.. _index_dialog:

****************
The Index Dialog
****************
 
Use the *Index* dialog to create an index on a specified table or materialized view.

The *Index* dialog organizes the development of a index through the following dialog tabs: *General* and *Definition*. The *SQL* tab displays the SQL code generated by dialog selections. 

.. image:: images/index_general.png

Use the fields in the *General* tab to identify the index:

* Use the *Name* field to add a descriptive name for the index. The name will be displayed in the *pgAdmin* tree control.
* Use the drop-down listbox next to *Tablespace* to select the tablespace in which the index will reside. 
* Store notes about the index in the *Comment* field.

Click the *Definition* tab to continue.

.. image:: images/index_definition.png

Use the fields in the *Definition* tab to define the index:  

* Use the drop-down listbox next to *Access Method* to select an index type:

    * Select *btree* to create a B-tree index.  A B-tree index may improve performance when managing equality and range queries on data that can be sorted into some ordering (the default).
    * Select *hash* to create a hash index.  A hash index may improve performance when managing simple equality comparisons.
    * Select *gist* to create a GiST index.  A GiST index may improve performance when managing values with more than one key.
    * Select *gin* to create a GIN index.  A GIN index may improve performance when managing two-dimensional geometric data types and nearest-neighbor searches.
    * Select *spgist* to create a space-partitioned GiST index. A SP-GiST index may improve performance when managing non-balanced data structures.
    * Select *brin* to create a BRIN index.  A BRIN index may improve performance when managing minimum and maximum values and ranges.
   
* Use the *Fill Factor* field to specify a fill factor for the index. The fill factor specifies how full the selected method will try to fill each index page.
* Move the *Unique?* switch to the *Yes* position to check for duplicate values in the table when the index is created and when data is added. The default is *No*.
* Move the *Clustered?* switch to the *Yes* position to instruct the server to cluster the table.
* Move the *Concurrent build?* switch to the *Yes* position to build the index without taking any locks that prevent concurrent inserts, updates, or deletes on the table.
* Use the *Constraint* field to provide a constraint expression; a constraint expression limits the entries in the index to those rows that satisfy the constraint.

Use the context-sensitive fields in the *Columns* panel to specify which column(s) the index queries. Click the *Add* icon (+) to add a column:

* Use the drop-down listbox in *Column* field to select the name of the column from the table.
* If enabled, use the drop-down listbox to select an available *Operator class* to specify the type of action performed on the column.
* If enabled, move the *Sort order* switch to specify the sort order:

    * Select *ASC* to specify an ascending sort order (the default);
    * Select *DESC* to specify a descending sort order.
   
* If enabled, move the *Nulls* switch to specify the sort order of nulls:

    * Select *First* to specify nulls sort before non-nulls;
    * Select *Last* to specify nulls sort after non-nulls (the default).
   
* Use the drop-down listbox in the *Collation* field to select a collation to use for the index.

Click the *SQL* tab to continue.

Your entries in the *Index* dialog generate a SQL command (see an example below). Use the *SQL* tab for review; revisit or switch tabs to make any changes to the SQL command. 

**Example**

The following is an example of the sql command generated by user selections in the *Index* dialog: 

.. image:: images/index_sql.png

The example shown demonstrates creating an index named *dist_codes* that indexes the values in the *code* column of the *distributors* table.
 
* Click the *Info* button (i) to access online help. View context-sensitive help in the *Tabbed browser*, where a new tab displays the PostgreSQL core documentation.
* Click the *Save* button to save work.
* Click the *Cancel* button to exit without saving work.
* Click the *Reset* button to restore configuration parameters.