Package com.mckoi.database.interpret

Class TableExpressionFromSet

  • class TableExpressionFromSet
extends java.lang.Object
    A set of tables and function references that make up the resources made available by a table expression. When a SelectQueriable is prepared this object is created and is used to dereference names to sources. It also has the ability to chain to another TableExpressionFromSet and resolve references over a complex sub-query hierarchy.

    • Field Detail

      • table_resources

        private java.util.ArrayList table_resources
        The list of table resources in this set. (FromTableInterface).

      • function_resources

        private java.util.ArrayList function_resources
        The list of function expression resources. For example, one table expression may expose a function as 'SELECT (a + b) AS c, ....' in which case we have a virtual assignment of c = (a + b) in this set.

      • exposed_variables

        private java.util.ArrayList exposed_variables
        The list of Variable references in this set that are exposed to the outside, including function aliases. For example, SELECT a, b, c, (a + 1) d FROM ABCTable Would be exposing variables 'a', 'b', 'c' and 'd'.

      • case_insensitive

        private boolean case_insensitive
        Set to true if this should do case insensitive resolutions.

      • parent

        private TableExpressionFromSet parent
        The parent TableExpressionFromSet if one exists. This is used for chaining a set of table sets together. When chained the 'globalResolveVariable' method can be used to resolve a reference in the chain.

    • Constructor Detail

      • TableExpressionFromSet

        public TableExpressionFromSet​(DatabaseConnection connection)
        Constructs the object.

    • Method Detail

      • setParent

        public void setParent​(TableExpressionFromSet parent)
        Sets the parent of this expression. parent can be set to null.

      • getParent

        public TableExpressionFromSet getParent()
        Returns the parent of this set. If it has no parent it returns null.

      • setCaseInsensitive

        public void setCaseInsensitive​(boolean status)
        Toggle the case sensitivity flag.

      • stringCompare

        boolean stringCompare​(java.lang.String str1,
                      java.lang.String str2)

      • addTable

        public void addTable​(FromTableInterface table_resource)
        Adds a table resource to the set.

      • addFunctionRef

        public void addFunctionRef​(java.lang.String name,
                           Expression expression)
        Adds a function resource to the set. Note that is possible for there to be references in the 'expression' that do not reference resources in this set. For example, a correlated reference.

      • exposeVariable

        public void exposeVariable​(Variable v)
        Adds a variable in this from set that is exposed to the outside. This list should contain all references from the SELECT ... part of the query. For example, SELECT a, b, (a + 1) d exposes variables a, b and d.

      • exposeAllColumnsFromSource

        public void exposeAllColumnsFromSource​(FromTableInterface table)
        Exposes all the columns from the given FromTableInterface.

      • exposeAllColumns

        public void exposeAllColumns()
        Exposes all the columns in all the child tables.

      • exposeAllColumnsFromSource

        public void exposeAllColumnsFromSource​(TableName tn)
        Exposes all the columns from the given table name.

      • generateResolvedVariableList

        public Variable[] generateResolvedVariableList()
        Returns a Variable[] array for each variable that is exposed in this from set. This is a list of fully qualified variables that are referencable from the final result of the table expression.

      • findTable

        FromTableInterface findTable​(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.

      • setCount

        int setCount()
        Returns the number of FromTableInterface objects in this set.

      • getTable

        FromTableInterface getTable​(int i)
        Returns the FromTableInterface object at the given index position in this set.

      • dereferenceAssignment

        Expression dereferenceAssignment​(Variable v)
        Dereferences a fully qualified reference that is within this set. For example, SELECT ( a + b ) AS z given 'z' would return the expression (a + b).

        Returns null if unable to dereference assignment because it does not exist.

      • resolveAssignmentReference

        private Variable resolveAssignmentReference​(Variable v)
        Resolves the given Variable object to an assignment if it's possible to do so within the context of this set. If the variable can not be unambiguously resolved to a function or aliased column, a StatementException is thrown. If the variable isn't assigned to any function or aliased column, 'null' is returned.

      • resolveTableColumnReference

        Variable resolveTableColumnReference​(Variable v)
        Resolves the given Variable against the table columns in this from set. If the variable does not resolve to anything 'null' is returned. If the variable is ambiguous, a StatementException is thrown.

        Note that the given variable does not have to be fully qualified but the returned expressions are fully qualified.

      • resolveReference

        Variable resolveReference​(Variable v)
        Resolves the given Variable object to a fully resolved Variable within the context of this table expression. If the variable does not resolve to anything 'null' is returned. If the variable is ambiguous, a StatementException is thrown.

        If the variable name references a table column, an expression with a single Variable element is returned. If the variable name references a function, an expression of the function is returned.

        Note that the given variable does not have to be fully qualified but the returned expressions are fully qualified.

      • globalResolveReference

        CorrelatedVariable globalResolveReference​(int level,
                                          Variable v)
        Resolves the given Variable reference within the chained list of TableExpressionFromSet objects to a CorrelatedVariable. If the reference is not found in this set the method recurses to the parent set. The first unambiguous reference is returned.

        If resolution is ambiguous within a set, a StatementException is thrown.

        Returns null if the reference could not be resolved.

      • qualifyVariable

        java.lang.Object qualifyVariable​(Variable v_in)
        Attempts to qualify the given Variable object to a value found either in this from set, or a value in the parent from set. A variable that is qualified by the parent is called a correlated variable. Any correlated variables that are successfully qualified are returned as CorrelatedVariable objects.

      • expressionQualifier

        ExpressionPreparer expressionQualifier()
        Returns an ExpressionPreparer that qualifies all variables in an expression to either a qualified Variable or a CorrelatedVariable object.