Share etx indexes

The etx indexes are to be left open to improve performance of subsequent queries that use the index.

The first time an etx index is used in a query (opened), resources such as shared memory are allocated in the database server, and these resources continue to be allocated after the query has finished executing. This causes the first query that opens the etx index to run slower than subsequent user sessions that use these already-opened resources.

When opened, an etx index does not automatically free the shared resources until the database server shuts down. An etx index does free shared resources after an update, insertion, or deletion to the table, or during a rollback of a transaction that uses the index. If you must free resources, you can force an etx index to close by executing the etx_CloseIndex() routine. Be aware, however, that the next user who reopens the etx index again incurs the initial cost of storing index information in memory.