The process for an exclusive backup is mostly the same as for a

non-exclusive one, but it differs in a few key steps. This type of

backup can only be taken on a primary and does not allow concurrent

backups. Moreover, because itwrites abackup_labelfile on the

master, it cancause the master to fail to restart automatically after

a crash. On the other hand, the erroneous removal ofa backup_label

file from a backup or standby is a common mistake which can result

backups. Moreover, because itcreates abackup labelfile, as

described below, it canblock automatic restart of the master server

aftera crash. On the other hand, the erroneous removal ofthis

file from a backup or standby is a common mistake, which can result

in serious data corruption. If it is necessary to use this method,

the following steps may be used.

</para>

</para>

<para>

As noted above, if the server crashes during the backup it may not be

possible to restart until the <literal>backup_label</literal> file has

possible to restart until the <filename>backup_label</filename> file has

been manually deleted from the <envar>PGDATA</envar> directory. Note

that it is very important to never remove the

<literal>backup_label</literal> file when restoring a backup, because

<filename>backup_label</filename> file when restoring a backup, because

this will result in corruption. Confusion about when it is appropriate

to remove this file is a common cause of data corruption when using this

method; be very certain that you remove the file only on an existing

lack of disk space, failure to call <function>pg_stop_backup</function>

will leave the server in backup mode indefinitely, causing future backups

to fail and increasing the risk of a restart failure during the time that

<literal>backup_label</literal> exists.

<filename>backup_label</filename> exists.

</para>

</listitem>

</orderedlist>

</biblioentry>

<biblioentry id="sqltr-19075-6">

<title>SQL Technical Report</title>

<title><ulink url="http://standards.iso.org/ittf/PubliclyAvailableStandards/c067367_ISO_IEC_TR_19075-6_2017.zip">SQL Technical Report</ulink></title>

<subtitle>Part 6: SQL support for JavaScript Object

Notation (JSON)</subtitle>

<edition>First Edition.</edition>

<biblioid>

<ulink url="http://standards.iso.org/ittf/PubliclyAvailableStandards/c067367_ISO_IEC_TR_19075-6_2017.zip"></ulink>.

</biblioid>

<pubdate>2017.</pubdate>

<edition>First Edition</edition>

<pubdate>2017</pubdate>

</biblioentry>

</bibliodiv>

<listitem>

<para>

Backward compatibility syntax for removing the <literal>oid</literal>

system column. As oid system columns cannot be added anymore, this never

has an effect.

system column. As<literal>oid</literal> system columns cannot be added

anymore, this neverhas an effect.

</para>

</listitem>

</varlistentry>

to be written safely to disk. This option causes

<command>pg_checksums</command> to return without waiting, which is

faster, but means that a subsequent operating system crash can leave

the updated datafolder corrupt. Generally, this option is useful

the updated datadirectory corrupt. Generally, this option is useful

for testing but should not be used on a production installation.

This option has no effect when using <literal>--check</literal>.

</para>

<term><option>--extra-float-digits=<replaceable class="parameter">ndigits</replaceable></option></term>

<listitem>

<para>

Use the specified value of extra_float_digits when dumping

Use the specified value of<option>extra_float_digits</option> when dumping

floating-point data, instead of the maximum available precision.

Routine dumps made for backup purposes should not use this option.

</para>

to be written safely to disk. This option causes

<command>pg_rewind</command> to return without waiting, which is

faster, but means that a subsequent operating system crash can leave

the synchronized datafolder corrupt. Generally, this option is

the synchronized datadirectory corrupt. Generally, this option is

useful for testing but should not be used when creating a production

installation.

</para>

</listitem>

</itemizedlist>

Because in "prepared" mode <application>pgbench</application> reuses

the parse analysis resultforthe second and subsequent query

iteration, <application>pgbench</application> runs faster in the

prepared modethan in other modes.

In the <literal>prepared</literal> mode, <application>pgbench</application>

reusesthe parse analysis resultstarting fromthe second query

iteration,so<application>pgbench</application> runs faster

than in other modes.

</para>

<para>

The default is simple query protocol. (See <xref linkend="protocol"/>

<para>

When this option is used, <productname>PostgreSQL</productname> will rebuild the

index without taking any locks that prevent concurrent inserts,

updates, or deletes on the table; whereas a standardreindex build

updates, or deletes on the table; whereas a standardindex rebuild

locks out writes (but not reads) on the table until it's done.

There are several caveats to be aware of when using this option

&mdash; see <xref linkend="sql-reindex-concurrently"

of writes. This method is invoked by specifying the

<literal>CONCURRENTLY</literal> option of <command>REINDEX</command>. When this option

is used, <productname>PostgreSQL</productname> must perform two scans of the table

for each index that needs to berebuild andin addition it mustwait for

all existing transactions that could potentially use the index to

terminate.This method requires more total work than a standard index

for each index that needs to berebuilt and wait for termination of

all existing transactions that could potentially use the index.

This method requires more total work than a standard index

rebuild and takes significantly longer to complete as it needs to wait

for unfinished transactions that might modify the index. However, since

it allows normal operations to continue while the index is rebuilt, this

it allows normal operations to continue while the index isbeingrebuilt, this

method is useful for rebuilding indexes in a production environment. Of

course, the extra CPU, memory and I/O load imposed by the index rebuild

may slow down other operations.

</programlisting></para>

<para>

Rebuild a table while authorizing read and write operations on involved

relationswhen performed:

Rebuildindexes fora table, without blocking read and write operations

on involvedrelationswhile reindexing is in progress:

<programlisting>

REINDEX TABLE CONCURRENTLY my_broken_table;