![]() ![]() ![]() Unique indexesĪ unique index makes sure that your table does not have more than one row with the same value. To create an index of any other type, you need to specify it – hash, gist, spgist, gin, or brin.īesides the abovementioned index types, we can single out several index subsets. Only the B-Tree index type does not require any additional specification in the CREATE INDEX statement, as it is the default one in PostgreSQL. A block range is a group of pages that are physically adjacent in the table BRIN indexes store summary information-page number along with minimum and maximum values-for each block range. Block Range Index (BRIN)īRIN (Block Range Index) applies to large tables where specific columns have a natural correlation with their physical location in the table. The common characteristic of these structures is that they repeatedly divide the search space into partitions that do not have to be of the same size. The SP-GiST (Space-Partitioned GiST) index is similar to GiST, but it uses a partitioned search tree to index non-balanced data structures, thus simplifying the SEARCH and INSERT operations. It is applicable for full-text search as well. GiST is also useful if you have queries that are not indexable with B-Tree. The GiST (Generalized Search Tree) index allows using the tree structure to index schemes for new data types-for instance, geometric data types and network address data. Note that the GIN index will be slower for INSERT and UPDATE operations. The most common case for applying the GIN index comprises operations with data types such as arrays, range types, JSON, and also for full-text search. ![]() GIN (Generalized Inverted Index) is suitable for mapping multiple values to one row. Hash indexes are rarely used in PostgreSQL because it is necessary to rebuild them manually after crashes, and they can cause issues during transactions. It is called hash because it stores a 32-bit hash code derived from the indexed column value. Hash is a specific index type applied only if the equality condition = is being used in the query. B-Tree is the most common index type, suitable for most cases. It is compatible with all data types, and it can be used, for instance, to retrieve NULL values and work with caching. ![]() These six types are as follows:ī-Tree is the default index type for the CREATE INDEX command in PostgreSQL. They also determine the syntax specifics. There are six types of PostgreSQL indexes, which are also called methods, because they define the way each particular index handles its task.
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