Class Statement

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected StatementTree cmd
      The StatementTree object that is the container for the query.
      protected DatabaseConnection database
      The Database context.
      protected SQLQuery query
      The SQLQuery object that was used to produce this statement.
      protected java.util.Vector table_list
      The list of all FromTableInterface objects of resources referenced in this query.
      protected User user
      The user context.
    • Constructor Summary

      Constructors 
      Constructor Description
      Statement()  
    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      protected void addTable​(FromTableInterface table)
      Add an FromTableInterface that is used within this query.
      DebugLogger Debug()
      Returns a DebugLogger object used to log debug commands.
      abstract Table evaluate()
      Evaluates the statement and returns a table that represents the result set.
      (package private) boolean existsTableWithColumn​(Variable column_name)
      Given a fully resolved table name ( eg.
      (package private) FromTableInterface findTableInQuery​(java.lang.String schema, java.lang.String name)
      Returns the first FromTableInterface object that matches the given schema, table reference.
      (package private) FromTableInterface findTableWithColumn​(Variable column_name)
      Given a fully resolved table name ( eg.
      void init​(DatabaseConnection db, StatementTree stree, SQLQuery query)
      Sets up internal variables for this statement for derived classes to use.
      abstract void prepare()
      Prepares the statement with the given Database object.
      (package private) void reset()
      Resets this statement so it may be re-prepared and evaluated again.
      (package private) java.util.ArrayList resolveAgainstAliases​(Variable alias_name)
      Overwrite this method if your statement has some sort of column aliasing capability (such as a select statement).
      (package private) Variable resolveColumn​(Variable v)
      Attempts to resolve an ambiguous column name such as 'id' into a Variable from the tables in this statement.
      (package private) void resolveExpression​(Expression exp)
      Given an Expression, this will run through the expression and resolve any variable names via the 'resolveVariableName' method here.
      (package private) TableName resolveTableName​(java.lang.String name, DatabaseConnection db)
      Resolves a TableName string (eg.
      void resolveTree()
      Performs initial preparation on the contents of the StatementTree by resolving all sub queries and mapping functions to their executable forms.
      Variable resolveVariableName​(Variable v)
      Given a Variable object, this will resolve the name into a column name the database understands (substitutes aliases, etc).
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • user

        protected User user
        The user context.
      • cmd

        protected StatementTree cmd
        The StatementTree object that is the container for the query.
      • query

        protected SQLQuery query
        The SQLQuery object that was used to produce this statement.
      • table_list

        protected java.util.Vector table_list
        The list of all FromTableInterface objects of resources referenced in this query. (FromTableInterface)
    • Constructor Detail

      • Statement

        public Statement()
    • Method Detail

      • Debug

        public final DebugLogger Debug()
        Returns a DebugLogger object used to log debug commands.
      • reset

        void reset()
        Resets this statement so it may be re-prepared and evaluated again. Useful for repeating a query multiple times.
      • resolveTree

        public final void resolveTree()
                               throws DatabaseException
        Performs initial preparation on the contents of the StatementTree by resolving all sub queries and mapping functions to their executable forms.

        Given a StatementTree and a Database context, this method will convert all sub-queries found in the StatementTree to a Queriable object. In other words, all StatementTree are converted to Select objects. The given 'database' object is used as the session to prepare the sub-queries against.

        This is called after 'init' and before 'prepare'.

        Throws:
        DatabaseException
      • findTableWithColumn

        FromTableInterface findTableWithColumn​(Variable column_name)
        Given a fully resolved table name ( eg. Part.id ) this method will attempt to find the Table object that the column is in.
      • existsTableWithColumn

        boolean existsTableWithColumn​(Variable column_name)
        Given a fully resolved table name ( eg. Part.id ) this returns true if there is a table with the given column name, otherwise false.

        NOTE: Intended to be overwritten...

      • resolveAgainstAliases

        java.util.ArrayList resolveAgainstAliases​(Variable alias_name)
        Overwrite this method if your statement has some sort of column aliasing capability (such as a select statement). Returns a list of all fully qualified Variables that match the alias name, or an empty list if no matches found.

        By default, returns an empty list.

      • resolveTableName

        TableName resolveTableName​(java.lang.String name,
                                   DatabaseConnection db)
        Resolves a TableName string (eg. 'Customer' 'APP.Customer' ) to a TableName object. If the schema part of the table name is not present then it is set to the current schema of the database connection. If the database is ignoring the case then this will correctly resolve the table to the cased version of the table name.
      • findTableInQuery

        FromTableInterface findTableInQuery​(java.lang.String schema,
                                            java.lang.String name)
        Returns the first FromTableInterface object that matches the given schema, table reference. Returns null if no objects with the given schema/name reference match.
      • resolveColumn

        Variable resolveColumn​(Variable v)
        Attempts to resolve an ambiguous column name such as 'id' into a Variable from the tables in this statement.
      • resolveVariableName

        public Variable resolveVariableName​(Variable v)
        Given a Variable object, this will resolve the name into a column name the database understands (substitutes aliases, etc).
      • resolveExpression

        void resolveExpression​(Expression exp)
        Given an Expression, this will run through the expression and resolve any variable names via the 'resolveVariableName' method here.
      • addTable

        protected void addTable​(FromTableInterface table)
        Add an FromTableInterface that is used within this query. These tables are used when we try to resolve a column name.
      • init

        public final void init​(DatabaseConnection db,
                               StatementTree stree,
                               SQLQuery query)
        Sets up internal variables for this statement for derived classes to use. This is called before 'prepare' and 'isExclusive' is called.

        It is assumed that any ? style parameters in the StatementTree will have been resolved previous to a call to this method.

        Parameters:
        db - the DatabaseConnection that will execute this statement.
        stree - the StatementTree that contains the parsed content of the statement being executed.
      • prepare

        public abstract void prepare()
                              throws DatabaseException
        Prepares the statement with the given Database object. This is called before the statement is evaluated. The prepare statement queries the database and resolves information about the statement (for example, it resolves column names and aliases and determines the tables that are touched by this statement so we can lock the appropriate tables before we evaluate).

        NOTE: Care must be taken to ensure that all methods called here are safe in as far as modifications to the data occuring. The rules for safety should be as follows. If the database is in EXCLUSIVE mode, then we need to wait until it's switched back to SHARED mode before this method is called. All collection of information done here should not involve any table state info. except for column count, column names, column types, etc. Queries such as obtaining the row count, selectable scheme information, and certainly 'getCellContents' must never be called during prepare. When prepare finishes, the affected tables are locked and the query is safe to 'evaluate' at which time table state is safe to inspect.

        Throws:
        DatabaseException