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       1                 :            : /***************************************************************************
       2                 :            :                              qgssqlexpressioncompiler.h
       3                 :            :                              --------------------------
       4                 :            :     begin                : November 2015
       5                 :            :     copyright            : (C) 2015 Nyall Dawson
       6                 :            :     email                : nyall dot dawson at gmail dot com
       7                 :            :  ***************************************************************************
       8                 :            :  *                                                                         *
       9                 :            :  *   This program is free software; you can redistribute it and/or modify  *
      10                 :            :  *   it under the terms of the GNU General Public License as published by  *
      11                 :            :  *   the Free Software Foundation; either version 2 of the License, or     *
      12                 :            :  *   (at your option) any later version.                                   *
      13                 :            :  *                                                                         *
      14                 :            :  ***************************************************************************/
      15                 :            : 
      16                 :            : #ifndef QGSSQLEXPRESSIONCOMPILER_H
      17                 :            : #define QGSSQLEXPRESSIONCOMPILER_H
      18                 :            : 
      19                 :            : #define SIP_NO_FILE
      20                 :            : 
      21                 :            : #include "qgis_core.h"
      22                 :            : #include "qgsfields.h"
      23                 :            : #include "qgsexpressionnodeimpl.h"
      24                 :            : 
      25                 :            : class QgsExpression;
      26                 :            : class QgsExpressionNode;
      27                 :            : 
      28                 :            : /**
      29                 :            :  * \ingroup core
      30                 :            :  * \class QgsSqlExpressionCompiler
      31                 :            :  * \brief Generic expression compiler for translation to provider specific SQL WHERE clauses.
      32                 :            :  *
      33                 :            :  * This class is designed to be overridden by providers to take advantage of expression compilation,
      34                 :            :  * so that feature requests can take advantage of the provider's native filtering support.
      35                 :            :  * \note Not part of stable API, may change in future versions of QGIS
      36                 :            :  * \note Not available in Python bindings
      37                 :            :  * \since QGIS 2.14
      38                 :            :  */
      39                 :            : 
      40                 :            : class CORE_EXPORT QgsSqlExpressionCompiler
      41                 :            : {
      42                 :            :   public:
      43                 :            : 
      44                 :            :     //! Possible results from expression compilation
      45                 :            :     enum Result
      46                 :            :     {
      47                 :            :       None, //!< No expression
      48                 :            :       Complete, //!< Expression was successfully compiled and can be completely delegated to provider
      49                 :            :       Partial, //!< Expression was partially compiled, but provider will return extra records and results must be double-checked using QGIS' expression engine
      50                 :            :       Fail //!< Provider cannot handle expression
      51                 :            :     };
      52                 :            : 
      53                 :            :     /**
      54                 :            :      * Enumeration of flags for how provider handles SQL clauses
      55                 :            :      */
      56                 :            :     enum Flag
      57                 :            :     {
      58                 :            :       CaseInsensitiveStringMatch = 1,  //!< Provider performs case-insensitive string matching for all strings
      59                 :            :       LikeIsCaseInsensitive = 1 << 1, //!< Provider treats LIKE as case-insensitive
      60                 :            :       NoNullInBooleanLogic = 1 << 2, //!< Provider does not support using NULL with boolean logic, e.g., "(...) OR NULL"
      61                 :            :       NoUnaryMinus = 1 << 3, //!< Provider does not unary minus, e.g., " -( 100 * 2 ) = ..."
      62                 :            :       IntegerDivisionResultsInInteger = 1 << 4, //!< Dividing int by int results in int on provider. Subclass must implement the castToReal() function to allow compilation of division.
      63                 :            :     };
      64                 :            :     Q_DECLARE_FLAGS( Flags, Flag )
      65                 :            : 
      66                 :            :     /**
      67                 :            :      * Constructor for expression compiler.
      68                 :            :      * \param fields fields from provider
      69                 :            :      * \param flags flags which control how expression is compiled
      70                 :            :      * \param ignoreStaticNodes If an expression has been partially precalculated due to static nodes in the expression, setting this argument to FALSE
      71                 :            :      * will prevent these precalculated values from being utilized during compilation of the expression. This flag significantly limits the effectiveness
      72                 :            :      * of compilation and should be used for debugging purposes only. (Since QGIS 3.18)
      73                 :            :      */
      74                 :            :     explicit QgsSqlExpressionCompiler( const QgsFields &fields, QgsSqlExpressionCompiler::Flags flags = Flags(), bool ignoreStaticNodes = false );
      75                 :          0 :     virtual ~QgsSqlExpressionCompiler() = default;
      76                 :            : 
      77                 :            :     /**
      78                 :            :      * Compiles an expression and returns the result of the compilation.
      79                 :            :      */
      80                 :            :     virtual Result compile( const QgsExpression *exp );
      81                 :            : 
      82                 :            :     /**
      83                 :            :      * Returns the compiled expression string for use by the provider.
      84                 :            :      */
      85                 :            :     virtual QString result();
      86                 :            : 
      87                 :            :     /**
      88                 :            :      * Returns TRUE if \a op is one of
      89                 :            :      *
      90                 :            :      * - LIKE
      91                 :            :      * - ILIKE
      92                 :            :      * - NOT LIKE
      93                 :            :      * - NOT ILIKE
      94                 :            :      * - ~ (regexp)
      95                 :            :      *
      96                 :            :      * In such cases the left operator will be cast to string to behave equal to
      97                 :            :      * QGIS own expression engine.
      98                 :            :      *
      99                 :            :      * \since QGIS 3.2
     100                 :            :      */
     101                 :            :     bool opIsStringComparison( QgsExpressionNodeBinaryOperator::BinaryOperator op );
     102                 :            : 
     103                 :            :   protected:
     104                 :            : 
     105                 :            :     /**
     106                 :            :      * Returns a quoted column identifier, in the format expected by the provider.
     107                 :            :      * Derived classes should override this if special handling of column identifiers
     108                 :            :      * is required.
     109                 :            :      * \see quotedValue()
     110                 :            :      */
     111                 :            :     virtual QString quotedIdentifier( const QString &identifier );
     112                 :            : 
     113                 :            :     /**
     114                 :            :      * Returns a quoted attribute value, in the format expected by the provider.
     115                 :            :      * Derived classes should override this if special handling of attribute values is required.
     116                 :            :      * \param value value to quote
     117                 :            :      * \param ok will be set to TRUE if value can be compiled
     118                 :            :      * \see quotedIdentifier()
     119                 :            :      */
     120                 :            :     virtual QString quotedValue( const QVariant &value, bool &ok );
     121                 :            : 
     122                 :            :     /**
     123                 :            :      * Compiles an expression node and returns the result of the compilation.
     124                 :            :      * \param node expression node to compile
     125                 :            :      * \param str string representing compiled node should be stored in this parameter
     126                 :            :      * \returns result of node compilation
     127                 :            :      */
     128                 :            :     virtual Result compileNode( const QgsExpressionNode *node, QString &str );
     129                 :            : 
     130                 :            :     /**
     131                 :            :      * Returns the SQL function for the expression function.
     132                 :            :      * Derived classes should override this to help compile functions
     133                 :            :      * \param fnName expression function name
     134                 :            :      * \returns the SQL function name
     135                 :            :      */
     136                 :            :     virtual QString sqlFunctionFromFunctionName( const QString &fnName ) const;
     137                 :            : 
     138                 :            :     /**
     139                 :            :      * Returns the Arguments for SQL function for the expression function.
     140                 :            :      * Derived classes should override this to help compile functions
     141                 :            :      * \param fnName expression function name
     142                 :            :      * \param fnArgs arguments from expression
     143                 :            :      * \returns the arguments updated for SQL Function
     144                 :            :      */
     145                 :            :     virtual QStringList sqlArgumentsFromFunctionName( const QString &fnName, const QStringList &fnArgs ) const;
     146                 :            : 
     147                 :            :     /**
     148                 :            :      * Casts a value to a real result. Subclasses which indicate the IntegerDivisionResultsInInteger
     149                 :            :      * flag must reimplement this to cast a numeric value to a real type value so that division results
     150                 :            :      * in a real value result instead of integer.
     151                 :            :      * \since QGIS 3.0
     152                 :            :      */
     153                 :            :     virtual QString castToReal( const QString &value ) const;
     154                 :            : 
     155                 :            :     /**
     156                 :            :      * Casts a value to a text result. Subclasses that support casting to text may implement this function
     157                 :            :      * to get equal behavior to the QGIS expression engine when string comparison operators are applied
     158                 :            :      * on non-string data.
     159                 :            :      *
     160                 :            :      * ### Example
     161                 :            :      *
     162                 :            :      *     579 LIKE '5%'
     163                 :            :      *
     164                 :            :      * which on a postgres database needs to be
     165                 :            :      *
     166                 :            :      *     579::text LIKE '5%'
     167                 :            :      *
     168                 :            :      * \since QGIS 3.2
     169                 :            :      */
     170                 :            :     virtual QString castToText( const QString &value ) const;
     171                 :            : 
     172                 :            :     /**
     173                 :            :      * Casts a value to a integer result. Subclasses must reimplement this to cast a numeric value to a integer
     174                 :            :      * type value so that integer division results in a integer value result instead of real.
     175                 :            :      * \since QGIS 3.0
     176                 :            :      */
     177                 :            :     virtual QString castToInt( const QString &value ) const;
     178                 :            : 
     179                 :            :     /**
     180                 :            :      * Tries to replace a node by its static cached value where possible.
     181                 :            :      *
     182                 :            :      * \since QGIS 3.18
     183                 :            :      */
     184                 :            :     virtual Result replaceNodeByStaticCachedValueIfPossible( const QgsExpressionNode *node, QString &str );
     185                 :            : 
     186                 :            :     QString mResult;
     187                 :            :     QgsFields mFields;
     188                 :            : 
     189                 :            :   private:
     190                 :            : 
     191                 :            :     Flags mFlags;
     192                 :            : 
     193                 :            :     bool mIgnoreStaticNodes = false;
     194                 :            : 
     195                 :            :     bool nodeIsNullLiteral( const QgsExpressionNode *node ) const;
     196                 :            : 
     197                 :            : };
     198                 :            : 
     199                 :          0 : Q_DECLARE_OPERATORS_FOR_FLAGS( QgsSqlExpressionCompiler::Flags )
     200                 :            : 
     201                 :            : #endif // QGSSQLEXPRESSIONCOMPILER_H