In previous articles we discussed how the system plans a query execution and how it collects statistics to select the best plan. The following articles, starting with this one, will focus on what a plan actually is, what it consists of and how it is executed. In this article, I will demonstrate how the planner calculates execution costs. I will also discuss access methods and how they affect these costs, and use the sequential scan method as an illustration. Lastly, I will talk about parallel...| 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
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
