Questions about indexes
Hi everyone !
I have some little questions about indexes :
Does PostgreSQL create an index when a table is created?
Does it create index even if there is no PK for this table?
If yes, why?
I know that indexes increase performance for SELECT but it is the
contrary when INSERT because the index must be actualised every time,
isn't it?
How can I see all the index that PostgreSQL have implicitly create?
How can I delete them in keeping integrity in the database?
If someone could answer these questions, I thank him in advance.
Sincerly, Renaud THONNART
On Wed, May 09, 2001 at 10:31:27AM +0200, Renaud Thonnart wrote:
Does PostgreSQL create an index when a table is created?
Yes, with PK.
Does it create index even if there is no PK for this table?
No.
I know that indexes increase performance for SELECT but it is the
contrary when INSERT because the index must be actualised every time,
isn't it?
Yes.
How can I see all the index that PostgreSQL have implicitly create?
You can, from psql, do:
# \d table_name
This order shows all info about a table, including existing indexes.
How can I delete them in keeping integrity in the database?
drop index?...
Greets.
David
At 11:10 AM 5/9/01 +0200, DaVinci wrote:
On Wed, May 09, 2001 at 10:31:27AM +0200, Renaud Thonnart wrote:
How can I delete them in keeping integrity in the database?
drop index?...
Dropping the index will not maintain the PK integrity...
http://www.ca.postgresql.org/users-lounge/docs/7.1/reference/sql-createtable
.html
says:
PRIMARY KEY Constraint
Notes:
Postgres automatically creates a unique index to assure data integrity (see
CREATE INDEX statement).
Frank