/**
* Remove a page.
*
* @param pos the position of the page
* @param memory the memory usage
*/
void removePage(long pos, int memory) {
// we need to keep temporary pages,
// to support reading old versions and rollback
if (pos == 0) {
// the page was not yet stored:
// just using "unsavedMemory -= memory" could result in negative
// values, because in some cases a page is allocated, but never
// stored, so we need to use max
unsavedMemory = Math.max(0, unsavedMemory - memory);
return;
}
// This could result in a cache miss if the operation is rolled back,
// but we don't optimize for rollback.
// We could also keep the page in the cache, as somebody
// could still read it (reading the old version).
if (cache != null) {
if (DataUtils.getPageType(pos) == DataUtils.PAGE_TYPE_LEAF) {
// keep nodes in the cache, because they are still used for
// garbage collection
cache.remove(pos);
}
}
BTreeChunk chunk = getChunk(pos);
long maxLengthLive = DataUtils.getPageMaxLength(pos);
// synchronize, because pages could be freed concurrently
synchronized (chunk) {
chunk.maxLenLive -= maxLengthLive;
chunk.pageCountLive--;
chunk.changed = true;
}
}
