In PostgreSQL, a partial index is an index that’s built on a subset of the rows in a table. It includes only the rows that satisfy a given condition specified with the WHERE clause.
Partial indexes can help us achieve faster queries, reduced storage, and lower overhead for write-heavy workloads.
Below is a quick example that demonstrates how to create a partial index in PostgreSQL.
When a prepared statement is created in PostgreSQL, the server has two possible strategies for executing it: use a generic query plan or use a custom plan. Each time we run a prepared statement it will chose one of these two plans.
By default, it will use a custom plan for the first five runs. After that it will decide whether or not it’s more efficient to use a generic plan for subsequent executions, or stay with a custom plan.
This begs the question; how do we check to see which plan PostgreSQL chose?
Whenever we create a table in PostgreSQL, a composite type is automatically created behind the scenes. This composite type is based on the table that we created. Each column in the table becomes a field in the composite type.
If the table already uses a composite type, then the composite type that PostgreSQL creates will include that type in its definition, thereby creating a situation where we effectively have a nested composite type.
Most relational database management systems support the TRUNCATE statement, and PostgreSQL is no exception.
That said, PostgreSQL has a few differences in the way its TRUNCATE statement works when compared to many other RDBMSs.
In this article, we’ll explore the various features of PostgreSQL’s implementation of the TRUNCATE statement, along with examples to demonstrate.
When we have a column with composite data in PostgreSQL, we can access each field by using dot notation. This is true whether we select the data or update it. This means that we can use dot notation to update individual fields within a composite column.
And if we need to update all fields at once, we can use the ROW constructor.
PostgreSQL provides us with a couple of functions that allow us to pad strings. We can use these functions to put one or more space characters or other characters on either the right side, left side, or both sides of the string.
When working with databases (and software in general), string concatenation is the operation of joining character strings end-to-end. For example if we have two words, we can combine them into one.
PostgreSQL provides us with multiple ways to concatenate strings. Below are two functions and one operator that we can use to concatenate strings in PostgreSQL.
In PostgreSQL, both UNIQUE indexes and UNIQUE constraints can be used to enforce uniqueness on columns.
So you may be wondering; if that’s true, why have both? And are there any circumstances that we should choose one over the other?
Let’s find out.
In PostgreSQL, indexes on expressions (also known as “functional indexes”) allow you to create an index not just on a column but on the result of an expression or function applied to a column (or multiple columns). This can significantly improve query performance when the same expression is used frequently in queries, especially for complex calculations or transformations.