ThistleDB - Simple JSON Database

Simple JSON database based on the file-access and server-client approach with the non-blocking server and the reactive (asynchronous non-blocking) client.

Prerequisites

• Java 8
• Maven

Get Started

First, clone or fork the repository:

$ git clone git@github.com:ttulka/thistledb.git
$ cd thistledb

Now build it and assemble:

$ mvn clean install -P localBuild
$ mvn package appassembler:assemble --file server-app/pom.xml

And finally run it:

$ cd server-app/target/server/bin
$ server

Type your command/query ending with ; or stop the server and exit the console by typing quit.

Data Structures

ThistleDB is based on the file-access. All the data are persistent on a disk.

Collections

Collections are separated data spaces with schema-less structures.

A collection contains a set of documents.

Collection name can contain only literals, digits and underscore _.

Documents

Documents are JSON objects in a collection.

Elements

Elements are paths in a document.

Example (patient.name is an element addressing a patient name in the document):

{
    "patient" : {
        "id" : "123456789",
        "name" : "John Smith"
    }
}

Name of an element can contain literals, digits, underscore _ and dash -.

Example of valid element names:

name
123
patient-name_123

Values

Values could be strings, numbers, boolean literals and null.

Commands and Queries

All the commands and queries are SQL-like.

Create a Collection

CREATE collection_name 

Drop a Collection

DROP collection_name 

Add an Element to Documents in a Collection

ALTER collection_name ADD element [WHERE element op value [{AND|OR} element op value [...]]]  

Remove an Element from Documents in a Collection

ALTER collection_name REMOVE element [WHERE element op value [{AND|OR} element op value [...]]]  

Insert a Document into a Collection

INSERT INTO collection_name VALUES json_document[,json_document[...]]

Select a Document from a Collection

SELECT {*|element[,element[...]]} FROM collection_name [WHERE element=value [{AND|OR} element=value [...]]]  

Delete a Document from a Collection

DELETE FROM collection_name [WHERE element op value [{AND|OR} element op value [...]]]  

Update a Document in a Collection

UPDATE collection_name SET element=value[,element=value [...]] [WHERE element op value [{AND|OR} element op value [...]]]  

Element is updated only when exists.

Operators

Operator	Meaning	Note
=	Equal
!=	Not equal
>	Greater
>=	Greater or equal
<	Less
<=	Less or equal
LIKE	Equal by an expression	* any string, _ one character, ? any character (0,1)

Indexes

For accelerating the speed of searching can be used indexes on a collection.

Only simple-value elements (numbers, strings, ...) can be indexed. Indexes are applied only on conditions with the equals operator =.

As usual, indexes accelerate reading but degrading speed of data modifications - use them cleverly!

Create an Index for a Collection

CREATE INDEX indexed_element ON collection_name  

Drop an Index for a Collection

DROP INDEX indexed_element ON collection_name  

DUAL Collection

DUAL collection is an immutable system "echo" collection which returns what it gets.

Query	Result
SELECT 123 FROM dual	{ "value" : 123 }
SELECT 1.23 FROM dual	{ "value" : 1.23 }
SELECT true FROM dual	{ "value" : true }
SELECT "abc" FROM dual	{ "value" : "abc" }

There are special element to be returned.

Query	Result	Example
SELECT * FROM dual	empty	{}
SELECT name FROM dual	name of the collection	{ "name" : "DUAL" }
SELECT random FROM dual	a random integer	{ "random" : -980456651 }
SELECT date FROM dual	datetime in format yyyy-mm-dd H:m:s.ms	{ "date" : "2017-02-19 14:25:02.122" }

Client

ThistleDB provides a Java driver to build a client from a Java application.

Client implements Reactive Streams, Version 1.0.0.

Client is not thread-safe, to ensure concurrency must be run within a synchronized context.

Copy the Maven dependency into your project:

<dependency>
    <groupId>cz.net21.ttulka.thistledb</groupId>
    <artifactId>thistledb-client</artifactId>
    <version>1.0.0</version>
</dependency>

Open a client connection:

import cz.net21.ttulka.thistledb.client.Client;
// ...
Client client = new Client("localhost", 9658);

Create a collection:

client.executeCommand("CREATE test");

Put a document into the collection:

String json = "{\"patient\" : {\"id\" : \"123456789\", \"name\" : \"John Smith\"} }";
client.executeCommand("INSERT INTO test VALUES " + json);

Select the document from the collection (blocking):

String query = "SELECT * FROM test WHERE patient.id='123456789'";
List<String> result = client.executeQueryBlocking(query);

result.forEach(json -> System.out.println(json));

Select the document from the collection (non-blocking):

client.executeQuery(query).subscribe(System.out::println);

Close the client:

client.close();

Server

Default server port is 9658.

Default data folder is data, the path relative to the executing directory.

Maximum client connections the server accepts is 20.

Server can be started from the command-line or dynamically from a Java code.

Starting from a Command-Line

After downloading binaries or compiling from the source code (see Get Started) run the server from the command-line:

$ cd server-app/target/server/bin
$ server

Changing the Default Port

-p, --port <port>

Changing the Default Data Folder

-d, --dataDir <path>

Maximum Client Connections

-m, --maxConnections <maximum>

Caching

-c, --cacheExpirationTime <minutes>

Caching is active only together with indexes. Default value is 20 minutes, zero value means no caching.

Starting from a Java Code

Copy the Maven dependency into your project:

<dependency>
    <groupId>cz.net21.ttulka.thistledb</groupId>
    <artifactId>thistledb-server</artifactId>
    <version>...</version>
</dependency>

Create a server instance

For creating a new server object use ServerBuilder:

Server.ServerBuilder builder = Server.builder();
Server server = builder.build();

Set the port:

int port = 1234;
Server server = Server.builder().port(port).build();

Set the data folder:

Path dataFolder = java.nio.file.Paths.get("/data");
Server server = Server.builder().dataFolder(dataFolder).build();

Set the cache expiration time (in minutes):

int cacheExpirationTime = 0;    // zero means cache is disabled
Server server = Server.builder().cacheExpirationTime(cacheExpirationTime).build();

Setters can be mixed as wanted:

Server server = Server.builder().port(1234).cacheExpirationTime(5).build();

Maximum client connections can be changed by a setter:

int maxClientConnections = 10;
server.setMaxClientConnections(maxClientConnections);

Start and stop the server

server.start();
server.stop();

Console

Console provides a remote access to the server from a command-line.

First, build it and assemble:

$ mvn clean install -P localBuild
$ mvn package appassembler:assemble --file console-app/pom.xml

And run it:

$ cd console-app/target/console/bin
$ console

Type your command/query ending with ; or exit the console by typing quit.

License

Apache License, Version 2.0