Merge arjen@work.mysql.com:/home/bk/mysql-4.0

* MySQL Information Sources::   MySQL Information Sources

* Compatibility::               How Standards-compatible Is MySQL?

* TODO::                        MySQL and the future (The TODO)

* Comparisons::                 How MySQL Compares to Other Open Source Databases

@end menu

For platform-specific bugs, see the sections about compiling and porting.

@node TODO,  , Compatibility, Introduction

@node TODO, Comparisons, Compatibility, Introduction

@section MySQL and The Future (The TODO)

@cindex ToDo list for MySQL

@end itemize

@node Comparisons,  , TODO, Introduction

@section How MySQL Compares to Other Open Source Databases

@cindex databases, MySQL vs. others

@cindex comparisons, MySQL vs. others

Our users have successfully run their own benchmarks against a number

of @code{Open Source} and traditional database servers. We are aware of

tests against @code{Oracle}, @code{DB/2}, @code{Microsoft SQL Server}

and other commercial products. Due to legal reasons we are restricted

from publishing some of those benchmarks in our reference manual.

This section includes a comparison with @code{PostgreSQL} as it is

also an Open Source database. If you have benchmark results that we

can publish, please contact us at @email{benchmarks@@mysql.com}.

For comparative lists of all supported functions and types as well

as measured operational limits of many different database systems,

see the @code{crash-me} web page at

@uref{http://www.mysql.com/information/crash-me.php}.

@menu

* Compare PostgreSQL::          How MySQL Compares to PostgreSQL

@end menu

@node Compare PostgreSQL,  , Comparisons, Comparisons

@subsection How MySQL Compares to PostgreSQL

@cindex PostgreSQL vs. MySQL, overview

When reading the following, please note that both products are continually

evolving.  We at MySQL AB and the PostgreSQL developers are both working

on making our respective database as good as possible, so we are both a 

serious alternative to any commercial database.

The following comparison is made by us at MySQL AB.  We have tried to be

as accurate and fair as possible, but because while we know MySQL througly

we don't have a full knowledge of all PostgreSQL features, so we may have

got some things wrong.  We will however correct these when they come to our

attention.

We would first like to note that PostgreSQL and MySQL are both widely used

products, but with different design goals, even if we are both striving

towards ANSI SQL compliancy.  This means that for some applications MySQL

is more suited, while for others PostgreSQL is more suited.  When choosing 

which database to use, you should first check if the database's feature set

satisfies your application.  If you need raw speed, MySQL is probably your

best choice.  If you need some of the extra features that only PostgreSQL

can offer, you should use @code{PostgreSQL}.

@menu

* MySQL-PostgreSQL goals::      MySQL and PostgreSQL development strategies

* MySQL-PostgreSQL features::   Featurewise Comparison of MySQL and PostgreSQL

@end menu

@node MySQL-PostgreSQL goals, MySQL-PostgreSQL features, Compare PostgreSQL, Compare PostgreSQL

@subsubsection MySQL and PostgreSQL development strategies

@cindex PostgreSQL vs. MySQL, strategies

When adding things to MySQL we take pride to do an optimal, definite

solution.  The code should be so good that we shouldn't have any need to

change it in the foreseeable future.  We also do not like to sacrifice

speed for features but instead will do our utmost to find a solution

that will give maximal throughput.  This means that development will take

a little longer, but the end result will be well worth this.  This kind

of development is only possible because all server code are checked by

one of a few (currently two) persons before it's included in the

MySQL server.

We at MySQL AB believe in frequent releases to be able to push out new

features quickly to our users.  Because of this we do a new small release

about every three weeks, and a major branch every year.  All releases are

throughly tested with our testing tools on a lot of different platforms.

PostgreSQL is based on a kernel with lots of contributors. In this setup

it makes sense to prioritise adding a lot of new features, instead of

implementing them optimally, because one can always optimise things

later if there arises a need for this.

Another big difference between MySQL and PostgreSQL is that

nearly all of the code in the MySQL server are coded by developers that

are employed by MySQL AB and are still working on the server code. The

exceptions are the transaction engines, and the regexp library.

This is in sharp contrast to the PostgreSQL code where the majority of

the code is coded by a big group of people with different backgrounds.

It was only recently that the PostgreSQL developers announced that their

current developer group had finally had time to take a look at all

the code in the current PostgreSQL release.

Both of the above development methods have their own merits and drawbacks.

We here at MySQL AB think of course that our model is better because our

model gives better code consistency, more optimal and reusable code, and

in our opinion, fewer bugs.  Because we are the authors of the MySQL server

code, we are better able to coordinate new features and releases.

@node MySQL-PostgreSQL features,  , MySQL-PostgreSQL goals, Compare PostgreSQL

@subsubsection Featurewise Comparison of MySQL and PostgreSQL

@cindex PostgreSQL vs. MySQL, features

On the crash-me page

(@uref{http://www.mysql.com/information/crash-me.php})

you can find a list of those database constructs and limits that

one can detect automatically with a program.  Note however that a lot of

the numerical limits may be changed with startup options for respective

database.  The above web page is however extremely useful when you want to

ensure that your applications works with many different databases or

when you want to convert your application from one database to another.

MySQL offers the following advantages over PostgreSQL:

@itemize @bullet

@item

@code{MySQL} is generally much faster than PostgreSQL.

@item

MySQL has a much larger user base than PostgreSQL, therefore the

code is more tested and has historically proven more stable than

PostgreSQL.  MySQL is the much more used in production

environments than PostgreSQL, mostly thanks to that MySQL AB,

formerly TCX DataKonsult AB, has provided top quality commercial support

for MySQL from the day it was released, whereas until recently

PostgreSQL was unsupported.

@item

MySQL works better on Windows than PostgreSQL does.  MySQL runs as a

native Windows application (a service on NT/Win2000/WinXP), while

PostgreSQL is run under the @code{Cygwin} emulation.  We have heard

that PostgreSQL is not yet that stable on Windows but we haven't

been able to verify this ourselves.

@item

MySQL has more APIs to other languages and is supported by more

existing programs than PostgreSQL.  @xref{Contrib}.

@item

MySQL works on 24/7 heavy duty systems.  In most circumstances

you never have to run any cleanups on MySQL.  PostgreSQL doesn't

yet support 24/7 systems because you have to run @code{VACUUM()}

once in a while to reclaim space from @code{UPDATE} and @code{DELETE}

commands and to perform statistics analyses that are critical to get

good performance with PostgreSQL.  @code{VACUUM()} is also needed after

adding a lot of new rows to a table.  On a busy system with lots of changes,

@code{VACUUM()} must be run very frequently, in the worst cases even 

many times a day.  During the @code{VACUUM()} run, which may take hours 

if the database is big, the database is from a production standpoint,

practically dead.  The PostgreSQL team has fixing this on their TODO,

but we assume that this is not an easy thing to fix permanently.

@item

MySQL replication has been thoroughly tested, and is used by sites like:

@itemize @minus

@item Yahoo Finance (@uref{http://finance.yahoo.com/})

@item Mobile.de (@uref{http://www.mobile.de/})

@item Slashdot (@uref{http://www.slashdot.org/})

@end itemize

@item

Included in the MySQL distribution are two different testing suites, 

@file{mysql-test-run} and crash-me

(@uref{http://www.mysql.com/information/crash-me.php}), as well

as a benchmark suite.  The test system is actively updated with code to

test each new feature and almost all reproduceable bugs that have come to

our attention.  We test MySQL with these on a lot of platforms before

every release.  These tests are more sophisticated than anything we have 

seen from PostgreSQL, and they ensures that the MySQL is kept to a high

standard.

@item

There are far more books in print about MySQL than about PostgreSQL.

O'Reilly, SAMS, Que, and New Riders are all major publishers with books

about MySQL.  All MySQL features are also documented in the MySQL on-line

manual, because when a new feature is implemented, the MySQL developers 

are required to document it before it's included in the source.

@item

MySQL supports more of the standard ODBC functions than @code{PostgreSQL}.

@item

MySQL has a much more sophisticated @code{ALTER TABLE}.

@item

MySQL has support for tables without transactions for applications that 

need all speed they can get. The tables may be memory based, @code{HEAP}

tables or disk based @code{MyISAM}.  @xref{Table types}.

@item

MySQL has support for two different table handlers that support

transactions, @code{InnoDB} and @code{BerkeleyDB}.  Because every 

transaction engine performs differently under different conditions, this 

gives the application writer more options to find an optimal solution for

his or her setup, if need be per individual table.  @xref{Table types}.

@item

@code{MERGE} tables gives you a unique way to instantly make a view over

a set of identical tables and use these as one.  This is perfect for

systems where you have log files that you order for example by month.

@xref{MERGE}.

@item

The option to compress read-only tables, but still have direct access to

the rows in the table, gives you better performance by minimising disk

reads.  This is very useful when you are archiving things.

@xref{myisampack}.

@item

MySQL has internal support for fulltext search. @xref{Fulltext Search}.

@item

You can access many databases from the same connection (depending of course

on your privileges).

@item

MySQL is coded from the start to be multi-threaded while PostgreSQL uses

processes.  Context switching and access to common storage areas is much 

faster between threads than between separate processes, this gives MySQL

a big speed advantage in multi-user applications and also makes it easier

for MySQL to take full advantage of symmetric multiprocessor (SMP) systems.

@item

MySQL has a much more sophisticated privilege system than PostgreSQL.  

While PostgreSQL only supports @code{INSERT}, @code{SELECT}, and

@code{UPDATE/DELETE} grants per user on a database or a table, MySQL allows

you to define a full set of different privileges on database, table and 

column level.  MySQL also allows you to specify the privilege on host and 

user combinations.  @xref{GRANT}.

@item

MySQL supports a compressed client/server protocol which improves 

performance over slow links.

@item

MySQL employs a ``table handler'' concept, and is the only relational 

database we know of built around this concept.  This allows different 

low-level table types to be called from the SQL engine, and each table 

type can be optimised for different performance characteristics.

@item

All MySQL table types (except @strong{InnoDB}) are implemented as files

(one table per file), which makes it really easy to backup, move, delete

and even symlink databases and tables, even when the server is down.

@item

Tools to repair and optimise @strong{MyISAM} tables (the most common

MySQL table type).  A repair tool is only needed when a physical corruption

of a data file happens, usually from a hardware failure.  It allows a 

majority of the data to be recovered.

@item

Upgrading MySQL is painless.  When you are upgrading MySQL, you don't need

to dump/restore your data, as you have to do with most PostgreSQL upgrades.

@end itemize

Drawbacks with MySQL compared to PostgreSQL:

@itemize @bullet

@item

The transaction support in MySQL is not yet as well tested as PostgreSQL's

system.

@item

Because MySQL uses threads, which are not yet flawless on many OSes, one

must either use binaries from @uref{http://www.mysql.com/downloads/}, or

carefully follow our instructions on

@uref{http://www.mysql.com/doc/I/n/Installing_source.html} to get an

optimal binary that works in all cases.

@item

Table locking, as used by the non-transactional @code{MyISAM} tables, is

in many cases faster than page locks, row locks or versioning.  The

drawback however is that if one doesn't take into account how table

locks work, a single long-running query can block a table for updates

for a long time. This can usually be avoided when designing the

application.  If not, one can always switch the trouble table to use one

of the transactional table types. @xref{Table locking}.

@item

With UDF (user defined functions) one can extend MySQL with both normal 

SQL functions and aggregates, but this is not yet as easy or as flexible

as in PostgreSQL.  @xref{Adding functions}.

@item

Updates that run over multiple tables is harder to do in MySQL.

This will, however, be fixed in MySQL 4.0 with multi-table @code{UPDATE}

and in MySQL 4.1 with subselects.

In MySQL 4.0 one can use multi-table deletes to delete from many tables

at the same time. @xref{DELETE}.

@end itemize

PostgreSQL currently offers the following advantages over MySQL:

Note that because we know the MySQL road map, we have included in the

following table the version when MySQL should support this feature.

Unfortunately we couldn't do this for previous comparison, because we 

don't know the PostgreSQL roadmap.

@multitable @columnfractions .70 .30

@item @strong{Feature}                     @tab @strong{MySQL version}

@item Subselects                           @tab 4.1

@item Foreign keys                         @tab 4.0 and 4.1

@item Views                                @tab 4.2

@item Stored procedures                    @tab 4.1

@item Extensible type system               @tab Not planned

@item Unions                               @tab 4.0

@item Full join                            @tab 4.0 or 4.1

@item Triggers                             @tab 4.1

@item Constraints                          @tab 4.1

@item Cursors                              @tab 4.1 or 4.2

@item Extensible index types like R-trees  @tab R-trees are planned for 4.2

@item Inherited tables                     @tab Not planned

@end multitable

Other reasons someone may consider for using PostgreSQL:

@itemize @bullet

@item

Standard usage in PostgreSQL is closer to ANSI SQL in some cases.

@item

One can speed up PostgreSQL by coding things as stored procedures.

@item

For geographical data, R-TREES makes PostgreSQL better than MySQL.

@item

The PostgreSQL optimiser can do some optimisation that the current MySQL

optimiser can't do.  Most notable is doing joins when you don't have the

proper keys in place and doing a join where you are using different keys

combined with OR.  The MySQL benchmark suite at

@uref{http://www.mysql.com/information/benchmarks.html} shows you what

kind of constructs you should watch out for when using different

databases.

@item

PostgreSQL has a bigger team of developers that contribute to the server.

@end itemize

Drawbacks with PostgreSQL compared to MySQL:

@itemize @bullet

@item

@code{VACUUM()} makes PostgreSQL hard to use in a 24/7 environment.

@item

Only transactional tables.

@item

Much slower @code{INSERT}, @code{DELETE}, and @code{UPDATE}.

@end itemize

For a complete list of drawbacks, you should also examine the first table

in this section.

@node Installing, Tutorial, Introduction, Top

@chapter MySQL Installation