this important topic, and I thought it would make sense to give readers a bit of a status update – to see how things are going, and what the current […]
PostgreSQL: LIMIT vs FETCH FIRST ROWS … WITH TIES
Most people in the SQL and in the PostgreSQL community have used the LIMIT clause provided by many database engines. However, what many do not know is that LIMIT / OFFSET are off standard and are thus not portable. The proper way to handle LIMIT is basically to use SELECT … FETCH FIRST ROWS. However, […]
Understanding LATERAL joins in PostgreSQL
LATERAL joins are one of the lesser-known features of PostgreSQL and other relational databases such as Oracle, DB2 and MS SQL. However, LATERAL joins are a really useful feature, and it makes sense to take a look at what you can accomplish with them. Inspecting FROM more closely Before we dive into LATERAL, it makes […]
PostgreSQL: Constraints over multiple rows
In PostgreSQL and many other relational databases, constraints are an integral part of the feature set. Many people are aware of primary keys, foreign keys, CHECK-constraints, table constraints and so on. However, from time to time, the situation is way more complicated. That’s when some more advanced techniques are needed to enforce integrity in the […]
Creating and refreshing materialized views in PostgreSQL
A “materialized view” is a database object which stores the result of a precalculated database query and makes it easy to refresh this result as needed. Materialized views are an integral feature of pretty much all advanced database systems. Naturally, PostgreSQL also provides support for materialized views, and offers the end-user a powerful tool to […]
Data warehousing: Making use of synchronized seq scans
PostgreSQL contains some hidden gems which have been around for many years and help to silently speed up your queries. They optimize your SQL statements in a clever and totally transparent way. One of those hidden gems is the ability to synchronize sequential scans. Actually, this feature has been around for 15+ years, but has […]