mirror of
https://github.com/berkeleydb/je.git
synced 2024-11-15 01:46:24 +00:00
246 lines
10 KiB
HTML
246 lines
10 KiB
HTML
|
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
|
|||
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|||
|
|
<html xmlns="http://www.w3.org/1999/xhtml">
|
|||
|
|
<head>
|
|||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
|
|||
|
|
<title>Chapter 4. Working with Indices</title>
|
|||
|
|
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
|||
|
|
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
|
|||
|
|
<link rel="start" href="index.html" title="Getting Started with Berkeley DB Java Edition" />
|
|||
|
|
<link rel="up" href="dpl.html" title="Part I. Programming with the Direct Persistence Layer" />
|
|||
|
|
<link rel="prev" href="saveret.html" title="Saving and Retrieving Data" />
|
|||
|
|
<link rel="next" href="dplindexcreate.html" title="Creating Indexes" />
|
|||
|
|
</head>
|
|||
|
|
<body>
|
|||
|
|
<div xmlns="" class="navheader">
|
|||
|
|
<div class="libver">
|
|||
|
|
<p>Library Version 12.2.7.5</p>
|
|||
|
|
</div>
|
|||
|
|
<table width="100%" summary="Navigation header">
|
|||
|
|
<tr>
|
|||
|
|
<th colspan="3" align="center">Chapter 4. Working with Indices</th>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="20%" align="left"><a accesskey="p" href="saveret.html">Prev</a> </td>
|
|||
|
|
<th width="60%" align="center">Part I. Programming with the Direct Persistence Layer</th>
|
|||
|
|
<td width="20%" align="right"> <a accesskey="n" href="dplindexcreate.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
<hr />
|
|||
|
|
</div>
|
|||
|
|
<div class="chapter" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h2 class="title"><a id="persist_index"></a>Chapter 4. Working with Indices</h2>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="toc">
|
|||
|
|
<p>
|
|||
|
|
<b>Table of Contents</b>
|
|||
|
|
</p>
|
|||
|
|
<dl>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect1">
|
|||
|
|
<a href="persist_index.html#dplindexaccess">Accessing Indexes</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
<dd>
|
|||
|
|
<dl>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect2">
|
|||
|
|
<a href="persist_index.html#primaryindexaccess">Accessing Primary Indices</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect2">
|
|||
|
|
<a href="persist_index.html#secondaryindexaccess">Accessing Secondary Indices</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
</dl>
|
|||
|
|
</dd>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect1">
|
|||
|
|
<a href="dplindexcreate.html">Creating Indexes</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
<dd>
|
|||
|
|
<dl>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect2">
|
|||
|
|
<a href="dplindexcreate.html#dplprimaryidxdecl">Declaring Primary Indexes</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect2">
|
|||
|
|
<a href="dplindexcreate.html#dplsecondaryidxdecl">Declaring Secondary Indexes</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect2">
|
|||
|
|
<a href="dplindexcreate.html#foreignkey">Foreign Key Constraints</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
</dl>
|
|||
|
|
</dd>
|
|||
|
|
</dl>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
All entity classes stored in JE using the DPL must have a
|
|||
|
|
primary index, or key, identified for them. All such classes may
|
|||
|
|
also have one or more secondary keys declared for them. This
|
|||
|
|
chapter describes primary and secondary indexes in detail, and
|
|||
|
|
shows how to access the indexes created for a given entity class.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
One way to organize access to your primary and secondary
|
|||
|
|
indexes is to create a <span class="emphasis"><em>data accessor</em></span>
|
|||
|
|
class. We show an implementation of a data accessor class in
|
|||
|
|
<a class="xref" href="simpleda.html" title="SimpleDA.class">SimpleDA.class</a>.
|
|||
|
|
</p>
|
|||
|
|
<div class="sect1" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h2 class="title" style="clear: both"><a id="dplindexaccess"></a>Accessing Indexes</h2>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="toc">
|
|||
|
|
<dl>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect2">
|
|||
|
|
<a href="persist_index.html#primaryindexaccess">Accessing Primary Indices</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
<dt>
|
|||
|
|
<span class="sect2">
|
|||
|
|
<a href="persist_index.html#secondaryindexaccess">Accessing Secondary Indices</a>
|
|||
|
|
</span>
|
|||
|
|
</dt>
|
|||
|
|
</dl>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
In order to retrieve any object from an entity store, you
|
|||
|
|
must access at least the primary index for that object.
|
|||
|
|
Different entity classes stored in an entity store can have
|
|||
|
|
different primary indexes, but all entity classes must have a
|
|||
|
|
primary index declared for it. The primary index is just
|
|||
|
|
the default index used for the class. (That is, it is the
|
|||
|
|
data's primary <span class="emphasis"><em>key</em></span> for the underlying database.)
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Entity classes can optionally have secondary indexes
|
|||
|
|
declared for them. In order to access these secondary
|
|||
|
|
indexes, you must first access the primary index.
|
|||
|
|
</p>
|
|||
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h3 class="title"><a id="primaryindexaccess"></a>Accessing Primary Indices</h3>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
You retrieve a primary index using the
|
|||
|
|
<code class="methodname">EntityStore.getPrimaryIndex()</code>
|
|||
|
|
method. To do this, you indicate the index key type
|
|||
|
|
(that is, whether it is a String, Integer, and
|
|||
|
|
so forth) and the class of the entities stored
|
|||
|
|
in the index.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
For example, the following retrieves the
|
|||
|
|
primary index for an <code class="classname">Inventory</code>
|
|||
|
|
class (we provide an implementation of this class in
|
|||
|
|
<a class="xref" href="inventoryclass.html" title="Inventory.java">Inventory.java</a>).
|
|||
|
|
These index keys are of type <code class="classname">String</code>.
|
|||
|
|
</p>
|
|||
|
|
<pre class="programlisting">PrimaryIndex<String,Inventory> inventoryBySku =
|
|||
|
|
store.getPrimaryIndex(String.class, Inventory.class); </pre>
|
|||
|
|
</div>
|
|||
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h3 class="title"><a id="secondaryindexaccess"></a>Accessing Secondary Indices</h3>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
You retrieve a secondary index using the
|
|||
|
|
<code class="methodname">EntityStore.getSecondaryIndex()</code>
|
|||
|
|
method. Because secondary indices actually
|
|||
|
|
refer to a primary index somewhere in your data
|
|||
|
|
store, to access a secondary index you:
|
|||
|
|
</p>
|
|||
|
|
<div class="orderedlist">
|
|||
|
|
<ol type="1">
|
|||
|
|
<li>
|
|||
|
|
<p>
|
|||
|
|
Provide the primary index as
|
|||
|
|
returned by
|
|||
|
|
<code class="methodname">EntityStore.getPrimaryIndex()</code>.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p>
|
|||
|
|
Identify the key data type used by
|
|||
|
|
the secondary index
|
|||
|
|
(<code class="classname">String</code>,
|
|||
|
|
<code class="classname">Long</code>,
|
|||
|
|
and so forth).
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p>
|
|||
|
|
Identify the name of the
|
|||
|
|
secondary key field.
|
|||
|
|
When you declare the
|
|||
|
|
<code class="classname">SecondaryIndex</code>
|
|||
|
|
object, you identify the entity class
|
|||
|
|
to which the secondary index
|
|||
|
|
must refer.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
</ol>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
For example, the following first retrieves the
|
|||
|
|
primary index, and then uses that to retrieve a secondary
|
|||
|
|
index. The secondary key is held by the
|
|||
|
|
<code class="literal">itemName</code> field of the
|
|||
|
|
<code class="classname">Inventory</code> class.
|
|||
|
|
</p>
|
|||
|
|
<pre class="programlisting">PrimaryIndex<String,Inventory> inventoryBySku =
|
|||
|
|
store.getPrimaryIndex(String.class, Inventory.class);
|
|||
|
|
|
|||
|
|
SecondaryIndex<String,String,Inventory> inventoryByName =
|
|||
|
|
store.getSecondaryIndex(inventoryBySku, String.class, "itemName"); </pre>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="navfooter">
|
|||
|
|
<hr />
|
|||
|
|
<table width="100%" summary="Navigation footer">
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left"><a accesskey="p" href="saveret.html">Prev</a> </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="u" href="dpl.html">Up</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right"> <a accesskey="n" href="dplindexcreate.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left" valign="top">Saving and Retrieving Data </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="h" href="index.html">Home</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right" valign="top"> Creating Indexes</td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
</div>
|
|||
|
|
</body>
|
|||
|
|
</html>
|