How To Dev

Introduction The IN clause is usually used in two main cases: Literal Values : When you already know the exact values to filter and the number of elements is small (from a few elements to a few dozen elements). Note that when parsing, Postgres will treat each item in Literal Values as a single node to execute the Parse Tree, so if the number of items is too large, it will consume a lot of RAM and CPU to process By the time planning is executed, the Query Planner will have to traverse this Tree to process, so you should be careful not to query with too many Literal Values as it will significantly affect performance It can be rewritten with EXISTS but it will make the query more complex, so if using Literal Values , it is best to use IN to keep the query simple and easy to understand An example of usage is filtering out orders with statuses like processing or completed . Dynamic List : When the filter list depends on the data of another table. In most cases, it can be replaced by usin...

Introduction A Composite Index is an index type that contains two or more columns on the same table. It includes the following characteristics A Composite Index can be created for a maximum of 32 columns This is the default configuration according to the INDEX_MAX_KEYS constant of Postgres In practice, you should not create an index with more than 3 to 4 columns because it increases the index size, slowing down INSERT/UPDATE/DELETE operations The column order is sorted ascendingly by default However, unlike a standard index where you can sort ascending or descending at will, when using a Composite Index, you can only sort the columns all ascending, all descending or in the exact order specified at creation time For example, when using ON table (c1, c2) (default is all ascending), then You can query ORDER BY c1 ASC, c2 ASC You can query ORDER BY c1 DESC, c2 DESC But the index will not work with the query ORDER BY c1 ASC, c2 DESC Operation Order When using a Composite Index, you must ...