Class ExpressionClassBuilder

java.lang.Object
org.apache.derby.impl.sql.compile.ExpressionClassBuilder
All Implemented Interfaces:
ExpressionClassBuilderInterface
Direct Known Subclasses:
ActivationClassBuilder

abstract class ExpressionClassBuilder extends Object implements ExpressionClassBuilderInterface
ExpressionClassBuilder provides an interface to satisfy generation's common tasks in building classes that involve expressions. This is the common superclass of ActivationClassBuilder and FilterClassBuilder. See the documentation on ActivationClassBuilder.
  • Field Details

    • currentDatetimeFieldName

      protected static final String currentDatetimeFieldName
      See Also:
    • cb

      protected ClassBuilder cb
    • gc

      protected GeneratedClass gc
    • nextExprNum

      protected int nextExprNum
    • nextNonFastExpr

      protected int nextNonFastExpr
    • nextFieldNum

      protected int nextFieldNum
    • constructor

      protected MethodBuilder constructor
    • myCompCtx

      CompilerContext myCompCtx
    • executeMethod

      MethodBuilder executeMethod
    • cdtField

      protected LocalField cdtField
    • currentRowScanResultSetName

      private String currentRowScanResultSetName
    • getDVF

      private Object getDVF
      Get/reuse the Expression for getting the DataValueFactory
    • getRSF

      private Object getRSF
      This is a utility method to get a common expression -- "BaseActivation.getResultSetFactory()".

      BaseActivation gets the factory from the context and caches it for faster retrieval.

    • getEF

      private Object getEF
      This is a utility method to get a common expression -- "BaseActivation.getExecutionFactory()". REVISIT: could the same expression objects be reused within the tree and have the correct java generated each time?

      BaseActivation gets the factory from the context and caches it for faster retrieval.

  • Constructor Details

    • ExpressionClassBuilder

      ExpressionClassBuilder(String superClass, String className, CompilerContext cc) throws StandardException
      By the time this is done, it has constructed the following class:
          final public class #className extends #superClass {
            public #className() { super(); }
          }
       
      Throws:
      StandardException - thrown on failure
  • Method Details

    • getPackageName

      abstract String getPackageName()
      Get the name of the package that the generated class will live in.
      Returns:
      name of package that the generated class will live in.
    • getRowCount

      abstract int getRowCount() throws StandardException
      Get the number of ExecRows that must be allocated
      Returns:
      number of ExecRows that must be allocated
      Throws:
      StandardException - thrown on failure
    • setNumSubqueries

      abstract void setNumSubqueries() throws StandardException
      Sets the number of subqueries under this expression
      Throws:
      StandardException - thrown on failure
    • getBaseClassName

      abstract String getBaseClassName()
      Return the base class of the activation's hierarchy (the subclass of Object). This class is expected to hold methods used by all compilation code, such as datatype compilation code, e.g. getDataValueFactory.
    • getConstructor

      MethodBuilder getConstructor()
    • getClassBuilder

      ClassBuilder getClassBuilder()
    • getExecuteMethod

      MethodBuilder getExecuteMethod()
      Get a method builder for adding code to the execute() method. The method builder does not actually build a method called execute. Instead, it creates a method that overrides the reinit() method, which is called from execute() on every execution in order to reinitialize the data structures.
    • beginConstructor

      private void beginConstructor()
    • finishConstructor

      void finishConstructor() throws StandardException
      Finish the constructor by newing the array of Rows and putting a return at the end of it.
      Throws:
      StandardException - thrown on failure
    • addNewArrayOfRows

      private void addNewArrayOfRows(int numResultSets)
      Generate the assignment for row = new ExecRow[numResultSets]
      Parameters:
      numResultSets - The size of the array.
    • newFieldDeclaration

      LocalField newFieldDeclaration(int modifiers, String type, String name)
      Add a field declaration to the generated class
      Parameters:
      modifiers - The | of the modifier values such as public, static, etc.
      type - The type of the field in java language.
      name - The name of the field.
      Returns:
      None.
    • newFieldDeclaration

      LocalField newFieldDeclaration(int modifiers, String type)
      Add an arbitrarily named field to the generated class. This is used to generate fields where the caller doesn't care what the field is named. It is especially useful for generating arbitrary numbers of fields, where the caller doesn't know in advance how many fields will be used. For example, it is used for generating fields to hold intermediate values from expressions.
      Parameters:
      modifiers - The | of the modifier values such as public, static, etc.
      type - The type of the field in java language.
      Returns:
      The name of the new field
    • newGeneratedFun

      MethodBuilder newGeneratedFun(String returnType, int modifiers)
      Activations might have need of internal functions that are not used by the result sets, but by other activation functions. Thus, we make it possible for functions to be generated directly as well as through the newExprFun interface. newExprFun should be used when a static field pointing to the expression function is needed.

      The generated function will generally have a generated name that can be viewed through the MethodBuilder interface. This name is generated to ensure uniqueness from other function names in the activation class. If you pass in a function name, think carefully about whether it will collide with other names.

      Parameters:
      returnType - the return type of the function
      modifiers - the modifiers on the function
      See Also:
    • newGeneratedFun

      MethodBuilder newGeneratedFun(String returnType, int modifiers, String[] params)
    • newGeneratedFun

      private MethodBuilder newGeneratedFun(String exprName, String returnType, int modifiers, String[] params)
    • newExprFun

      MethodBuilder newExprFun()
      "ExprFun"s are the "expression functions" that are specific to a given JSQL statement. For example, an ExprFun is generated to evaluate the where clause of a select statement and return a boolean result.

      All methods return by this are expected to be called via the GeneratedMethod interface. Thus the methods are public and return java.lang.Object.

      Once the exprfun has been created, the caller will need to add statements to it, minimally a return statement.

      ExprFuns return Object types, since they are invoked through reflection and thus their return type would get wrapped in an object anyway. For example: return java.lang.Boolean, not boolean.

    • pushMethodReference

      void pushMethodReference(MethodBuilder mb, MethodBuilder exprMethod)
      Push an expression that is a GeneratedMethod reference to the passed in method. aka. a "function pointer".
    • newUserExprFun

      MethodBuilder newUserExprFun()
      Start a user expression. The difference between a normal expression (returned by newExprFun) and a user expression is that a user expression catches all exceptions (because we don't want random exceptions thrown from user methods to propagate to the rest of the system.
      Returns:
      A new MethodBuilder
    • getCurrentDateExpression

      void getCurrentDateExpression(MethodBuilder mb)
      This utility method returns an expression for CURRENT_DATE. Get the expression this way, because the activation needs to generate support information for CURRENT_DATE, that would otherwise be painful to create manually.
    • getCurrentTimeExpression

      void getCurrentTimeExpression(MethodBuilder mb)
      This utility method returns an expression for CURRENT_TIME. Get the expression this way, because the activation needs to generate support information for CURRENT_TIME, that would otherwise be painful to create manually.
    • getCurrentTimestampExpression

      void getCurrentTimestampExpression(MethodBuilder mb)
      This utility method generates an expression for CURRENT_TIMESTAMP. Get the expression this way, because the activation needs to generate support information for CURRENT_TIMESTAMP, that would otherwise be painful to create manually.
    • getColumnOrdering

      FormatableArrayHolder getColumnOrdering(ResultColumnList rclist)
      These utility methods buffers compilation from the IndexColumnOrder class. They create an ordering based on their parameter, stuff that into the prepared statement, and then return the entry # for use in the generated code. We could write another utility method to generate code to turn an entry # back into an object, but so far no-one needs it. WARNING: this is a crafty method that ASSUMES that you want every column in the list ordered, and that every column in the list is the entire actual result colunm. It is only useful for DISTINCT in select.
    • addColumnToOrdering

      FormatableArrayHolder addColumnToOrdering(FormatableArrayHolder orderingHolder, int columnNum)
      Add a column to the existing Ordering list. Takes a column id and only adds it if it isn't in the list.
      Returns:
      the ColumnOrdering array
    • getColumnOrdering

      FormatableArrayHolder getColumnOrdering(OrderedColumnList<?> oclist)
    • addItem

      int addItem(Object o)
    • pushDataValueFactory

      void pushDataValueFactory(MethodBuilder mb)
    • pushGetResultSetFactoryExpression

      void pushGetResultSetFactoryExpression(MethodBuilder mb)
    • pushGetExecutionFactoryExpression

      void pushGetExecutionFactoryExpression(MethodBuilder mb)
    • pushColumnReference

      void pushColumnReference(MethodBuilder mb, int rsNumber, int colId)
      Generate a reference to a colunm in a result set.
      Parameters:
      rsNumber - the result set number
      colId - the column number
    • pushPVSReference

      void pushPVSReference(MethodBuilder mb)
      Generate a reference to the parameter value set that all activations use.
    • getCurrentSetup

      protected LocalField getCurrentSetup()
    • newFieldName

      private String newFieldName()
      generated the next field name available. these are of the form 'e#', where # is incremented each time. This shares the name space with the expression methods as Java allows names and fields to have the same name. This reduces the number of constant pool entries created for a generated class file.
    • getTypeCompiler

      protected TypeCompiler getTypeCompiler(TypeId typeId)
      Get the TypeCompiler associated with the given TypeId
      Parameters:
      typeId - The TypeId to get a TypeCompiler for
      Returns:
      The corresponding TypeCompiler
    • getGeneratedClass

      GeneratedClass getGeneratedClass(ByteArray savedBytes) throws StandardException
      Take the generated class, and turn it into an actual class.

      This method assumes, does not check, that the class and its parts are all complete.

      Parameters:
      savedBytes - place to save generated bytes. if null, it is ignored
      Throws:
      StandardException - thrown when exception occurs
    • pushThisAsActivation

      void pushThisAsActivation(MethodBuilder mb)
      Get a "this" expression declared as an Activation. This is the commonly used type of the this expression.
    • generateNull

      void generateNull(MethodBuilder mb, TypeCompiler tc, int collationType)
      Generate a Null data value. Nothing is required on the stack, a SQL null data value is pushed.
    • generateNullWithExpress

      void generateNullWithExpress(MethodBuilder mb, TypeCompiler tc, int collationType)
      Generate a Null data value. The express value is required on the stack and will be popped, a SQL null data value is pushed.
    • generateDataValue

      void generateDataValue(MethodBuilder mb, TypeCompiler tc, int collationType, LocalField field)
      Generate a data value. The value is to be set in the SQL data value is required on the stack and will be popped, a SQL data value is pushed.
    • newRowLocationScanResultSetName

      String newRowLocationScanResultSetName()
      generates a variable name for the rowscanresultset. This can not be a fixed name because in cases like cascade delete same activation class will be dealing more than one RowScanResultSets for dependent tables.
    • getRowLocationScanResultSetName

      String getRowLocationScanResultSetName()