Simple simulation of NoSQL database written in java.

Features

• data model similar to Apache Cassandra (http://wiki.apache.org/cassandra/DataModel). Keyspace contains column families, column families are sets of key:row, where row is set of key:value pair called column
• simple language PQL (pythia query language). Provides basic (really basic) commands to manage keyspaces, column families etc.
• server and basic client (it's only simulation)

Most interesting things to watch

• PQL lexer/parser/compiler source code

PQL

Commands

• KEYSPACE <name> - creates keyspace (value must be unique)
• KILL <name> - drop of keyspace
• USE <name> - chooses keyspace to use
• CREATE COLUMNFAMILY <name> - creates new column family in actual keyspace (value must be unique in keyspace)
• DROP COLUMNFAMILY <name> - drops column family
• INSERT INTO <columnfamily> (KEY=<val>,<column>=<value>...) - insert row to column family, where KEY is unique index of row
• DELETE FROM <columnfamily> WHERE KEY=<val> - delete row indexed by KEY from column family
• UPDATE <columnfamily> SET KEY=<val>,<column>=<value>... WHERE KEY=<value> - update row columns in column family
• SELECT FROM <columnfamily> WHERE KEY=<value> - select row data from column family, returns data in JSON format

LL(1) grammar of PQL

<create_keyspace_stmt> ::= <KEYSPACE> <VAR>
<drop_keyspace_stmt> ::= <KILL> <VAR>
<use_keyspace_stmt> ::= <USE> <VAR>
<create_columnfamily_stmt> ::= <CREATE> <COLUMNFAMILY> <VAR>
<drop_columnfamily_stmt> ::= <DROP> <COLUMNFAMILY> <VAR>
<key_values_list'> ::= ,<var><key_values_list'>|Epsilon
<key_values_list> ::= <KEY>=<VAR><key_values_list'>
<insert_stmt> ::= <INSERT><INTO><VAR>(<key_values_list>)
<where_stmt> ::= <WHERE><KEY>=<VAR>
<update_stmt> ::= <UPDATE><VAR><SET><key_values_list>
<delete_stmt> ::= <DELETE><FROM><VAR><where_stmt>
<select_stmt> ::= <SELECT><FROM><VAR><where_stmt>
<start_stmt> ::= <create_keyspace_stmt> | <drop_keyspace_stmt> |
<use_keyspace_stmt> | <create_columnfamily_stmt> |
<drop_columnfamily_stmt> | <insert_stmt> | <update_stmt> |
<delete_stmt> | <select_stmt>
<VAR> ::= [a-zA-Z]+ | "[.]*"
<KEYSPACE> ::= KEYSPACE
<KILL> ::= KILL
<USE> ::= USE
<CREATE> ::= CREATE
<COLUMNFAMILY> ::= COLUMNFAMILY
<DROP> ::= DROP
<KEY> ::= KEY
<INSERT> ::= INSERT
<INTO> ::= INTO
<WHERE> ::= WHERE
<UPDATE> ::= UPDATE
<SET> ::= SET
<DELETE> ::= DELETE
<FROM> ::= FROM
<SELECT> ::= SELECT