View Source erlfdb_range_iterator (erlfdb v0.3.4)

An iterator interface over GetRange and GetMappedRange.

The iterator is an alternative implmentation to erlfdb:get_range/4 and erlfdb:wait_for_all_interleaving/3. The database mechanics are equivalent, but the iterator allows you to control when each wait actually happens.

Remember that FoundationDB transaction execution time is limited to 5 seconds, so you must take care not to delay your iteration.

To use the iterator,

erlfdb_range_iterator:start/4: Sends the first GetRange request to the database server.
erlfdb_iterator.next/1: Waits for the result of the GetRange request. Then issues another GetRange request to the database server.
erlfdb_iterator.stop/1: Cancels the active future, if one exists.

Summary

Types

page()

state()

Functions

get_future/1

Gets the active future from the iterator's internal state.

handle_next/1

handle_stop/1

start(Tx, StartKey, EndKey)

Starts the iterator.

start(Tx, StartKey, EndKey, Options)

Starts the iterator.

Types

page()

-type page() :: [erlfdb:kv()] | [erlfdb:mapped_kv()].

state()

-type state() ::
          #state{tx :: term(),
                 start_key :: term(),
                 end_key :: term(),
                 mapper :: term(),
                 limit :: term(),
                 target_bytes :: term(),
                 streaming_mode :: term(),
                 iteration :: term(),
                 snapshot :: term(),
                 reverse :: term(),
                 future :: term()}.

Functions

get_future/1

-spec get_future(state()) -> undefined | erlfdb:future().

Gets the active future from the iterator's internal state.

You needn't call this function for normal use of the iterator.

handle_next/1

-spec handle_next(state()) -> {halt, state()} | {cont, [page()], state()}.

handle_stop/1

-spec handle_stop(state()) -> ok.

start(Tx, StartKey, EndKey)

-spec start(erlfdb:transaction(), erlfdb:key(), erlfdb:key()) -> erlfdb_iterator:iterator().

Starts the iterator.

Equivalent to start(Tx, StartKey, EndKey, []).

start(Tx, StartKey, EndKey, Options)

-spec start(erlfdb:transaction(), erlfdb:key(), erlfdb:key(), [erlfdb:fold_option()]) ->
               erlfdb_iterator:iterator().

Starts the iterator.

Sends the first GetRange request to the database server.