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Create QgsSqlExpressionCompiler as base class for expression compilers
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Switch Postgres and OGR compilers to use the new base class. New class
should make it easier to add additional expression compilers (eg
spatialite, MS SQL, etc)
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@nyalldawson
nyalldawson committed Nov 18, 2015
1 parent f7ed42b commit 5f65f87
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Showing 8 changed files with 427 additions and 397 deletions.
2 changes: 2 additions & 0 deletions src/core/CMakeLists.txt
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Expand Up @@ -178,6 +178,7 @@ SET(QGIS_CORE_SRCS
qgssnapper.cpp
qgssnappingutils.cpp
qgsspatialindex.cpp
qgssqlexpressioncompiler.cpp
qgsstatisticalsummary.cpp
qgsstringutils.cpp
qgstransaction.cpp
Expand Down Expand Up @@ -624,6 +625,7 @@ SET(QGIS_CORE_HDRS
qgssnapper.h
qgssnappingutils.h
qgsspatialindex.h
qgssqlexpressioncompiler.h
qgsstatisticalsummary.h
qgsstringutils.h
qgstolerance.h
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280 changes: 280 additions & 0 deletions src/core/qgssqlexpressioncompiler.cpp
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/***************************************************************************
qgssqlexpressioncompiler.cpp
----------------------------
begin : November 2015
copyright : (C) 2015 Nyall Dawson
email : nyall dot dawson at gmail dot com
***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************/

#include "qgssqlexpressioncompiler.h"

QgsSqlExpressionCompiler::QgsSqlExpressionCompiler( const QgsFields& fields, const Flags& flags )
: mResult( None )
, mFields( fields )
, mFlags( flags )
{
}

QgsSqlExpressionCompiler::~QgsSqlExpressionCompiler()
{

}

QgsSqlExpressionCompiler::Result QgsSqlExpressionCompiler::compile( const QgsExpression* exp )
{
if ( exp->rootNode() )
return compile( exp->rootNode(), mResult );
else
return Fail;
}

QString QgsSqlExpressionCompiler::quotedIdentifier( const QString& identifier )
{
QString quoted = identifier;
quoted.replace( '"', "\"\"" );
quoted = quoted.prepend( '\"' ).append( '\"' );
return quoted;
}

QString QgsSqlExpressionCompiler::quotedValue( const QVariant& value )
{
if ( value.isNull() )
return "NULL";

switch ( value.type() )
{
case QVariant::Int:
case QVariant::LongLong:
case QVariant::Double:
return value.toString();

case QVariant::Bool:
return value.toBool() ? "TRUE" : "FALSE";

default:
case QVariant::String:
QString v = value.toString();
v.replace( '\'', "''" );
if ( v.contains( '\\' ) )
return v.replace( '\\', "\\\\" ).prepend( "E'" ).append( '\'' );
else
return v.prepend( '\'' ).append( '\'' );
}
}

QgsSqlExpressionCompiler::Result QgsSqlExpressionCompiler::compile( const QgsExpression::Node* node, QString& result )
{
switch ( node->nodeType() )
{
case QgsExpression::ntUnaryOperator:
{
const QgsExpression::NodeUnaryOperator* n = static_cast<const QgsExpression::NodeUnaryOperator*>( node );
switch ( n->op() )
{
case QgsExpression::uoNot:
break;

case QgsExpression::uoMinus:
break;
}

break;
}

case QgsExpression::ntBinaryOperator:
{
const QgsExpression::NodeBinaryOperator* n = static_cast<const QgsExpression::NodeBinaryOperator*>( node );

QString op;
bool partialCompilation = false;
switch ( n->op() )
{
case QgsExpression::boEQ:
if ( mFlags.testFlag( CaseInsensitiveStringMatch ) && n->opLeft()->nodeType() == QgsExpression::ntColumnRef && n->opRight()->nodeType() == QgsExpression::ntColumnRef )
{
// equality between column refs results in a partial compilation, since provider is performing
// case-insensitive matches between strings
partialCompilation = true;
}

op = "=";
break;

case QgsExpression::boGE:
op = ">=";
break;

case QgsExpression::boGT:
op = ">";
break;

case QgsExpression::boLE:
op = "<=";
break;

case QgsExpression::boLT:
op = "<";
break;

case QgsExpression::boIs:
op = "IS";
break;

case QgsExpression::boIsNot:
op = "IS NOT";
break;

case QgsExpression::boLike:
op = "LIKE";
break;

case QgsExpression::boILike:
op = "ILIKE";
break;

case QgsExpression::boNotLike:
op = "NOT LIKE";
break;

case QgsExpression::boNotILike:
op = "NOT ILIKE";
break;

case QgsExpression::boOr:
op = "OR";
break;

case QgsExpression::boAnd:
op = "AND";
break;

case QgsExpression::boNE:
op = "<>";
break;

case QgsExpression::boMul:
op = "*";
break;

case QgsExpression::boPlus:
op = "+";
break;

case QgsExpression::boMinus:
op = "-";
break;

case QgsExpression::boDiv:
return Fail; // handle cast to real

case QgsExpression::boMod:
op = "%";
break;

case QgsExpression::boConcat:
op = "||";
break;

case QgsExpression::boIntDiv:
return Fail; // handle cast to int

case QgsExpression::boPow:
op = "^";
break;

case QgsExpression::boRegexp:
op = "~";
break;
}

if ( op.isNull() )
return Fail;

QString left;
Result lr( compile( n->opLeft(), left ) );

QString right;
Result rr( compile( n->opRight(), right ) );

result = left + ' ' + op + ' ' + right;
if ( lr == Complete && rr == Complete )
return ( partialCompilation ? Partial : Complete );
else if (( lr == Partial && rr == Complete ) || ( lr == Complete && rr == Partial ) || ( lr == Partial && rr == Partial ) )
return Partial;
else
return Fail;
}

case QgsExpression::ntLiteral:
{
const QgsExpression::NodeLiteral* n = static_cast<const QgsExpression::NodeLiteral*>( node );
if ( mFlags.testFlag( CaseInsensitiveStringMatch ) && n->value().type() == QVariant::String )
{
// provider uses case insensitive matching, so if literal was a string then we only have a Partial compilation and need to
// double check results using QGIS' expression engine
result = quotedValue( n->value() );
return Partial;
}
else
{
result = quotedValue( n->value() );
return Complete;
}
}

case QgsExpression::ntColumnRef:
{
const QgsExpression::NodeColumnRef* n = static_cast<const QgsExpression::NodeColumnRef*>( node );

if ( mFields.indexFromName( n->name() ) == -1 )
// Not a provider field
return Fail;

result = quotedIdentifier( n->name() );

return Complete;
}

case QgsExpression::ntInOperator:
{
const QgsExpression::NodeInOperator* n = static_cast<const QgsExpression::NodeInOperator*>( node );
QStringList list;

Result inResult = Complete;
Q_FOREACH ( const QgsExpression::Node* ln, n->list()->list() )
{
QString s;
Result r = compile( ln, s );
if ( r == Complete || r == Partial )
{
list << s;
if ( r == Partial )
inResult = Partial;
}
else
return r;
}

QString nd;
Result rn = compile( n->node(), nd );
if ( rn != Complete && rn != Partial )
return rn;

result = QString( "%1 %2IN(%3)" ).arg( nd, n->isNotIn() ? "NOT " : "", list.join( "," ) );
return ( inResult == Partial || rn == Partial ) ? Partial : Complete;
}

case QgsExpression::ntFunction:
case QgsExpression::ntCondition:
break;
}

return Fail;
}
102 changes: 102 additions & 0 deletions src/core/qgssqlexpressioncompiler.h
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/***************************************************************************
qgssqlexpressioncompiler.h
--------------------------
begin : November 2015
copyright : (C) 2015 Nyall Dawson
email : nyall dot dawson at gmail dot com
***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************/

#ifndef QGSSQLEXPRESSIONCOMPILER_H
#define QGSSQLEXPRESSIONCOMPILER_H

#include "qgsexpression.h"
#include "qgsfield.h"

/** \ingroup core
* \class QgsSqlExpressionCompiler
* \brief Generic expression compiler for translation to provider specific SQL WHERE clauses.
*
* This class is designed to be overriden 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
* \note Not part of stable API, may change in future versions of QGIS
* \note Not available in Python bindings
*/

class CORE_EXPORT QgsSqlExpressionCompiler
{
public:

/** Possible results from expression compilation */
enum Result
{
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 */
};

/** Enumeration of flags for how provider handles SQL clauses
*/
enum Flag
{
CaseInsensitiveStringMatch = 0x01, //!< Provider performs case-insensitive string matching
};
Q_DECLARE_FLAGS( Flags, Flag )

/** Constructor for expression compiler.
* @param fields fields from provider
* @param flags flags which control how expression is compiled
*/
explicit QgsSqlExpressionCompiler( const QgsFields& fields, const Flags& flags = ( Flags )0 );
virtual ~QgsSqlExpressionCompiler();

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

/** Returns the compiled expression string for use by the provider.
*/
virtual QString result() { return mResult; }

protected:

/** 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 quotedValue()
*/
virtual QString quotedIdentifier( const QString& identifier );

/** 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.
* @see quotedIdentifier()
*/
virtual QString quotedValue( const QVariant& value );

/** Compiles an expression node and returns the result of the compilation.
* @param node expression node to compile
* @param str string representing compiled node should be stored in this parameter
* @returns result of node compilation
*/
virtual Result compile( const QgsExpression::Node* node, QString& str );

QString mResult;
QgsFields mFields;

private:

Flags mFlags;

};

Q_DECLARE_OPERATORS_FOR_FLAGS( QgsSqlExpressionCompiler::Flags )

#endif // QGSSQLEXPRESSIONCOMPILER_H

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