Add option SKIP_LOCKED to VACUUM and ANALYZE

When specified, this option allows VACUUM to skip the work on a relation
if there is a conflicting lock on it when trying to open it at the
beginning of its processing.

Similarly to autovacuum, this comes with a couple of limitations while
the relation is processed which can cause the process to still block:
- when opening the relation indexes.
- when acquiring row samples for table inheritance trees, partition trees
or certain types of foreign tables, and that a lock is taken on some
leaves of such trees.

Author: Nathan Bossart
Reviewed-by: Michael Paquier, Andres Freund, Masahiko Sawada
Discussion: https://postgr.es/m/9EF7EBE4-720D-4CF1-9D0E-4403D7E92990@amazon.com
Discussion: https://postgr.es/m/20171201160907.27110.74730@wrigleys.postgresql.org

2 files changed, 40 insertions, 0 deletions

diff --git a/doc/src/sgml/ref/analyze.sgml b/doc/src/sgml/ref/analyze.sgml
index 10b3a9a6733..fea7f465215 100644
--- a/doc/src/sgml/ref/analyze.sgml
+++ b/doc/src/sgml/ref/analyze.sgml
@@ -27,6 +27,7 @@ ANALYZE [ VERBOSE ] [ <replaceable class="parameter">table_and_columns</replacea
 <phrase>where <replaceable class="parameter">option</replaceable> can be one of:</phrase>
 
     VERBOSE
+    SKIP_LOCKED
 
 <phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>
 
@@ -77,6 +78,24 @@ ANALYZE [ VERBOSE ] [ <replaceable class="parameter">table_and_columns</replacea
    </varlistentry>
 
    <varlistentry>
+    <term><literal>SKIP_LOCKED</literal></term>
+    <listitem>
+     <para>
+      Specifies that <command>ANALYZE</command> should not wait for any
+      conflicting locks to be released when beginning work on a relation:
+      if a relation cannot be locked immediately without waiting, the relation
+      is skipped.  Note that even with this option, <command>ANALYZE</command>
+      may still block when opening the relation's indexes or when acquiring
+      sample rows from partitions, table inheritance children, and some
+      types of foreign tables.  Also, while <command>ANALYZE</command>
+      ordinarily processes all partitions of specified partitioned tables,
+      this option will cause <command>ANALYZE</command> to skip all
+      partitions if there is a conflicting lock on the partitioned table.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="parameter">table_name</replaceable></term>
     <listitem>
      <para>
diff --git a/doc/src/sgml/ref/vacuum.sgml b/doc/src/sgml/ref/vacuum.sgml
index b760e8ede18..fd911f57766 100644
--- a/doc/src/sgml/ref/vacuum.sgml
+++ b/doc/src/sgml/ref/vacuum.sgml
@@ -31,6 +31,7 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet
     VERBOSE
     ANALYZE
     DISABLE_PAGE_SKIPPING
+    SKIP_LOCKED
 
 <phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>
 
@@ -161,6 +162,26 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ <replaceable class="paramet
    </varlistentry>
 
    <varlistentry>
+    <term><literal>SKIP_LOCKED</literal></term>
+    <listitem>
+     <para>
+      Specifies that <command>VACUUM</command> should not wait for any
+      conflicting locks to be released when beginning work on a relation:
+      if a relation cannot be locked immediately without waiting, the relation
+      is skipped.  Note that even with this option,
+      <command>VACUUM</command> may still block when opening the relation's
+      indexes.  Additionally, <command>VACUUM ANALYZE</command> may still
+      block when acquiring sample rows from partitions, table inheritance
+      children, and some types of foreign tables.  Also, while
+      <command>VACUUM</command> ordinarily processes all partitions of
+      specified partitioned tables, this option will cause
+      <command>VACUUM</command> to skip all partitions if there is a
+      conflicting lock on the partitioned table.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="parameter">table_name</replaceable></term>
     <listitem>
      <para>