You can use varchar or text instead, with a CHECK constraint - or (if the id is so uuid-like) the uuid type itself. Note 2: The char(n) type is also discouraged. Note: Unfortunately, oid is not the best name for a column in PostgreSQL, because it can also be a name for a system column and type. For these reasons, hash index use is presently discouraged.Ĭurrently, only the B-tree, GiST and GIN index methods support multicolumn indexes. Also, changes to hash indexes are not replicated over streaming or file-based replication after the initial base backup, so they give wrong answers to queries that subsequently use them. Hash index operations are not presently WAL-logged, so hash indexes might need to be rebuilt with REINDEX after a database crash if there were unwritten changes. CREATE INDEX name ON table USING hash (column) īut, if you are willing to do this, you should be aware that there is some limitation on the hash indexes (up until PostgreSQL 10): You can set up a hash index too, if you want (besides the PRIMARY KEY constraint) - but you cannot make that unique. The PRIMARY KEY constraint is a combination of the UNIQUE and the NOT NULL constraints, so (currently) it only supports B-tree. Note, that only B-tree currently supports unique indexes. Pinal Dave is an SQL Server Performance Tuning Expert and independent consultant with over 17 years of hands-on experience.He holds a Masters of Science degree and numerous database. Most entities in EF have a single key, which maps to the concept of a primary key in relational databases (for entities without keys, see Keyless entities).Entities can have additional keys beyond the primary key (see Alternate Keys for more information). Utility to create a PostgreSQL database schema overview in HTML, DOT and XML postgresql-client (13+225) front-end programs for PostgreSQL (supported version).
a UNIQUE constraint will create a unique index. A key serves as a unique identifier for each entity instance. Some constraints can create index(es) in order to work properly (but this fact should not be relied upon).
I assume, you meant to use the hash index method / type.
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