*** a/doc/src/sgml/config.sgml
--- b/doc/src/sgml/config.sgml
***************
*** 5622,5627 **** COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
--- 5622,5664 ----
        </listitem>
       </varlistentry>
  
+      <varlistentry id="guc-default-index-tablespace" xreflabel="default_index_tablespace">
+       <term><varname>default_index_tablespace</varname> (<type>string</type>)
+       <indexterm>
+        <primary><varname>default_index_tablespace</> configuration parameter</primary>
+       </indexterm>
+       <indexterm><primary>tablespace</><secondary>default</></>
+       </term>
+       <listitem>
+        <para>
+         This variable specifies the default tablespace in which to create
+         indexes when a <command>CREATE INDEX</> command does
+         not explicitly specify a tablespace.
+        </para>
+ 
+        <para>
+         The value is either the name of a tablespace, or an empty string
+         to specify using the default tablespace of the current database
+         unless the <xref linkend="guc-default-tablespace"> is defined,
+         in which case the rules for that parameter apply.
+         If the value does not match the name of any existing tablespace,
+         <productname>PostgreSQL</> will automatically use the default
+         tablespace of the current database; the user must have 
+         <literal>CREATE</> privilege for it, or creation attempts will fail.
+        </para>
+ 
+        <para>
+         This variable is not used for indexes on temporary tables; for them,
+         <xref linkend="guc-temp-tablespaces"> is consulted instead.
+        </para>
+ 
+        <para>
+         For more information on tablespaces,
+         see <xref linkend="manage-ag-tablespaces">.
+        </para>
+       </listitem>
+      </varlistentry>
+ 
       <varlistentry id="guc-temp-tablespaces" xreflabel="temp_tablespaces">
        <term><varname>temp_tablespaces</varname> (<type>string</type>)
        <indexterm>
*** a/src/backend/commands/indexcmds.c
--- b/src/backend/commands/indexcmds.c
***************
*** 417,423 **** DefineIndex(Oid relationId,
  	}
  	else
  	{
! 		tablespaceId = GetDefaultTablespace(rel->rd_rel->relpersistence);
  		/* note InvalidOid is OK in this case */
  	}
  
--- 417,423 ----
  	}
  	else
  	{
! 		tablespaceId = GetIndexTablespace(rel->rd_rel->relpersistence);
  		/* note InvalidOid is OK in this case */
  	}
  
*** a/src/backend/commands/tablespace.c
--- b/src/backend/commands/tablespace.c
***************
*** 86,91 ****
--- 86,92 ----
  
  /* GUC variables */
  char	   *default_tablespace = NULL;
+ char	   *default_index_tblspc = NULL;
  char	   *temp_tablespaces = NULL;
  
  
***************
*** 1085,1090 **** GetDefaultTablespace(char relpersistence)
--- 1086,1149 ----
  
  
  /*
+  * GetIndexTablespace -- get the OID of the tablespace for an index
+  *
+  * Temporary objects have different default tablespaces, hence the
+  * relpersistence parameter must be specified.
+  *
+  * May return InvalidOid to indicate "use the database's default tablespace".
+  *
+  * Note that caller is expected to check appropriate permissions for any
+  * result other than InvalidOid.
+  *
+  * This exists to hide (and possibly optimize the use of) the
+  * default_index_tablespace GUC variable.
+  */
+ Oid
+ GetIndexTablespace(char relpersistence)
+ {
+ 	Oid			result;
+ 	const char	       *tablespace;
+ 
+ 	/* The temp-table case is handled elsewhere */
+ 	if (relpersistence == RELPERSISTENCE_TEMP)
+ 	{
+ 		PrepareTempTablespaces();
+ 		return GetNextTempTableSpace();
+ 	}
+ 
+ 	/* Fast path for empty GUC: check defaults */
+ 	if (default_index_tblspc == NULL || default_index_tblspc[0] == '\0')
+ 	{
+ 	        /* if default_tablespace is also empty, return immediately */
+ 	        if (default_tablespace == NULL || default_tablespace[0] == '\0')
+ 		        return InvalidOid;
+                 else
+                         tablespace = default_tablespace;
+ 	}
+ 	else
+ 	        tablespace = default_index_tblspc;
+ 
+ 	/*
+ 	 * It is tempting to cache this lookup for more speed, but then we would
+ 	 * fail to detect the case where the tablespace was dropped since the GUC
+ 	 * variable was set.  Note also that we don't complain if the value fails
+ 	 * to refer to an existing tablespace; we just silently return InvalidOid,
+ 	 * causing the new object to be created in the database's tablespace.
+ 	 */
+ 	result = get_tablespace_oid(tablespace, true);
+ 
+ 	/*
+ 	 * Allow explicit specification of database's default tablespace in
+ 	 * default_tablespace without triggering permissions checks.
+ 	 */
+ 	if (result == MyDatabaseTableSpace)
+ 		result = InvalidOid;
+ 	return result;
+ }
+ 
+ 
+ /*
   * Routines for handling the GUC variable 'temp_tablespaces'.
   */
  
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
***************
*** 109,114 **** extern int	CommitDelay;
--- 109,115 ----
  extern int	CommitSiblings;
  extern char *default_tablespace;
  extern char *temp_tablespaces;
+ extern char *default_index_tblspc;
  extern bool ignore_checksum_failure;
  extern bool synchronize_seqscans;
  
***************
*** 2894,2899 **** static struct config_string ConfigureNamesString[] =
--- 2895,2911 ----
  	},
  
  	{
+ 		{"default_index_tablespace", PGC_USERSET, CLIENT_CONN_STATEMENT,
+ 			gettext_noop("Sets the default tablespace to create indexes in."),
+ 			gettext_noop("An empty string selects the database's default tablespace."),
+ 			GUC_IS_NAME
+ 		},
+ 		&default_index_tblspc,
+ 		"",
+ 		check_default_tablespace, NULL, NULL
+ 	},
+ 
+ 	{
  		{"temp_tablespaces", PGC_USERSET, CLIENT_CONN_STATEMENT,
  			gettext_noop("Sets the tablespace(s) to use for temporary tables and sort files."),
  			NULL,
*** a/src/include/commands/tablespace.h
--- b/src/include/commands/tablespace.h
***************
*** 49,54 **** extern Oid	AlterTableSpaceOptions(AlterTableSpaceOptionsStmt *stmt);
--- 49,55 ----
  extern void TablespaceCreateDbspace(Oid spcNode, Oid dbNode, bool isRedo);
  
  extern Oid	GetDefaultTablespace(char relpersistence);
+ extern Oid	GetIndexTablespace(char relpersistence);
  
  extern void PrepareTempTablespaces(void);