QGIS API Documentation
3.4.15-Madeira (e83d02e274)
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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... | |
bool | opIsStringComparison (QgsExpressionNodeBinaryOperator::BinaryOperator op) |
Returns true if op is one of. 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 QString | castToText (const QString &value) const |
Casts a value to a text 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 |
Returns the Arguments for SQL function for the expression function. More... | |
virtual QString | sqlFunctionFromFunctionName (const QString &fnName) const |
Returns the SQL function for the expression function. More... | |
Protected Attributes | |
QgsFields | mFields |
QString | mResult |
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.
Definition at line 40 of file qgssqlexpressioncompiler.h.
Enumeration of flags for how provider handles SQL clauses.
Enumerator | |
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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 56 of file qgssqlexpressioncompiler.h.
Possible results from expression compilation.
Definition at line 45 of file qgssqlexpressioncompiler.h.
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explicit |
Constructor for expression compiler.
fields | fields from provider |
flags | flags which control how expression is compiled |
Definition at line 21 of file qgssqlexpressioncompiler.cpp.
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virtualdefault |
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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.
Definition at line 432 of file qgssqlexpressioncompiler.cpp.
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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.
Definition at line 421 of file qgssqlexpressioncompiler.cpp.
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protectedvirtual |
Casts a value to a text result.
Subclasses that support casting to text may implement this function to get equal behavior to the QGIS expression engine when string comparison operators are applied on non-string data.
Example:
579 LIKE '5%'
which on a postgres database needs to be
579::text LIKE '5%'
Definition at line 427 of file qgssqlexpressioncompiler.cpp.
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virtual |
Compiles an expression and returns the result of the compilation.
Definition at line 28 of file qgssqlexpressioncompiler.cpp.
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protectedvirtual |
Compiles an expression node and returns the result of the compilation.
node | expression node to compile |
str | string representing compiled node should be stored in this parameter |
Definition at line 89 of file qgssqlexpressioncompiler.cpp.
bool QgsSqlExpressionCompiler::opIsStringComparison | ( | QgsExpressionNodeBinaryOperator::BinaryOperator | op | ) |
Returns true if op is one of.
In such cases the left operator will be cast to string to behave equal to QGIS own expression engine.
Definition at line 41 of file qgssqlexpressioncompiler.cpp.
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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.
Definition at line 53 of file qgssqlexpressioncompiler.cpp.
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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.
value | value to quote |
ok | wil be set to true if value can be compiled |
Definition at line 61 of file qgssqlexpressioncompiler.cpp.
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virtual |
Returns the compiled expression string for use by the provider.
Definition at line 36 of file qgssqlexpressioncompiler.cpp.
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protectedvirtual |
Returns the Arguments for SQL function for the expression function.
Derived classes should override this to help compile functions
fnName | expression function name |
fnArgs | arguments from expression |
Definition at line 415 of file qgssqlexpressioncompiler.cpp.
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protectedvirtual |
Returns the SQL function for the expression function.
Derived classes should override this to help compile functions
fnName | expression function name |
Definition at line 409 of file qgssqlexpressioncompiler.cpp.
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protected |
Definition at line 177 of file qgssqlexpressioncompiler.h.
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protected |
Definition at line 176 of file qgssqlexpressioncompiler.h.