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%7D

-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 +@uref{http://opensource.franz.com/preamble.html%7D, 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}:

-@uref{http://oss.software.ibm.com/icu/%7D +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 -of this license document, but changing it is not allowed.

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--- /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 -@subtitle Elephant version 0.2 +@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. + +@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%7D. +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%7D.

-@node Getting Started -@comment node-name, next, previous, up -@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 -@code{testdb} in the current directory. +@node Running the Tests +@comment node-name, next, previous, up +@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 +@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) -@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) +@end lisp

+The SQL test file differs only in using a different ``controller spec'': +@lisp(setf *default-spec* *testpg-spec*) +@end lisp +These default parameters are set in @file{tests/elephant-tests.lisp}, +they will looks something like this in a default distribution: +@lisp +(:BDB "/home/read/projects/sql-back-end/elephant/tests/testdb/") +@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 +@node Getting Started +@comment node-name, next, previous, up +@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.

-@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 +@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: +@lisp +(open-store *default-spec*) +@end lisp +But if not you might have to set up your own controller specifier like this: +@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.

+ +@node Class Indices +@comment node-name, next, previous, up +@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. + +@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)) +@end lisp + +Additionally, the test +@lisp +(do-test 'INDEXING-TIMING) +@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: + +@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)) +@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