[elephant-cvs] CVS elephant/doc
rread
rread at common-lisp.net
Thu Mar 2 14:44:49 UTC 2006
Update of /project/elephant/cvsroot/elephant/doc
In directory clnet:/tmp/cvs-serv6190
Modified Files:
copying.texinfo elephant.texinfo intro.texinfo
tutorial.texinfo
Log Message:
An attempt to improve the documentation, especially around class indexing.
--- /project/elephant/cvsroot/elephant/doc/copying.texinfo 2004/09/19 17:44:43 1.1
+++ /project/elephant/cvsroot/elephant/doc/copying.texinfo 2006/03/02 14:44:49 1.2
@@ -11,342 +11,27 @@
Homepage: @uref{http://www.common-lisp.net/project/elephant}
-Copyright (c) 2004 by Andrew Blumberg and Ben Lee
+Elephant users are granted the rights to distribute and use this software
+as governed by the terms of the Lisp Lesser GNU Public License
+ at uref{http://opensource.franz.com/preamble.html}, also known as the LLGPL.
-This program is released under the following license
-("GPL"). For differenct licensing terms, contact the
-copyright holders.
-Portions of this program (namely the C unicode string
-sorter) are derived from IBM's @b{ICU}:
- at uref{http://oss.software.ibm.com/icu/}
+Copyrights include:
-whose copyright and license follows the GPL below.
+Copyright (c) 2004 by Andrew Blumberg and Ben Lee
-The GNU General Public License (GPL)
-Version 2, June 1991
+Copyright (c) 2006 by Ian Eslick
-Copyright (C) 1989, 1991 Free Software Foundation, Inc.
-59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+Copyright (c) 2005,2006 by Robert L. Read
-Everyone is permitted to copy and distribute verbatim copies
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+Portions of this program (namely the C unicode string
+sorter) are derived from IBM's @b{ICU}:
-END OF TERMS AND CONDITIONS
+ at uref{http://oss.software.ibm.com/icu/}
+
+whose copyright and license follows the GPL below.
--- /project/elephant/cvsroot/elephant/doc/elephant.texinfo 2006/01/24 20:37:43 1.3
+++ /project/elephant/cvsroot/elephant/doc/elephant.texinfo 2006/03/02 14:44:49 1.4
@@ -6,6 +6,7 @@
@copying
Copyright @copyright{} 2004 Ben Lee and Andrew Blumberg.
+Copyright @copyright{} 2006 Robert L. Read.
@quotation
Permission is granted to copy, distribute and/or modify this document
@@ -18,7 +19,7 @@
@titlepage
@title Elephant User Manual
- at subtitle Elephant version 0.2
+ at subtitle Elephant version 0.6
@author Ben Lee
@c The following two commands
--- /project/elephant/cvsroot/elephant/doc/intro.texinfo 2005/11/23 18:14:11 1.2
+++ /project/elephant/cvsroot/elephant/doc/intro.texinfo 2006/03/02 14:44:49 1.3
@@ -7,17 +7,16 @@
Elephant is an object database for Common Lisp. It supports
storing CLOS objects and most lisp primitives, and access to
-BTrees. It uses Sleepycat / Berkeley DB, a
+BTrees. It can use the Sleepycat / Berkeley DB, a
widely-distributed embedded database; many unix systems have
it installed by default. Sleepycat is server-less, ACID
compliant, transactional, process and thread safe, and fast
relative to relational databases; hopefully Elephant
inherits these properties.
-This release, Elephant 0.3, also provieds support for
-relational backends. It has been tested with Postgres and SQLite 3.
-It is back-compatible with any code that ran against previous
-versions of Elephant, but also supports simultaneous multi-repository
+It also provieds support for relational backends.
+It has been tested with Postgres and SQLite 3.
+It supports simultaneous multi-repository
operation and convenient migration of data between repositories.
This hopefully allows decisions about the prefered back-end
storage mechanism to be delayed and changed, even after
@@ -41,8 +40,14 @@
@item Performance: leverage Sleepycat performance and
reliability. In addition to fast concurrent / transactional modes,
elephant will (eventually) offer an accellerated single-user mode.
+
+ at item License Flexibility: Elephant is released under the LLGPL.
+Because it supports multiple implementation of the backend, one
+can choose a backend with licensing and other features appropriate to your needs.
@end itemize
+
+
Join the Elephant mailing lists to ask your questions and
receive updates. They're on the Elephant website at
--- /project/elephant/cvsroot/elephant/doc/tutorial.texinfo 2006/01/24 20:37:43 1.4
+++ /project/elephant/cvsroot/elephant/doc/tutorial.texinfo 2006/03/02 14:44:49 1.5
@@ -8,6 +8,7 @@
@menu
* Preliminaries:: Some general remarks.
* Getting Started:: Accessing a store.
+* Running the Tests:: Gaining confidence.
* The Root:: Staying alive.
* Serialization:: Lisp -> (char *).
* Persistent Classes:: CLOS the Elephant way.
@@ -15,6 +16,7 @@
* Using Transactions:: Using ACID.
* Using BTrees:: Storing lots of things.
* Using Cursors:: Tranversing BTrees.
+* Class Indices:: Speed and Convenience.
* Secondary Indices:: by any other name...
* The Store Controller:: behind the curtain.
* Threading:: Playing nice with others.
@@ -25,51 +27,122 @@
@comment node-name, next, previous, up
@section Preliminaries
+Elephant isa Common Lisp OODB. It solves the problem of
+making Lisp data persistent. It does this through two mechanisms:
+a very simple API, and the ability to declare a CLOS class to be
+persistent. It offers simple and powerful functional indexes
+as well as convenient slot-based indexes. It represents
+
Elephant is an Common Lisp OODB, as opposed to a language-neutral
-(e.g. language-unspecific) RDBMS. This means it can store most Lisp
-values without programmer intervention, special syntax or laborious
+(e.g. language-unspecific) RDBMS. This means it can store and efficient index
+most Lisp values without programmer intervention, special syntax or laborious
conversion. In that way it is similar to prevalence, but it is
actually a database: it is not in-memory (though it can be.)
When someone says "database," most people think of SQL RDBMSs (oracle,
-postgresql, mysql). Elephant uses Berekely DB (Sleepycat) which is
-much simpler: there is no special SQL relational syntax, just access
-to BTrees and other datatypes. It is a C library, not a server. On
+postgresql, mysql). Elephant uses RDBMSs or Berekely DB (Sleepycat) as
+a data repository, but simply uses LISP as its data manipulation system.
+Unlike systems such as Hibernate for Java, the user does not need to
+construct or worry about a mapping from the object space into
+the database. Elephant is a very convenient system for the
+programmer.
+
+Elephant can employ several different data repositories as a ``back-ends''.
+It also supports easy migration of data between these repositories,
+which allows the user to flexibly choose, or to late-bind, which
+repository will use at a particular point in time.
+
+
+Berkeley DB/Sleepycat is a very fast database that is well-matched
+to Elephant.
+Berkeley DB is a C library, not a server. On
the other hand it is quite robust, and has many features, like
transactions and replication. While you don't need to understand
-Sleepycat to use Elephant, reading the docs will certainly help you.
-They can be found at @uref{http://www.sleepycat.com}.
+a specific backend to use Elephant, reading the docs will certainly help you.
+For the Sleepycat backend, they can be found at @uref{http://www.sleepycat.com}.
- at node Getting Started
- at comment node-name, next, previous, up
- at section Getting Started
+Elephant can also employ relational databases, based on the excellent CL-SQL
+package. It has been tested with Postgres and SQLite3, and can probably easily
+work with others.
-Make a directory to put your database store in. (This is called the
-environment in Sleepycat terminology.) That's all you need to set up
-your store! We'll assume in this tutorial you created a folder
- at code{testdb} in the current directory.
+ at node Running the Tests
+ at comment node-name, next, previous, up
+ at section Running the Tests
-Assuming you've managed to install Elephant properly, and
-are using a BerkeleyDB installation.
+There are three files in the directory @code{tests} that make running
+the automated tests particularly easy. @code{BerkeleyDB-tests.lisp} is
+for running against the BerkeleyDB backend, and @code{SQLDB-tests.lisp} is
+for running agains the CL-SQL backend. @code{MigrationTests.lisp} is
+for testing data migration functions, and can be used with either or both backends.
+The normal way to execute the tests, following the instruction in the file
+ at code{INSTALL}, is to open a listener and execute the lines found in
+one of these files, such as:
@lisp
-* (asdf:operate 'asdf:load-op :elephant)
-* (asdf:operate 'asdf:load-op :ele-bdb)
- at end lisp
+(asdf:operate 'asdf:load-op :elephant-tests)
-will load the relevant files.
+(in-package "ELEPHANT-TESTS")
+
+(setf *default-spec* *testbdb-spec*)
+
+(do-backend-tests)
+ at end lisp
+The SQL test file differs only in using a different ``controller spec'':
+ at lisp(setf *default-spec* *testpg-spec*)
+ at end lisp
+These default parameters are set in @file{tests/elephant-tests.lisp},
+they will looks something like this in a default distribution:
+ at lisp
+(:BDB "/home/read/projects/sql-back-end/elephant/tests/testdb/")
+ at end lisp
+and for postgres:
@lisp
-* (use-package "ELE")
+(:CLSQL (:POSTGRESQL "localhost.localdomain" "test" "postgres" ""))
@end lisp
-will make all the necessary symbols available.
-To make your store available to Lisp, do
+ at node Getting Started
+ at comment node-name, next, previous, up
+ at section Getting Started
+
+In order to use Elephant, you have to have an open store controller.
+To obtain an open store controller, you have to decide which back-end
+you will use and properly install that back-end system. The actual
+use of Elephant once you have an open store controller is almost
+completely independent of what the actual back-end choice is; Elephant
+attempts to abstract away all such details.
+
+The chapter ``SQL back-end'' has information about setting up a
+SQL based backend; this tutorial will assume that you are using
+Berkeley-DB as a backend.
- at lisp
-* (open-store "testdb")
-=> #<STORE-CONTROLLER @{49252F75@}>
+Make a directory to put your database store in. (This is called the
+environment in Sleepycat terminology.) That's all you need to set up
+your store! We'll assume in this tutorial you created a folder
+ at code{testdb} in the current directory.
+
+It is strongly recommended that you run the automated tests @xref{Running the Tests} that
+come with Elephant before you begin this tutorial; this takes less
+than five minutes and if will give you both confidence and clarity
+and your continued work. Since the default distribution comes
+with a directory structure set up, this is actually the easiest
+way to get started with Elephant before beginning this tutorial.
+If the tests fail for you, the Elephant developers will help you
+solve the problem, but will want to know the outcome of the tests
+as a starting point.
+
+If you have run the tests successfully, you can just do:
+ at lisp
+(open-store *default-spec*)
+ at end lisp
+But if not you might have to set up your own controller specifier like this:
+ at lisp
+(asdf:operate 'asdf:load-op :elephant)
+(use-package "ELE")
+(setf *testbdb-spec*
+'(:BDB "/home/read/projects/sql-back-end/elephant/tests/testdb/"))
+(open-store *testbdb-spec*)
@end lisp
When you're done with your session, don't forget to
@@ -484,6 +557,89 @@
@code{map-btree} function, which functions analogously to the
@code{maphash} CL function.
+
+ at node Class Indices
+ at comment node-name, next, previous, up
+ at section Class Indices
+
+Class indices are a very convenient way of gaining the efficiency
+that indexes provide. If a given object is most often sought by
+the value of one of its slots, which is of course quite common,
+it is convenient to define a class index on that slot, although
+the same functionality can be gained in a more complicated way through
+the use fo secondary indices.
+
+The file @file{tests/testindexing.lisp} provides many useful examples
+of both declaring class indexes and using the API to seek objects using them.
+
+The following code from that file in the test ``indexing-range'' demonstrates
+the convenience of a class indexes and the function ``get-instances-by-range''.
+Note in the definiton of the ``slot1'' the keyword ``:index'' is used to
+specify that this slot should be indexed.
+
+ at lisp
+ (defclass idx-four ()
+ ((slot1 :initarg :slot1 :initform 1 :accessor slot1 :index t))
+ (:metaclass persistent-metaclass))
+
+
+ (defun make-idx-four (val)
+ (make-instance 'idx-four :slot1 val))
+
+ (with-transaction ()
+ (mapc #'make-idx-four '(1 1 1 2 2 4 5 5 5 6 10)))
+
+ (let ((x1 (get-instances-by-range 'idx-four 'slot1 2 6))
+ (x2 (get-instances-by-range 'idx-four 'slot1 0 2))
+ (x3 (get-instances-by-range 'idx-four 'slot1 6 15))
+ )
+ (format t " x1 = ~A~%" (mapcar #'slot1 x1))
+ (format t " x2 = ~A~%" (mapcar #'slot1 x2))
+ (format t " x3 = ~A~%" (mapcar #'slot1 x3))
+ at end lisp
+
+Additionally, the test
+ at lisp
+(do-test 'INDEXING-TIMING)
+ at end lisp
+Can be used to judge the performance of indexing a large dataset.
+
+The file @file{src/elephant/classindex.lisp} provides the source code and
+some crisp documentation of the class indexing system.
+
+Note that for retrieving items, the API is provided by three functions:
+
+ at lisp
+(defgeneric get-instances-by-class (persistent-metaclass))
+(defgeneric get-instances-by-value (persistent-metaclass slot-name value))
+(defgeneric get-instances-by-range (persistent-metaclass slot-name start end))
+ at end lisp
+
+By using these functions, any class that is a subclass of persistent-metaclass
+can also be thought of a as a container of all of its instances, which are
+persistent in the database between lisp invocations. Morover an individual
+object can be looked up on O(log n) time via a value which is indexed.
+
+At the top of this same file, you will find the a description of the API
+which can be used to dynamically add and remove indexes. (Adding and
+removing indexes can also be performed by a re-execution of the ``defclass''
+macro with different values.)
+
+Thus, the question of if and how a given class should be indexed is
+very flexible and dynamic, and does not need to be determined at the
+beginning of your development. This represents the ability to ``late bind''
+the and change the decision of what to index for efficiencty.
+
+In general, there is always a tradeoff: an index makes reads in a
+particular way fast, but makes writes slower. The Elephant system
+makes it simple to choose where and when one wants to utilize this tradeoff.
+
+Finally, that file @file{src/elephant/classindex-utils.lisp} documents
+tools for handling class redefinitions and the policy that should be
+used for synchronizing the classes with the database.
+
+Thanks to Ian Eslick for this functionality.
+
@node Secondary Indices
@comment node-name, next, previous, up
@section Secondary Indices
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