Creating indexes

In this topic

• Creating an attribute index
• Deleting an index 
• Creating and rebuilding a spatial index

Creating an attribute index

• The Index class and the IIndexEdit interface are used to create an object, which specifies the properties of the index to be created.
• The IClass.AddIndex method (inherited by ITable and IFeatureClass) is used to actually create the index.

public void AddIndexToFeatureClass(IFeatureClass featureClass, String indexName,
    String nameOfField)
{
    // Ensure the feature class contains the specified field.
    int fieldIndex=featureClass.FindField(nameOfField);
    if (fieldIndex ==  - 1)
    {
        throw new ArgumentException(
            "The specified field does not exist in the feature class.");
    }

    // Get the specified field from the feature class.
    IFields featureClassFields=featureClass.Fields;
    IField field=featureClassFields.get_Field(fieldIndex);

    // Create a fields collection and add the specified field to it.
    IFields fields=new FieldsClass();
    IFieldsEdit fieldsEdit=(IFieldsEdit)fields;
    fieldsEdit.FieldCount_2=1;
    fieldsEdit.set_Field(0, field);

    // Create an index and cast to the IIndexEdit interface.
    IIndex index=new IndexClass();
    IIndexEdit indexEdit=(IIndexEdit)index;

    // Set the index's properties, including the associated fields.
    indexEdit.Fields_2=fields;
    indexEdit.IsAscending_2=false;
    indexEdit.IsUnique_2=false;
    indexEdit.Name_2=indexName;

    // Add the index to the feature class.
    featureClass.AddIndex(index);
}

Public Sub AddIndexToFeatureClass(ByVal featureClass As IFeatureClass, ByVal indexName As String, ByVal nameOfField As String)
    ' Ensure the feature class contains the specified field.
    Dim fieldIndex As Integer=featureClass.FindField(nameOfField)
    If fieldIndex=-1 Then
        Throw New ArgumentException("The specified field does not exist in the feature class.")
    End If
    
    ' Get the specified field from the feature class.
    Dim featureClassFields As IFields=featureClass.Fields
    Dim field As IField=featureClassFields.Field(fieldIndex)
    
    ' Create a fields collection and add the specified field to it.
    Dim fields As IFields=New FieldsClass()
    Dim fieldsEdit As IFieldsEdit=CType(fields, IFieldsEdit)
    fieldsEdit.FieldCount_2=1
    fieldsEdit.Field_2(0)=field
    
    ' Create an index and cast to the IIndexEdit interface.
    Dim index As IIndex=New IndexClass()
    Dim indexEdit As IIndexEdit=CType(index, IIndexEdit)
    
    ' Set the index's properties, including the associated fields.
    indexEdit.Fields_2=fields
    indexEdit.IsAscending_2=False
    indexEdit.IsUnique_2=False
    indexEdit.Name_2=indexName
    
    ' Add the index to the feature class.
    featureClass.AddIndex(index)
End Sub

Deleting an index

public void DeleteIndexByName(IFeatureClass featureClass, String indexName)
{
    // Find the index with the specified name.
    IIndexes indexes=featureClass.Indexes;
    int indexPos=0;
    indexes.FindIndex(indexName, out indexPos);
    if (indexPos < 0)
    {
        throw new ArgumentException("No index exists with the specified name.");
    }
    IIndex index=indexes.get_Index(indexPos);

    // Delete the index.
    featureClass.DeleteIndex(index);
}

Public Sub DeleteIndexByName(ByVal featureClass As IFeatureClass, ByVal indexName As String)
    ' Find the index with the specified name.
    Dim indexes As IIndexes=featureClass.Indexes
    Dim indexPos As Integer=0
    indexes.FindIndex(indexName, indexPos)
    If indexPos < 0 Then
        Throw New ArgumentException("No index exists with the specified name.")
    End If
    Dim index As IIndex=indexes.Index(indexPos)
    
    ' Delete the index.
    featureClass.DeleteIndex(index)
End Sub

Creating and rebuilding a spatial index

// Passing zero values for all three double parameters recalculates the spatial index with
// acceptable (but not necessarily optimal) values.
public void RebuildSpatialIndex(IFeatureClass featureClass, Double gridOneSize,
    Double gridTwoSize, Double gridThreeSize)
{
    // Get an enumerator for indexes based on the shape field.
    IIndexes indexes=featureClass.Indexes;
    String shapeFieldName=featureClass.ShapeFieldName;
    IEnumIndex enumIndex=indexes.FindIndexesByFieldName(shapeFieldName);
    enumIndex.Reset();

    // Get the index based on the shape field (should only be one) and delete it.
    IIndex index=enumIndex.Next();
    if (index != null)
    {
        featureClass.DeleteIndex(index);
    }

    // Clone the shape field from the feature class.
    int shapeFieldIndex=featureClass.FindField(shapeFieldName);
    IFields fields=featureClass.Fields;
    IField sourceField=fields.get_Field(shapeFieldIndex);
    IClone sourceFieldClone=(IClone)sourceField;
    IClone targetFieldClone=sourceFieldClone.Clone();
    IField targetField=(IField)targetFieldClone;

    // Open the geometry definition from the cloned field and modify it.
    IGeometryDef geometryDef=targetField.GeometryDef;
    IGeometryDefEdit geometryDefEdit=(IGeometryDefEdit)geometryDef;
    geometryDefEdit.GridCount_2=3;
    geometryDefEdit.set_GridSize(0, gridOneSize);
    geometryDefEdit.set_GridSize(1, gridTwoSize);
    geometryDefEdit.set_GridSize(2, gridThreeSize);

    // Create a spatial index and set the required attributes.
    IIndex newIndex=new IndexClass();
    IIndexEdit newIndexEdit=(IIndexEdit)newIndex;
    newIndexEdit.Name_2=String.Concat(shapeFieldName, "_Index");
    newIndexEdit.IsAscending_2=true;
    newIndexEdit.IsUnique_2=false;

    // Create a fields collection and assign it to the new index.
    IFields newIndexFields=new FieldsClass();
    IFieldsEdit newIndexFieldsEdit=(IFieldsEdit)newIndexFields;
    newIndexFieldsEdit.AddField(targetField);
    newIndexEdit.Fields_2=newIndexFields;

    // Add the spatial index back into the feature class.
    featureClass.AddIndex(newIndex);
}

' Passing zero values for all three double parameters recalculates the spatial index with
' acceptable (but not necessarily optimal) values.

Public Sub RebuildSpatialIndex(ByVal featureClass As IFeatureClass, ByVal gridOneSize As Double, ByVal gridTwoSize As Double, ByVal gridThreeSize As Double)
    
    ' Get an enumerator for indexes based on the shape field.
    Dim indexes As IIndexes=featureClass.Indexes
    Dim shapeFieldName As String=featureClass.ShapeFieldName
    Dim enumIndex As IEnumIndex=indexes.FindIndexesByFieldName(shapeFieldName)
    enumIndex.Reset()
    
    ' Get the index based on the shape field (should only be one) and delete it.
    Dim index As IIndex=enumIndex.Next()
    If Not index Is Nothing Then
        featureClass.DeleteIndex(index)
    End If
    
    ' Clone the shape field from the feature class.
    Dim shapeFieldIndex As Integer=featureClass.FindField(shapeFieldName)
    Dim fields As IFields=featureClass.Fields
    Dim sourceField As IField=fields.Field(shapeFieldIndex)
    Dim sourceFieldClone As IClone=CType(sourceField, IClone)
    Dim targetFieldClone As IClone=sourceFieldClone.Clone()
    Dim targetField As IField=CType(targetFieldClone, IField)
    
    ' Open the geometry definition from the cloned field and modify it.
    Dim geometryDef As IGeometryDef=targetField.GeometryDef
    Dim geometryDefEdit As IGeometryDefEdit=CType(geometryDef, IGeometryDefEdit)
    geometryDefEdit.GridCount_2=3
    geometryDefEdit.GridSize_2(0)=gridOneSize
    geometryDefEdit.GridSize_2(1)=gridTwoSize
    geometryDefEdit.GridSize_2(2)=gridThreeSize
    
    ' Create a spatial index and set the required attributes.
    Dim newIndex As IIndex=New IndexClass()
    Dim newIndexEdit As IIndexEdit=CType(newIndex, IIndexEdit)
    newIndexEdit.Name_2=String.Concat(shapeFieldName, "_Index")
    newIndexEdit.IsAscending_2=True
    newIndexEdit.IsUnique_2=False
    
    ' Create a fields collection and assign it to the new index.
    Dim newIndexFields As IFields=New FieldsClass()
    Dim newIndexFieldsEdit As IFieldsEdit=CType(newIndexFields, IFieldsEdit)
    newIndexFieldsEdit.AddField(targetField)
    newIndexEdit.Fields_2=newIndexFields
    
    ' Add the spatial index back into the feature class.
    featureClass.AddIndex(newIndex)
    
End Sub

See Also:

• ESRI.ArcGIS.System (ESRI.ArcGIS.esriSystem)
• ESRI.ArcGIS.Geodatabase