<Sect1>

<Title>A Short History of <ProductName>Postgres</ProductName></Title>

<Para>

The Object-Relational Database Management System now known as

<ProductName>PostgreSQL</ProductName> was originally called

<ProductName>Postgres</ProductName>, and briefly called

<ProductName>Postgres95</ProductName>. With over a decade of

development behind it, <ProductName>PostgreSQL</ProductName>

is the most advanced open-source database available anywhere,

offering multi-version concurrency control and supporting almost

all SQL constructs, including subselects, transactions, and

user-defined types and functions.

</Para>

<Sect2>

<Title>The Berkeley <ProductName>Postgres</ProductName> Project</Title>

Version 3 appeared in 1991 and added support for multiple

storage managers, an improved query executor, and a

rewritten rewrite rule system. For the most part,

releasessince then have focused on portability and

reliability.

releasesuntil <ProductName>Postgres95</ProductName> (see below)

focused on portability andreliability.

</Para>

<Para>

ended with Version 4.2.

</Para>

</Sect2>

<Sect2>

<Title><ProductName>Postgres95</ProductName></Title>

<ULink url="mailto:ayu@informix.com">Andrew Yu</ULink>

and

<ULink url="http://http.cs.berkeley.edu/~jolly/">Jolly Chen</ULink>

added a SQL language interpreter to <ProductName>Postgres</ProductName>,

and the code was subsequently released to

the Web to find its own way in the world.

<ProductName>Postgres95</ProductName> was a public-domain, open source descendant

of this originalBerkeley code.

added a SQL language interpreter to <ProductName>Postgres</ProductName>.

<ProductName>Postgres95</ProductName> was subsequently released to

the Web to find its own way in the world as a public-domain,

open source descendant of the original<ProductName>Postgres</ProductName>

Berkeley code.

</Para>

<Para>

<ProductName>Postgres95</ProductName> is a derivative of the last official release

of <ProductName>Postgres</ProductName> (version 4.2). The code is now completely

ANSI C and the code size has been trimmed by 25%. There

are a lot of internal changes that improve performance

and code maintainability.

<ProductName>Postgres95</ProductName> v1.0.x runs about 30-50%

faster on the Wisconsin Benchmark compared to v4.2.

Apart from bug fixes, these are the major enhancements:

<ProductName>Postgres95</ProductName> code was completely

ANSI C and trimmed in size by 25%. Many

internal changes improved performance and maintainability.

<ProductName>Postgres95</ProductName> v1.0.x ran about 30-50%

faster on the Wisconsin Benchmark compared to

<ProductName>Postgres</ProductName> v4.2.

Apart from bug fixes, these were the major enhancements:

<ItemizedList>

<ListItem>

<Para>

The query language <ProductName>Postquel</ProductName>has been replaced with

<Acronym>SQL</Acronym> (implemented in the server).We donotyet support

subqueries (which canbe imitated with userdefined

<Acronym>SQL</Acronym> functions). Aggregates have been

re-implemented.We also added supportfor ``GROUP BY''.

The <FileName>libpq</FileName> interfaceis still available for <Acronym>C</Acronym>

The query language <ProductName>Postquel</ProductName>was replaced with

<Acronym>SQL</Acronym> (implemented in the server).Subqueries werenotsupported until <ProductName>PostgreSQL</ProductName> (see below), but they

couldbe imitatedin <ProductName>Postgres95</ProductName>with user-defined

<Acronym>SQL</Acronym> functions. Aggregateswere

re-implemented.Supportfor ``GROUP BY'' was also added.

The <FileName>libpq</FileName> interfaceremained available for <Acronym>C</Acronym>

programs.

</Para>

</ListItem>

<ListItem>

<Para>

In addition to the monitor program, we provide a new

program (<Application>psql</Application>) which supports <Acronym>GNU</Acronym> <FileName>readline</FileName>.

In addition to the monitor program, a new program

(<Application>psql</Application>) was provided for interactive SQL queries

using <Acronym>GNU</Acronym> <FileName>readline</FileName>.

</Para>

</ListItem>

<ListItem>

<Para>

We added anew front-end library, <FileName>libpgtcl</FileName>, that

supports <Acronym>Tcl</Acronym>-based clients. A sample shell,

pgtclsh,provides new Tcl commands to interface <Application>tcl</Application>

Anew front-end library, <FileName>libpgtcl</FileName>,

supported <Acronym>Tcl</Acronym>-based clients. A sample shell,

pgtclsh,provided new Tcl commands to interface <Application>tcl</Application>

programs with the <ProductName>Postgres95</ProductName> backend.

</Para>

</ListItem>

<ListItem>

<Para>

The large object interface has been overhauled. We

kept Inversion large objects as the only mechanism

for storing large objects. (This is not to be

confused with the Inversion file system which has been

removed.)

The large object interface was overhauled. The Inversion large objects were

the only mechanism for storing large objects.

(The Inversion file system was removed.)

</Para>

</ListItem>

<ListItem>

<Para>

The instance-level rule systemhas been removed.

Rulesare still available as rewrite rules.

The instance-level rule systemwas removed.

Ruleswere still available as rewrite rules.

</Para>

</ListItem>

<ListItem>

<Para>

A short tutorial introducing regular <Acronym>SQL</Acronym> features as

well as those ofours is distributed with the source

code.

well as those of<ProductName>Postgres95</ProductName> was

distributed with the sourcecode.

</Para>

</ListItem>

<ListItem>

<Para>

<Acronym>GNU</Acronym> make (instead of <Acronym>BSD</Acronym> make)is used for the

build. Also, <ProductName>Postgres95</ProductName>can be compiled with an

unpatched <ProductName>gcc</ProductName> (data alignment of doubles has been

fixed).

<Acronym>GNU</Acronym> make (instead of <Acronym>BSD</Acronym> make)was used

for thebuild. Also, <ProductName>Postgres95</ProductName>could be

compiled with anunpatched <ProductName>gcc</ProductName>

(data alignment of doubles wasfixed).

</Para>

</ListItem>

</ItemizedList>

<Title><ProductName>PostgreSQL</ProductName></Title>

<Para>

By 1996, it became clear that the name <Quote>Postgres95</Quote> would not stand

the test of time. A new name, <ProductName>PostgreSQL</ProductName>,

was chosen to reflect the

relationship between original <ProductName>Postgres</ProductName>

and the more recent

versions with <Acronym>SQL</Acronym> capability.

At the same time, the version numbering

was reset to start at 6.0,

putting the numbers back into the sequence originally begun by

the <ProductName>Postgres</ProductName> Project.

By 1996, it became clear that the name <Quote>Postgres95</Quote> would

not stand the test of time. We chose a new name,

<ProductName>PostgreSQL</ProductName>, to reflect the relationship

between the original <ProductName>Postgres</ProductName> and the more

recent versions with <Acronym>SQL</Acronym> capability. At the same

time, we set the version numbering to start at 6.0, putting the

numbers back into the sequence originally begun by the

<ProductName>Postgres</ProductName> Project.

</Para>

<Para>

The emphasis on development for the v1.0.x releases of

<ProductName>Postgres95</ProductName>

was on stabilizing the backend code.

With the v6.x series of <ProductName>PostgreSQL</ProductName>,

the emphasis has shifted from

identifying and understanding existing problems in the backend

to augmenting features and capabilities, although

The emphasis during development of <ProductName>Postgres95</ProductName>

was on identifying and understanding existing problems in the backend code.

With <ProductName>PostgreSQL</ProductName>,

the emphasis has shifted to augmenting features and capabilities, although

work continues in all areas.

</Para>

<Para>

Major enhancements include:

Major enhancementsin <ProductName>PostgreSQL</ProductName>include:

</Para>

<ItemizedList>

<ListItem>

<Para>

Table-level locking has been replaced with multi-version concurrency control,

which allows readers to continue reading consistent data during writer activity

and enables hot backups from pg_dump while the database stays available for

queries.

</Para>

</ListItem>

<ListItem>

<Para>

Important backend features, including subselects, defaults,

constraints, and triggers, have been implemented.

</Para>