Add DROP INDEX CONCURRENTLY [IF EXISTS], uses ShareUpdateExclusiveLock

1 files changed, 24 insertions, 1 deletions

diff --git a/doc/src/sgml/ref/drop_index.sgml b/doc/src/sgml/ref/drop_index.sgml
index 7177ef2d81b..343f7aca003 100644
--- a/doc/src/sgml/ref/drop_index.sgml
+++ b/doc/src/sgml/ref/drop_index.sgml
@@ -21,7 +21,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP INDEX [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
+DROP INDEX [ CONCURRENTLY ] [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ...] [ CASCADE | RESTRICT ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -50,6 +50,29 @@ DROP INDEX [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> [, ..
    </varlistentry>
 
    <varlistentry>
+    <term><literal>CONCURRENTLY</literal></term>
+    <listitem>
+     <para>
+      When this option is used, <productname>PostgreSQL</> will drop the
+      index without taking any locks that prevent concurrent selects, inserts,
+      updates, or deletes on the table; whereas a standard index drop
+      waits for a lock that locks out everything on the table until it's done.
+      Concurrent drop index is a two stage process. First, we mark the index
+      both invalid and not ready then commit the change. Next we wait until
+      there are no users locking the table who can see the index.
+     </para>
+     <para>
+      There are several caveats to be aware of when using this option.
+      Only one index name can be specified if the <literal>CONCURRENTLY</literal>
+      parameter is specified.  Regular <command>DROP INDEX</> command can be
+      performed within a transaction block, but
+      <command>DROP INDEX CONCURRENTLY</> cannot.
+      The CASCADE option is not supported when dropping an index concurrently.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>
      <para>