Method seek_impl

fdbserver/VersionedBTree.actor.cpp:7513–7545

		// If non-zero is returned then the cursor is valid and the return value is logically equivalent
		// to query.compare(cursor.get())
		ACTOR Future<int> seek_impl(BTreeCursor* self, RedwoodRecordRef query) {
			state RedwoodRecordRef internalPageQuery = query.withMaxPageID();
			self->path.resize(1);
			debug_printf("seek(%s) start cursor = %s\n", query.toString().c_str(), self->toString().c_str());

			loop {
				auto& entry = self->path.back();
				if (entry.btPage()->isLeaf()) {
					int cmp = entry.cursor.seek(query);
					self->valid = entry.cursor.valid() && !entry.cursor.isErased();
					debug_printf("seek(%s) loop exit cmp=%d cursor=%s\n",
					             query.toString().c_str(),
					             cmp,
					             self->toString().c_str());
					return self->valid ? cmp : 0;
				}

				// Internal page, so seek to the branch where query must be
				// Currently, after a subtree deletion internal page boundaries are still strictly adhered
				// to and will be updated if anything is inserted into the cleared range, so if the seek fails
				// or it finds an entry with a null child page then query does not exist in the BTree.
				if (entry.cursor.seekLessThan(internalPageQuery) && entry.cursor.get().value.present()) {
					debug_printf(
					    "seek(%s) loop seek success cursor=%s\n", query.toString().c_str(), self->toString().c_str());
					Future<Void> f = self->pushPage(entry.cursor);
					wait(f);
				} else {
					self->valid = false;
					debug_printf(
					    "seek(%s) loop exit cmp=0 cursor=%s\n", query.toString().c_str(), self->toString().c_str());
					return 0;
				}
			}
		}

		Future<int> seek(RedwoodRecordRef query) { return path.empty() ? 0 : seek_impl(this, query); }