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Expose control file data via SQL accessible functions.
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Add four new SQL accessible functions: pg_control_system(),
pg_control_checkpoint(), pg_control_recovery(), and pg_control_init()
which expose a subset of the control file data.

Along the way move the code to read and validate the control file to
src/common, where it can be shared by the new backend functions
and the original pg_controldata frontend program.

Patch by me, significant input, testing, and review by Michael Paquier.
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@jconway
jconway committed Mar 5, 2016
1 parent d34794f commit dc7d70e
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356 changes: 356 additions & 0 deletions doc/src/sgml/func.sgml
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Expand Up @@ -16703,6 +16703,362 @@ SELECT collation for ('foo' COLLATE "de_DE");
</tgroup>
</table>

<para>
The functions shown in <xref linkend="functions-controldata">
print information initialized during <command>initdb</>, such
as the catalog version. They also show information about write-ahead
logging and checkpoint processing. This information is cluster-wide,
and not specific to any one database. They provide most of the same
information, from the same source, as
<xref linkend="APP-PGCONTROLDATA">, although in a form better suited
to <acronym>SQL</acronym> functions.
</para>

<table id="functions-controldata">
<title>Control Data Functions</title>
<tgroup cols="3">
<thead>
<row><entry>Name</entry> <entry>Return Type</entry> <entry>Description</entry></row>
</thead>

<tbody>
<row>
<entry>
<indexterm><primary>pg_control_checkpoint</primary></indexterm>
<literal><function>pg_control_checkpoint()</function></literal>
</entry>
<entry><type>record</type></entry>
<entry>
Returns information about current checkpoint state.
</entry>
</row>

<row>
<entry>
<indexterm><primary>pg_control_system</primary></indexterm>
<literal><function>pg_control_system()</function></literal>
</entry>
<entry><type>record</type></entry>
<entry>
Returns information about current controldata file state.
</entry>
</row>

<row>
<entry>
<indexterm><primary>pg_control_init</primary></indexterm>
<literal><function>pg_control_init()</function></literal>
</entry>
<entry><type>record</type></entry>
<entry>
Returns information about cluster initialization state.
</entry>
</row>

<row>
<entry>
<indexterm><primary>pg_control_recovery</primary></indexterm>
<literal><function>pg_control_recovery()</function></literal>
</entry>
<entry><type>record</type></entry>
<entry>
Returns information about recovery state.
</entry>
</row>

</tbody>
</tgroup>
</table>

<para>
<function>pg_control_checkpoint</> returns a record, shown in
<xref linkend="functions-pg-control-checkpoint">
</para>

<table id="functions-pg-control-checkpoint">
<title><function>pg_control_checkpoint</> Columns</title>
<tgroup cols="2">
<thead>
<row>
<entry>Column Name</entry>
<entry>Data Type</entry>
</row>
</thead>

<tbody>

<row>
<entry>checkpoint_location</entry>
<entry><type>pg_lsn</type></entry>
</row>

<row>
<entry>prior_location</entry>
<entry><type>pg_lsn</type></entry>
</row>

<row>
<entry>redo_location</entry>
<entry><type>pg_lsn</type></entry>
</row>

<row>
<entry>redo_wal_file</entry>
<entry><type>text</type></entry>
</row>

<row>
<entry>timeline_id</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>prev_timeline_id</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>full_page_writes</entry>
<entry><type>boolean</type></entry>
</row>

<row>
<entry>next_xid</entry>
<entry><type>text</type></entry>
</row>

<row>
<entry>next_oid</entry>
<entry><type>oid</type></entry>
</row>

<row>
<entry>next_multixact_id</entry>
<entry><type>xid</type></entry>
</row>

<row>
<entry>next_multi_offset</entry>
<entry><type>xid</type></entry>
</row>

<row>
<entry>oldest_xid</entry>
<entry><type>xid</type></entry>
</row>

<row>
<entry>oldest_xid_dbid</entry>
<entry><type>oid</type></entry>
</row>

<row>
<entry>oldest_active_xid</entry>
<entry><type>xid</type></entry>
</row>

<row>
<entry>oldest_multi_xid</entry>
<entry><type>xid</type></entry>
</row>

<row>
<entry>oldest_multi_dbid</entry>
<entry><type>oid</type></entry>
</row>

<row>
<entry>oldest_commit_ts_xid</entry>
<entry><type>xid</type></entry>
</row>

<row>
<entry>newest_commit_ts_xid</entry>
<entry><type>xid</type></entry>
</row>

<row>
<entry>checkpoint_time</entry>
<entry><type>timestamp with time zone</type></entry>
</row>

</tbody>
</tgroup>
</table>

<para>
<function>pg_control_system</> returns a record, shown in
<xref linkend="functions-pg-control-system">
</para>

<table id="functions-pg-control-system">
<title><function>pg_control_system</> Columns</title>
<tgroup cols="2">
<thead>
<row>
<entry>Column Name</entry>
<entry>Data Type</entry>
</row>
</thead>

<tbody>

<row>
<entry>pg_control_version</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>catalog_version_no</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>system_identifier</entry>
<entry><type>bigint</type></entry>
</row>

<row>
<entry>pg_control_last_modified</entry>
<entry><type>timestamp with time zone</type></entry>
</row>

</tbody>
</tgroup>
</table>

<para>
<function>pg_control_init</> returns a record, shown in
<xref linkend="functions-pg-control-init">
</para>

<table id="functions-pg-control-init">
<title><function>pg_control_init</> Columns</title>
<tgroup cols="2">
<thead>
<row>
<entry>Column Name</entry>
<entry>Data Type</entry>
</row>
</thead>

<tbody>

<row>
<entry>max_data_alignment</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>database_block_size</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>blocks_per_segment</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>wal_block_size</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>bytes_per_wal_segment</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>max_identifier_length</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>max_index_columns</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>max_toast_chunk_size</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>large_object_chunk_size</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>bigint_timestamps</entry>
<entry><type>boolean</type></entry>
</row>

<row>
<entry>float4_pass_by_value</entry>
<entry><type>boolean</type></entry>
</row>

<row>
<entry>float8_pass_by_value</entry>
<entry><type>boolean</type></entry>
</row>

<row>
<entry>data_page_checksum_version</entry>
<entry><type>integer</type></entry>
</row>

</tbody>
</tgroup>
</table>

<para>
<function>pg_control_recovery</> returns a record, shown in
<xref linkend="functions-pg-control-recovery">
</para>

<table id="functions-pg-control-recovery">
<title><function>pg_control_recovery</> Columns</title>
<tgroup cols="2">
<thead>
<row>
<entry>Column Name</entry>
<entry>Data Type</entry>
</row>
</thead>

<tbody>

<row>
<entry>min_recovery_end_location</entry>
<entry><type>pg_lsn</type></entry>
</row>

<row>
<entry>min_recovery_end_timeline</entry>
<entry><type>integer</type></entry>
</row>

<row>
<entry>backup_start_location</entry>
<entry><type>pg_lsn</type></entry>
</row>

<row>
<entry>backup_end_location</entry>
<entry><type>pg_lsn</type></entry>
</row>

<row>
<entry>end_of_backup_record_required</entry>
<entry><type>boolean</type></entry>
</row>

</tbody>
</tgroup>
</table>

</sect1>

<sect1 id="functions-admin">
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2 changes: 1 addition & 1 deletion src/backend/utils/misc/Makefile
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Expand Up @@ -14,7 +14,7 @@ include $(top_builddir)/src/Makefile.global

override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)

OBJS = guc.o help_config.o pg_config.o pg_rusage.o \
OBJS = guc.o help_config.o pg_config.o pg_controldata.o pg_rusage.o \
ps_status.o rls.o sampling.o superuser.o timeout.o tzparser.o

# This location might depend on the installation directories. Therefore
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