Generic expression compiler for translation to provider specific SQL WHERE clauses. More...

#include <qgssqlexpressioncompiler.h>

Public Types
enum	Flag { CaseInsensitiveStringMatch = 1, LikeIsCaseInsensitive = 1 << 1, NoNullInBooleanLogic = 1 << 2, NoUnaryMinus = 1 << 3, IntegerDivisionResultsInInteger = 1 << 4 }
	Enumeration of flags for how provider handles SQL clauses. More...

enum	Result { None, Complete, Partial, Fail }
	Possible results from expression compilation. More...

Public Member Functions
	QgsSqlExpressionCompiler (const QgsFields &fields, QgsSqlExpressionCompiler::Flags flags=Flags())
	Constructor for expression compiler. More...

virtual	~QgsSqlExpressionCompiler ()=default

virtual Result	compile (const QgsExpression *exp)
	Compiles an expression and returns the result of the compilation. More...

virtual QString	result ()
	Returns the compiled expression string for use by the provider. More...

Protected Member Functions
virtual QString	castToInt (const QString &value) const
	Casts a value to a integer result. More...

virtual QString	castToReal (const QString &value) const
	Casts a value to a real result. More...

virtual Result	compileNode (const QgsExpressionNode *node, QString &str)
	Compiles an expression node and returns the result of the compilation. More...

virtual QString	quotedIdentifier (const QString &identifier)
	Returns a quoted column identifier, in the format expected by the provider. More...

virtual QString	quotedValue (const QVariant &value, bool &ok)
	Returns a quoted attribute value, in the format expected by the provider. More...

virtual QStringList	sqlArgumentsFromFunctionName (const QString &fnName, const QStringList &fnArgs) const
	Return the Arguments for SQL function for the expression function. More...

virtual QString	sqlFunctionFromFunctionName (const QString &fnName) const
	Return the SQL function for the expression function. More...

Protected Attributes
QgsFields	mFields

QString	mResult

Detailed Description

Generic expression compiler for translation to provider specific SQL WHERE clauses.

This class is designed to be overridden by providers to take advantage of expression compilation, so that feature requests can take advantage of the provider's native filtering support.

Since: QGIS 2.14

Note: Not part of stable API, may change in future versions of QGIS; Not available in Python bindings

Definition at line 39 of file qgssqlexpressioncompiler.h.

Member Enumeration Documentation

◆ Flag

enum QgsSqlExpressionCompiler::Flag

Enumeration of flags for how provider handles SQL clauses.

Enumerator
CaseInsensitiveStringMatch	Provider performs case-insensitive string matching for all strings.
LikeIsCaseInsensitive	Provider treats LIKE as case-insensitive.
NoNullInBooleanLogic	Provider does not support using NULL with boolean logic, e.g., "(...) OR NULL".
NoUnaryMinus	Provider does not unary minus, e.g., " -( 100 * 2 ) = ...".
IntegerDivisionResultsInInteger	Dividing int by int results in int on provider. Subclass must implement the castToReal() function to allow compilation of division.

Definition at line 55 of file qgssqlexpressioncompiler.h.

◆ Result

enum QgsSqlExpressionCompiler::Result

Possible results from expression compilation.

Enumerator
None	No expression.
Complete	Expression was successfully compiled and can be completely delegated to provider.
Partial	Expression was partially compiled, but provider will return extra records and results must be double-checked using QGIS' expression engine.
Fail	Provider cannot handle expression.

Definition at line 44 of file qgssqlexpressioncompiler.h.

Constructor & Destructor Documentation

◆ QgsSqlExpressionCompiler()

QgsSqlExpressionCompiler::QgsSqlExpressionCompiler	(	const QgsFields &	fields,
		QgsSqlExpressionCompiler::Flags	flags = `Flags()`
	)

explicit

Constructor for expression compiler.

Parameters

fields	fields from provider
flags	flags which control how expression is compiled

Definition at line 21 of file qgssqlexpressioncompiler.cpp.

◆ ~QgsSqlExpressionCompiler()

virtual QgsSqlExpressionCompiler::~QgsSqlExpressionCompiler ( )

virtualdefault

Member Function Documentation

◆ castToInt()

QString QgsSqlExpressionCompiler::castToInt ( const QString & value ) const

protectedvirtual

Casts a value to a integer result.

Subclasses must reimplement this to cast a numeric value to a integer type value so that integer division results in a integer value result instead of real.

Since: QGIS 3.0

Definition at line 412 of file qgssqlexpressioncompiler.cpp.

◆ castToReal()

QString QgsSqlExpressionCompiler::castToReal ( const QString & value ) const

protectedvirtual

Casts a value to a real result.

Subclasses which indicate the IntegerDivisionResultsInInteger flag must reimplement this to cast a numeric value to a real type value so that division results in a real value result instead of integer.

Since: QGIS 3.0

Definition at line 406 of file qgssqlexpressioncompiler.cpp.

◆ compile()

QgsSqlExpressionCompiler::Result QgsSqlExpressionCompiler::compile ( const QgsExpression * exp )

virtual

Compiles an expression and returns the result of the compilation.

Definition at line 28 of file qgssqlexpressioncompiler.cpp.

◆ compileNode()

QgsSqlExpressionCompiler::Result QgsSqlExpressionCompiler::compileNode	(	const QgsExpressionNode *	node,
		QString &	str
	)

protectedvirtual

Compiles an expression node and returns the result of the compilation.

Parameters

node	expression node to compile
str	string representing compiled node should be stored in this parameter

Returns: result of node compilation

Definition at line 77 of file qgssqlexpressioncompiler.cpp.

◆ quotedIdentifier()

QString QgsSqlExpressionCompiler::quotedIdentifier ( const QString & identifier )

protectedvirtual

Returns a quoted column identifier, in the format expected by the provider.

Derived classes should override this if special handling of column identifiers is required.

See also: quotedValue()

Definition at line 41 of file qgssqlexpressioncompiler.cpp.

◆ quotedValue()

QString QgsSqlExpressionCompiler::quotedValue	(	const QVariant &	value,
		bool &	ok
	)

protectedvirtual

Returns a quoted attribute value, in the format expected by the provider.

Derived classes should override this if special handling of attribute values is required.

Parameters

value	value to quote
ok	wil be set to true if value can be compiled

See also: quotedIdentifier()

Definition at line 49 of file qgssqlexpressioncompiler.cpp.

◆ result()

QString QgsSqlExpressionCompiler::result ( )

virtual

Returns the compiled expression string for use by the provider.

Definition at line 36 of file qgssqlexpressioncompiler.cpp.

◆ sqlArgumentsFromFunctionName()

QStringList QgsSqlExpressionCompiler::sqlArgumentsFromFunctionName	(	const QString &	fnName,
		const QStringList &	fnArgs
	)		const

protectedvirtual

Return the Arguments for SQL function for the expression function.

Derived classes should override this to help compile functions

Parameters

fnName	expression function name
fnArgs	arguments from expression

Returns: the arguments updated for SQL Function

Definition at line 400 of file qgssqlexpressioncompiler.cpp.

◆ sqlFunctionFromFunctionName()

QString QgsSqlExpressionCompiler::sqlFunctionFromFunctionName ( const QString & fnName ) const

protectedvirtual

Return the SQL function for the expression function.

Derived classes should override this to help compile functions

Parameters

fnName expression function name

Returns: the SQL function name

Definition at line 394 of file qgssqlexpressioncompiler.cpp.

Member Data Documentation

◆ mFields

QgsFields QgsSqlExpressionCompiler::mFields

protected

Definition at line 143 of file qgssqlexpressioncompiler.h.

◆ mResult

QString QgsSqlExpressionCompiler::mResult

protected

Definition at line 142 of file qgssqlexpressioncompiler.h.

The documentation for this class was generated from the following files:

/tmp/buildd/qgis-3.0.2+14stretch/src/core/qgssqlexpressioncompiler.h
/tmp/buildd/qgis-3.0.2+14stretch/src/core/qgssqlexpressioncompiler.cpp

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

◆ Flag

◆ Result

Constructor & Destructor Documentation

◆ QgsSqlExpressionCompiler()

◆ ~QgsSqlExpressionCompiler()

Member Function Documentation

◆ castToInt()

◆ castToReal()

◆ compile()

◆ compileNode()

◆ quotedIdentifier()

◆ quotedValue()

◆ result()

◆ sqlArgumentsFromFunctionName()

◆ sqlFunctionFromFunctionName()

Member Data Documentation

◆ mFields

◆ mResult