org.apache.derby.iapi.services.daemon
Interface IndexStatisticsDaemon

All Known Implementing Classes:

IndexStatisticsDaemonImpl

public interface IndexStatisticsDaemon

Daemon acting as a coordinator for creating and updating index statistics.

There are two modes of operation:

• explicit - generates index statistics due to an explict request from the user. The entrypoint is runExplicitly.
• background - generates index statistics as a background task due to an event that has triggered a statistics update. The entrypoint is schedule.

The modes differ in how the operation affects other operations in the running system, and also how errors are dealt with. The background mode will try to affect other operations as little as possible, and errors won't be reported unless they are severe. The explicit mode will do more to make sure the operation succeeds (for instance by using locks), and will report all errors.

Method Summary

void	runExplicitly(LanguageConnectionContext lcc, TableDescriptor td, ConglomerateDescriptor[] cds, java.lang.String runContext) Creates/updates index statistics for the specified conglomerates/indexes.
void	schedule(TableDescriptor td) Schedules creation/update of the index statistics associated with the specified table.
void	stop() Stops the background daemon.

Method Detail

runExplicitly

void runExplicitly(LanguageConnectionContext lcc,
                   TableDescriptor td,
                   ConglomerateDescriptor[] cds,
                   java.lang.String runContext)
                   throws StandardException

Creates/updates index statistics for the specified conglomerates/indexes.

Parameters:

lcc - connection used to carry out the work

td - base table

cds - index conglomerates (non-index conglomerates are ignored)

runContext - descriptive text for the context in which the work is being run (i.e. ALTER TABLE)

Throws:

StandardException - if something goes wrong

schedule

void schedule(TableDescriptor td)

Schedules creation/update of the index statistics associated with the specified table.

Note that the scheduling request may be denied. Typical situations where that will happen is if the work queue is full, or if work has already been scheduled for the specified table.

Parameters:

td - base table

stop

void stop()

Stops the background daemon.

Any ongoing tasks will be aborted as soon as possible, and it will not be possible to schedule new tasks. Note that runExplicitly can still be used.