In this section, we are going to understand the working of PostgreSQL indexes more efficiently, why we need to use the indexes, features of PostgreSQL indexes, a different type of Indexes, and various commands which are performed under the PostgreSQL Indexes section.
What are PostgreSQL Indexes?
In PostgreSQL, Indexes is the special tool used to enhance the retrieval of data from the databases.
A database index is parallel to the index of a book. An index creates an access for all the values, which displays on the indexed columns.
The indexes tend to help the database server to identify the defined rows much faster than it could do without indexes. We have to use the Indexes properly to get the significant result.
Features of PostgreSQL indexes
Some of the essential features of the PostgreSQL indexes are as follows:
- An index is used to enhance the data output with SELECT and WHERE
- If we are using the INSERT and UPDATE commands, it slows down data input.
- Without affecting any of the data, we can CREATE and DROP the
- We can generate an index with the CREATE INDEXcommand’s help by defining the index name and table or column name on which the index is created.
- We can also create a unique index, which is similar to the UNIQUE constraint.
Commands performed under the PostgreSQL Indexes:
In PostgreSQL indexes, we can perform the following commands:
- Create Index
- Drop Index
- List indexes
- Unique Index
- Index on Expression
- Partial index
- Re-index
- Multicolumn Indexes
Let us understand them one by one:
| Commands | Description |
|---|---|
| Create Index | It is used to create a new index by defining the index name and table or column name on which the index is created. |
| Drop Index | The Drop index command is used to delete the current index. |
| List indexes | It is used to represent how to list all indexes in the PostgreSQL database. |
| Unique Index | The Unique index command allows us to specify the unique indexes step by step. |
| Index on Expression | It is used to specify an index based on expressions. |
| Partial index | The partial index is used to display the use of partial indexes. |
| Re-index | To rebuild one or more indices, we can use the REINDEX command. |
| Multicolumn Indexes | It is used to display multicolumn indexes usage to enhance the queries with several conditions in the WHERE clause. |
Types of PostgreSQL Indexes
All the index type uses various algorithm and storage structure to manage different types of commands.
In PostgreSQL, the indexes can be categorized into various parts, which are as follows:
- Hash Indexes
- B-tree Indexes
- GIN Indexes
- GiST Indexes
- SP-GiST indexes
- BRIN Indexes
Hash indexes
When an indexed column is included in the table and compared to the equal (=) operator, the Hash indexes can cope only with simple equality comparison (=) operator.
For this type of scenario, the developer will consider a hash index.
We can use the CREATE INDEX command with the HASH index within the USING clause to create a hash index, as we can see the following illustration:
CREATE INDEX index_name
ON table_name
USING HASH (indexed_column);B-tree indexes
The most important used indexes in PostgreSQL is B-tree indexes.
The B-Tree index is a balance tree, which keeps the sorted data and permits the insertions, searches, deletions, and sequential access in logarithmic time.
The PostgreSQL developer will consider using a B-tree index when index columns are included in an assessment, which uses one of the below operators list:
<
<=
=
>=
BETWEEN
IN
IS NULL
IS NOT NULLFurthermore, for the pattern matching operator LIKE and ~ commands, the query developer can use a B-tree index.
And if the pattern is persistent and is an anchor at the start of the pattern, as we can see in the following example:
column_name LIKE 'abb%'
column_name ~ '^abb'
column_name LKE 'abc%'- Additionally, for ILIKE and ~*,if the pattern begins with a non-alphabetic character, which are not affected by upper/lower case conversion, then the PostgreSQL developer will deliberately use the B-tree indexes.
- The B-tree is a very good option if we have started using an index to optimize our PostgreSQL database.
- If we use the CREATE INDEXcommand without describing any index type, then PostgreSQL uses the B-tree index type by default as it is the best suitable and the most common queries.
GIN indexes
- The next type of PostgreSQL indexes is GIN, which stands for Generalized Inverted Indexes, and it is usually denoted as GIN.
- If we have several values stored in a single column such as range type, array, jsonb, and hstore, the GIN indexes are most beneficial.
GiST Indexes
- The GiST indexes are most commonly used for indexing in full-text search and geometric data types.
- The Generalized Search Tree denotes GiST indexes, which provides a building of general tree structures.
SP-GiST indexes
- The Space-Partitioned GiST is denoted as SP- GiST that keeps up partitioned search trees, which enable the development of an extensive range of dissimilar non-balanced data structures.
- The data which contains a natural clustering element is also not an equally balanced tree, like, multimedia, GIS, IP routing, phone routing, and IP routing, in such cases, we can use the SP-GiST
BRIN
- The BRIN indexes can be maintained easily as it is less costly and much smaller as compared to the B-tree index, and it stands for Block Range Indexes.
- Regularly, the BRIN indexes are used on a column, which contains a linear sort order, such as the generated date column of the sales order
- In PostgreSQL indexes, the BRIN allows the use of an index on a huge table, which would earlier be unusable with B-tree without parallel partitioning.
Disadvantages of using the PostgreSQL Indexes
We have the following reasons for avoiding the PostgreSQL Indexes:
- The PostgreSQL Indexes should not be used on columns, which include a large number of NULL values.
- The PostgreSQL indexes cannot be used with the small tables.
- We do not create indexes for columns, which are often deployed.
- We do not create indexes for tables, with frequent, large batch update or insert operations.
Overview
In the PostgreSQL indexes section, we have learned the following topics:
- The PostgreSQL indexes are used to enhance the retrieval of data from the databases.
- We have understood the features of PostgreSQL indexes.
- We also learned that the PostgreSQL indexes support various commands such as Create Index, Drop Index, List indexes, Unique Index, Index on Expression, Partial index, Re-index, Multicolumn Indexes.
- We have also learned the multiple types of PostgreSQL index, including the HASH indexes, B-tree indexes, GIN Indexes, BRIN indexes, GiST indexes, and SP-GiST indexes.
- And we also learned the disadvantage of using the PostgreSQL Indexes.
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