SetNullReferencedExecuter


1   package com.daffodilwoods.daffodildb.server.serversystem.dmlvalidation.constraintsystem;
2   
3   import com.daffodilwoods.daffodildb.server.datadictionarysystem.*;
4   import com.daffodilwoods.daffodildb.server.datasystem.utility.*;
5   import com.daffodilwoods.daffodildb.server.serversystem.*;
6   import com.daffodilwoods.daffodildb.server.sessionsystem.sessioncondition.*;
7   import com.daffodilwoods.daffodildb.server.sql99.dql.iterator.*;
8   import com.daffodilwoods.daffodildb.server.sql99.expression.booleanvalueexpression.*;
9   import com.daffodilwoods.database.general.*;
10  import com.daffodilwoods.database.resource.*;
11  
12  /**
13   * Objective of the class is to set the referenced column values to NULL in the child
14   * table when parent table is specified with foreign constraint if the delete
15   * rule or update rule is specified with option SET NULL for any match option.
16   */
17  
18  public class SetNullReferencedExecuter extends ReferencedExecuter {
19  
20    /**
21     * Constructor : used to construct a new instance of foreign constraint with
22     * the given arguments.
23     * @param referencedConstraint Value of the Referenced Constraint Descriptor
24     * having the details of the referenced constraints
25     * @param globalSess instance of _ServerSession
26     * @param dd
27     * @throws DException
28     */
29    public SetNullReferencedExecuter( _ReferentialConstraint referencedConstraint, _ServerSession globalSess ) throws DException {
30      globalSession = globalSess;
31      setVariables( referencedConstraint );
32    }
33  
34    /**
35     * The following method fires all the constraints which having delete/update rule
36     * with action set to SET NULL. A private method is further called to
37     * set the matching column values as null in referencing table.
38     * values.
39     */
40    public void checkReferencedConstraints( _StatementExecutionContext sec ) throws DException {
41      populateMatchingIterator();
42      for( int i=0; i< matchingRowsPool.size(); i++ )
43          matching_SETNULL( i , sec );
44    }
45  
46    /**
47     * The following method updates matched rows got from the iterator on child table with
48     * conditional columns as the referencing columns values from the child table
49     * and values equal to NULL.
50     */
51    private void matching_SETNULL( int tableIndex, _StatementExecutionContext statementExecutionContext ) throws DException {
52        ConstraintStore constraintStore = (ConstraintStore)matchingRowsPool.get(tableIndex);
53        RecordVersion recordVersion  = statementExecutionContext.getRecordVersion();
54        _Iterator iterator          = constraintStore.getIterator();
55        booleanvalueexpression bve  = constraintStore.getCondition();
56        setParameterValues( iterator , bve , recordVersion.getPreviousRecord() );
57        if(iterator.last()){
58            _ServerTable serverTable = statementExecutionContext.getServerTable( (QualifiedIdentifier)sub_superTable.get(tableIndex) );
59            do {
60                int[] column = new int[ referencingColumns.length ];
61                Object  [] values = new Object  [ referencingColumns.length ];
62                for( int i=0; i<referencingColumns.length; i++ ) {
63                    column[i] = referencingColumns[i];
64                    values[i] = null ;
65                }
66  
67                serverTable.update( iterator , column , values , statementExecutionContext );
68            }while( iterator.previous() ) ;
69        }
70    }
71  
72  }
73
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