QgsSqlExpressionCompiler Class Reference

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

#include <qgssqlexpressioncompiler.h>

Public Types
enum	Flag { CaseInsensitiveStringMatch = 0x01, LikeIsCaseInsensitive = 0x02, NoNullInBooleanLogic = 0x04, NoUnaryMinus = 0x08 }
	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, const Flags &flags=Flags())
	Constructor for expression compiler. More...
virtual	~QgsSqlExpressionCompiler ()
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 Result	compileNode (const QgsExpression::Node *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...

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.

Note

Added in version 2.14

Not part of stable API, may change in future versions of QGIS

Not available in Python bindings

Definition at line 33 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, eg "(...) OR NULL".
NoUnaryMinus	Provider does not unary minus, eg " -( 100 * 2 ) = ...".

Definition at line 48 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 38 of file qgssqlexpressioncompiler.h.

Constructor & Destructor Documentation

QgsSqlExpressionCompiler()

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

explicit

Constructor for expression compiler.

Parameters

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

Definition at line 18 of file qgssqlexpressioncompiler.cpp.

~QgsSqlExpressionCompiler()

QgsSqlExpressionCompiler::~QgsSqlExpressionCompiler ( )

virtual

Definition at line 25 of file qgssqlexpressioncompiler.cpp.

Member Function Documentation

compile()

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

virtual

Compiles an expression and returns the result of the compilation.

Definition at line 30 of file qgssqlexpressioncompiler.cpp.

compileNode()

QgsSqlExpressionCompiler::Result QgsSqlExpressionCompiler::compileNode ( const QgsExpression::Node *  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 74 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 38 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 46 of file qgssqlexpressioncompiler.cpp.

result()

virtual QString QgsSqlExpressionCompiler::result ( )

inlinevirtual

Returns the compiled expression string for use by the provider.

Definition at line 70 of file qgssqlexpressioncompiler.h.

Member Data Documentation

mFields

QgsFields QgsSqlExpressionCompiler::mFields

protected

Definition at line 97 of file qgssqlexpressioncompiler.h.

mResult

QString QgsSqlExpressionCompiler::mResult

protected

Definition at line 96 of file qgssqlexpressioncompiler.h.

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

• /tmp/buildd/qgis-2.18.21+99unstable/src/core/qgssqlexpressioncompiler.h
• /tmp/buildd/qgis-2.18.21+99unstable/src/core/qgssqlexpressioncompiler.cpp