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<title>Overview</title>

<para>

This release adds major new capabilities to the

<productname>PostgreSQL</> database system, including:

This release adds many improvements that were requested by users,

including:

<itemizedlist>

<listitem>

<para>

Full text search now fully integrated into the core database

system

Full text search is now a built-in feature

</para>

</listitem>

<listitem>

<para>

Enumerated (enum) data types

enum data types

</para>

</listitem>

<listitem>

<para>

Universally Unique Identifier (UUID) data type, similar to that

defined by RFC 4122

UUID data type, similar to that defined by RFC 4122

</para>

</listitem>

<listitem>

<para>

Control of whether <literal>NULL</>s sort first or last, using

<literal>ORDER BY ... NULLS FIRST/LAST</>

</para>

</listitem>

<listitem>

<para>

Updatable cursors using <literal>UPDATE/DELETE WHERE CURRENT OF</>

<replaceable>cursor_name</>

Updatable cursors

(<literal>UPDATE/DELETE WHERE CURRENT OF</>

<replaceable>cursor_name</>)

</para>

</listitem>

<listitem>

<para>

Per-functionserver configurationparameter settings

Per-function parameter settings

</para>

</listitem>

<listitem>

<para>

User-defined types can now have type modifiers

User-defined types can now have type modifiers (parameters)

</para>

<para>

This allows a user type to take an optional modifier when

being created, e.g. <type>SSNUM(7)</>. Previously only

predefined system data types would allow this, e.g.

<type>CHAR(4)</>.

Declarations such as <type>varchar(42)</type> are no longer

restricted to use by built-in data types.

</para>

</listitem>

<listitem>

<para>

Numerous improvements in logging and statistics collection,

including the ability to emit postmaster log messages in

<acronym>CSV</> format, which can be loaded into a database

tablefor analysis

Numerous improvements in logging and statistics collection

capabilities,including the ability to emit postmaster log messages

inCSV format that can bedirectlyloaded into a database table

for analysis

</para>

</listitem>

</para>

<para>

This allows multiple vacuums to run concurrently, meaning

vacuuming of a large table will not prevent smaller tables from

being vacuumed at the same time. Autovacuum is now considered

mature and therefore is enabled by default.

Autovacuum is now considered mature enough to be enabled by default.

</para>

</listitem>

<listitem>

<para>

Thebackend database server can now be compiled with

<productname>Microsoft Visual C++</>

Theentire <productname>PostgreSQL</productname> system can

now be compiled withMicrosoft Visual C++

</para>

<para>

stability and performance than thosemade withother tool sets.

will also work.

contribute to the project. Windows executablesmade withVisual C++

other tool sets.

</para>

</listitem>

<listitem>

<para>

Asynchronous commit optionallowstransactions to becommitted

Asynchronous commit optionto allowtransactions to bereported

</para>

<para>

This feature dramatically increases performance for data

modification queries. The disadvantage is that because on-disk

changes are delayed, if the operating system crashes before data

is written to the disk, committed data will be lost. This is

only useful for applications that can accept some data loss.

Unlike <varname>fsync</varname>, asynchronous commit does not

risk database corruption; the worst case is that after an

operating system crash, the last few reportedly-committed

transactions will be missing.

This would not, of course, be acceptable if the client takes some

critical external action on the assumption that the transaction

will be remembered; but for certain applications, it is an acceptable

risk for some or all transactions to use this mode. Unlike existing

options such as <varname>fsync</varname>, asynchronous commit does

not risk database corruption; the worst case is that after a crash,

the last few reportedly-committed transactions will not have

taken effect.

</para>

</listitem>

<listitem>

<para>

<quote>Distributed</> checkpointspreventI/Ospikes during

<quote>Distributed</> checkpointsto spread out theI/Oload of a

</para>

</listitem>

<listitem>

<para>

Heap-Only Tuples (<acronym>HOT</>) reduce overhead of updates

</para>

<para>

To allow high concurrency <productname>PostgreSQL</> retains old

versions of updated rows. Previously only <command>VACUUM</>

could reuse space taken by dead rows. With <acronym>HOT</> dead

row space can be reused at the time of <command>UPDATE</> or

<command>INSERT</>. This allows for more consistent performance.

Heap-Only Tuples (HOT) to reduce overhead of updates

</para>

</listitem>

Just-in-time background writer strategy to improve disk write

efficiency

</para>

<para>

This basically makes the background writer self-tuning.

</para>

</listitem>

<listitem>

<para>

Reduction of both per-field and per-row storage requirements

</para>

<para>

For example, two <type>CHAR(1)</type> fields now take 4 bytes

instead of 16.

Reduction of on-disk data size through reducing both per-tuple

and per-field overheads

</para>

</listitem>