Despite the ongoing tragic events, we continue the series. In the last article we reviewed the stages of query execution . Before we move on to plan node operations (data access and join methods), let's discuss the bread and butter of the cost optimizer: statistics. As usual, I use the demo database for all my examples. You can download it and follow along. You will see a lot of execution plans here today. We will discuss how the plans work in more detail in later articles. For now just pay a...| postgrespro.com
Hello! I'm kicking off another article series about the internals of PostgreSQL. This one will focus on query planning and execution mechanics. This series will cover: query execution stages (this article), statistics, sequential and index scans, nested-loop, hash, and merge joins. Many thanks to Alexander Meleshko for the translation of this series into English. This article borrows from our course QPT Query Optimization (available in English soon), but focuses mostly on the internal mechani...| postgrespro.com
So far we have covered query execution stages , statistics , sequential and index scan , and have moved on to joins. The previous article focused on the nested loop join , and in this one I will explain the hash join . I will also briefly mention group-bys and distincs.| postgrespro.com
So far we've discussed query execution stages , statistics , and the two basic data access methods: Sequential scan and Index scan . The next item on the list is join methods. This article will remind you what logical join types are out there, and then discuss one of three physical join methods, the Nested loop join. Additionally, we will check out the row memoization feature introduced in PostgreSQL 14. Joins Joins are the primary feature of SQL, the foundation that enables its power and agi...| postgrespro.com
In previous articles we discussed query execution stages and statistics . Last time, I started on data access methods, namely Sequential scan . Today we will cover Index Scan. This article requires a basic understanding of the index method interface. If words like "operator class" and "access method properties" don't ring a bell, check out my article on indexes from a while back for a refresher. Plain Index Scan Indexes return row version IDs (tuple IDs, or TIDs for short), which can be handl...| postgrespro.com