SQL-DotNet

Sql dot is a library which allows, to embed your own sql engine (parser, compiler and runtime) into your .net application. The parser is completly written using c# and available under the MIT license.

Initialy the parser is written for the ODBC-Driver used by the Simplic Content Delivery Network and is set as open source project, to let other benefit from this project and create some great sql-implementation togehter.

Aim

The aim is, to create a library which allows to embed sql in your appliaction, only by implementing a single interface: IQueryExecutor. The complete communication with your software is written in this implementation and registered in one line.

Implementation

public class MyQueryExecutor : IQueryExecutor
{
    // ...
}

Registration

// Register the query executor
SqlDotNet.Sql.RegisterExecutor<MyQueryExecutor>()

General things to know

SIQL

SIQL - Structured Intermidiate Query Lanugage. All sql queries will be compiled into this simple language before execution. This language is similar to .net IL code and other intermedate languages.

Short example: SELECT Ident, Name, ValueInCent * 100 as Dollar FROM Products WHERE Name = 'Ski'

// SQL program

@siql v1

ocur.tbl cur1
curout.cur1 ()
cursrc.cur1 Products
filter cur1
{
	ldcol Name
	ldc.str 'Ski'
	eq
}
oresset res1
fresset.res1 (cur1)
{
	crow
	ldcol Ident
	pnxc __col0
	ldcol Name
	pnxc __col1
	ldcol ValueInCent
	ldc.i4 100
	mul
	pnxc Dollar
}

Library structure

The library is structured into a compiler and runtime. Both with be explained in this article, to get an overview. The library is under heavy development, so changes are maybe not up-to-date here.

Compiler pipeline

The compiler compiles a sql query into SIQL code and cache it. If the same query will be executed later, it has not to be compiled again. The compiler is splitted into the following steps.

Debugger

We are also creating some debugger tool. The debugger is not directly for debugging SQL-Statements, but for debugging the Compiler and runtime, because it visualize all generated results.

Tokenizer

The tokenizer takes the input sql code and makes build tokens. E.g.: SELECT A FROM B will be splitted into <SELECT> <A> <FROM> <B>.

Involved files

1. /Compiler/Tokenizer/Tokenizer.cs Tokenizer core
2. /Compiler/Tokenizer/ParserConfiguration.cs Configuration files for token generating

Syntax-Tree-Builder (AST)

The syntaxtree builder classifies all token in the Build method and creates the Abstract-Syntax-Tree (AST). In this steps first Sql sematic analysis will be done. The result is a tree build of SyntaxTreeNodes. Also conditions and other expressions will be resolved using the Shuntig-Yard algorithm.

Involved files

1. /Compiler/SyntaxTree/SyntaxTreeBuilder.cs Main tree builder
2. /Compiler/SyntaxTree/Nodes/* All node definitions
3. /Compiler/SyntaxTree/Factory/SyntaxTreeFactory.cs Token classification
4. /Compiler/SyntaxTree/ShuntingYard.cs Shunting Yard algorithm

Sematic-Analysis

Not yet implemented

SIQL-Generator/Compiler

Takes the optimized and generated AST and compiles it to SIQL code.

1. /Compiler/ILCompiler/SIQLCompiler.cs Main compiler

Runtime

The runtime is responsible to execute SIQL code and call the IQueryExecutor interface/implementation.

The runtime is implemeted in SQLRuntime.cs and contains the execution ligic which triggers the IQueryExecutor. The required components for the runtime are all placed in the Runtime/ directory and consists of:

1. CommandChain - SIQL as .net commands
2. Scope - Contains the scope-system, for holding cursor, resultsets, arguments and other stuff
3. Stack - Used for operation and resultset generating
4. CLRInterface - Contains the communication interface to invoke methods when sql functions or statements were executed.