/**
* Check and purge committed deleted rows on a page.
*
* <p>
*
* @return true, if no purging has been done on page, and thus latch can be released before end
* transaction. Otherwise the latch on the page can not be released before commit.
* @param page A non-null, latched page must be passed in. If all rows on page are purged, then
* page will be removed and latch released.
* @exception StandardException Standard exception policy.
*/
protected final boolean purgeCommittedDeletes(Page page) throws StandardException {
boolean purgingDone = false;
// The number records that can be reclaimed is:
// total recs - recs_not_deleted
int num_possible_commit_delete = page.recordCount() - page.nonDeletedRecordCount();
if (num_possible_commit_delete > 0) {
// loop backward so that purges which affect the slot table
// don't affect the loop (ie. they only move records we
// have already looked at).
for (int slot_no = page.recordCount() - 1; slot_no >= 0; slot_no--) {
boolean row_is_committed_delete = page.isDeletedAtSlot(slot_no);
if (row_is_committed_delete) {
// At this point we only know that the row is
// deleted, not whether it is committed.
// see if we can purge the row, by getting an
// exclusive lock on the row. If it is marked
// deleted and we can get this lock, then it
// must be a committed delete and we can purge
// it.
RecordHandle rh =
page.fetchFromSlot(
(RecordHandle) null,
slot_no,
RowUtil.EMPTY_ROW,
RowUtil.EMPTY_ROW_FETCH_DESCRIPTOR,
true);
row_is_committed_delete = this.lockRowAtSlotNoWaitExclusive(rh);
if (row_is_committed_delete) {
purgingDone = true;
page.purgeAtSlot(slot_no, 1, false);
}
}
}
}
if (page.recordCount() == 0) {
// Deallocate the current page with 0 rows on it.
this.removePage(page);
// removePage guarantees to unlatch the page even if an
// exception is thrown. The page is protected against reuse
// because removePage locks it with a dealloc lock, so it
// is OK to release the latch even after a purgeAtSlot is
// called.
// @see ContainerHandle#removePage
purgingDone = true;
}
return (purgingDone);
}
