enumerateIndexedValuesInColumn.m

- (BOOL)_enumerateIndexedValuesInColumn:(NSString *)column matchingQuery:(YapDatabaseQuery *)query
						   usingBlock:(void (^)(id indexedValue, BOOL *stop))block
{
	if (column == nil) return NO;
	if (query == nil) return NO;
	if (query.isAggregateQuery) return NO;

	// Create full query using given filtering clause(s)

	NSString *fullQueryString =
	[NSString stringWithFormat:@"SELECT \"%@\" AS IndexedValue FROM \"%@\" %@;", column, [self tableName], query.queryString];

	// Turn query into compiled sqlite statement (using cache if possible)

	sqlite3_stmt *statement = [self prepareQueryString:fullQueryString];
	if (statement == NULL)
	{
		return NO;
	}

	// Bind query parameters appropriately.

	[self bindQueryParameters:query.queryParameters forStatement:statement withOffset:SQLITE_BIND_START];

	// Enumerate query results

	BOOL stop = NO;
	YapMutationStackItem_Bool *mutation = [parentConnection->mutationStack push]; // mutation during enum protection

	int status = sqlite3_step(statement);
	if (status == SQLITE_ROW)
	{
		if (databaseTransaction->connection->needsMarkSqlLevelSharedReadLock)
			[databaseTransaction->connection markSqlLevelSharedReadLockAcquired];

		int columnType = sqlite3_column_type(statement, SQLITE_COLUMN_START);
		id indexedValue;

		do
		{
			switch(columnType) {
				case SQLITE_INTEGER:
				{
					int64_t value = sqlite3_column_int64(statement, SQLITE_COLUMN_START);
					indexedValue = @(value);
					break;
				}

				case SQLITE_FLOAT:
				{
					double value = sqlite3_column_double(statement, SQLITE_COLUMN_START);
					indexedValue = @(value);
					break;
				}

				case SQLITE_TEXT:
				{
					const unsigned char *text = sqlite3_column_text(statement, SQLITE_COLUMN_START);
					int textSize = sqlite3_column_bytes(statement, SQLITE_COLUMN_START);
					indexedValue = [[NSString alloc] initWithBytes:text length:textSize encoding:NSUTF8StringEncoding];
					break;
				}

				case SQLITE_BLOB:
				{
					const void *value = sqlite3_column_blob(statement, SQLITE_COLUMN_START);
					int valueSize = sqlite3_column_bytes(statement, SQLITE_COLUMN_START);
					indexedValue = [[NSData alloc] initWithBytes:value length:valueSize];
					break;
				}
			}

			block(indexedValue, &stop);

			if (stop || mutation.isMutated) break;

		} while ((status = sqlite3_step(statement)) == SQLITE_ROW);
	}

	if ((status != SQLITE_DONE) && !stop && !mutation.isMutated)
	{
		YDBLogError(@"%@ - sqlite_step error: %d %s", THIS_METHOD,
					status, sqlite3_errmsg(databaseTransaction->connection->db));
	}

	sqlite3_clear_bindings(statement);
	sqlite3_reset(statement);

	if (!stop & mutation.isMutated)
	{
		@throw [self mutationDuringEnumerationException];
	}

	return (status == SQLITE_DONE);
}

- (BOOL)enumerateIndexedValuesInColumn:(NSString *)column matchingQuery:(YapDatabaseQuery *)query usingBlock:(void(^)(id indexedValue, BOOL *stop))block
{
	BOOL result = [self _enumerateIndexedValuesInColumn:column matchingQuery:query usingBlock:^(id indexedValue, BOOL *stop) {

		if (block == NULL) // Query test : caller still wants BOOL result
		{
			*stop = YES;
			return; // from block
		}

		block(indexedValue, stop);
	}];

	return result;
}