Rocker — rocksdb driver for Erlang

Maxim Molchanov
Sep 14, 2018 · 5 min read

Brief overview of current solutions


API overview

Open database

{ok, Db} = rocker:open_default(<<”/project/priv/db_default_path”>>).
{ok, Db} = rocker:open(<<"/project/priv/db_path">>, #{create_if_missing => true,set_max_open_files => 1000,set_use_fsync => false,...set_disable_auto_compactions => true,set_compaction_style => universal}).
{ok, Db} = case rocker:list_cf(BookDbPath) of{ok, CfList} ->   rocker:open_cf_default(BookDbPath, CfList);_ ->   CfList = [],   rocker:open_default(BookDbPath)end.

Delete database

Recover database after a failure

Column family creation

rocker:create_cf_default(Db, <<”testcf1">>) -> ok.

Column family deletion

rocker:drop_cf(Db, <<”testcf”>>) -> ok.

CRUD operations

Data writing by key

rocker:put(Db, <<”key”>>, <<”value”>>) -> ok.

Data acquisition by key

rocker:get(Db, <<”key”>>) -> {ok, <<”value”>>} | notfound

Data deletion by key

rocker:delete(Db, <<”key”>>) -> ok.

Data writing by key within CF

rocker:put_cf(Db, <<”testcf”>>, <<”key”>>, <<”value”>>) -> ok.

Data acquisition by key within CF

rocker:get_cf(Db, <<”testcf”>>, <<”key”>>) -> {ok, <<”value”>>} | notfound

Data deletion by key within CF

rocker:delete_cf(Db, <<”testcf”>>, <<”key”>>) -> ok,


Create iterator

rocker:iterator(Db, {‘start’}) -> {ok, Iter}.

Check iterator

rocker:iterator_valid(Iter) -> {ok, true} | {ok, false}.

Create iterator for CF

rocker:iterator_cf(Db, Cf, {‘start’}) -> {ok, Iter}.

Create prefix iterator

{ok, Db} = rocker:open(Path, #{prefix_length => 3}).
{ok, Iter} = rocker:prefix_iterator(Db, <<”aaa”>>),

Create prefix iterator for CF

{ok, Iter} = rocker:prefix_iterator_cf(Db, Cf, <<”aaa”>>),

Get the following element

rocker:next(Iter) -> {ok, <<”key”>>, <<”value”>>} | ok


{ok, 6} = rocker:tx(Db, [   {put, <<"k1">>, <<"v1">>},   {put, <<"k2">>, <<"v2">>},   {delete, <<"k0">>, <<"v0">>},   {put_cf, Cf, <<"k1">>, <<"v1">>},   {put_cf, Cf, <<"k2">>, <<"v2">>},   {delete_cf, Cf, <<"k0">>, <<"v0">>}]).



Maxim Molchanov

Written by

Senior Software Engineer at, MS, PGCHE

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