# Functions
DoParallelQueries translates between our interface for query batching, and indexes that don't yet support batching.
EnsureDirectory makes sure directory is there, if not creates it if not.
GetParallelChunks fetches chunks in parallel (up to maxParallel).
# Variables
QueryParallelism is the maximum number of subqueries run in parallel per higher-level query.
# Structs
ReadCloserWithContextCancelFunc helps with cancelling the context when closing a ReadCloser.
# Type aliases
DoSingleQuery is the interface for indexes that don't support batching yet.