postgres
diff --git a/‎doc/src/sgml/indexam.sgml
Lines changed: 9 additions & 1 deletion b/‎doc/src/sgml/indexam.sgml
Lines changed: 9 additions & 1 deletion
diff --git a/‎doc/src/sgml/monitoring.sgml
Lines changed: 13 additions & 0 deletions b/‎doc/src/sgml/monitoring.sgml
Lines changed: 13 additions & 0 deletions
diff --git a/‎src/backend/access/index/indexam.c
Lines changed: 4 additions & 6 deletions b/‎src/backend/access/index/indexam.c
Lines changed: 4 additions & 6 deletions
@@ -809,14 +809,22 @@ amrestrpos (IndexScanDesc scan);
   <para>
 <programlisting>
 Size
-amestimateparallelscan (void);
+amestimateparallelscan (int nkeys,
+                        int norderbys);
 </programlisting>
    Estimate and return the number of bytes of dynamic shared memory which
    the access method will be needed to perform a parallel scan.  (This number
    is in addition to, not in lieu of, the amount of space needed for
    AM-independent data in <structname>ParallelIndexScanDescData</structname>.)
   </para>
 
+  <para>
+   The <literal>nkeys</literal> and <literal>norderbys</literal>
+   parameters indicate the number of quals and ordering operators that will be
+   used in the scan; the same values will be passed to <function>amrescan</function>.
+   Note that the actual values of the scan keys aren't provided yet.
+  </para>
+
   <para>
    It is not necessary to implement this function for access methods which
    do not support parallel scans or for which the number of additional bytes
 
@@ -4064,6 +4064,19 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </para>
   </note>
 
+  <note>
+   <para>
+    Queries that use certain <acronym>SQL</acronym> constructs to search for
+    rows matching any value out of a list or array of multiple scalar values
+    (see <xref linkend="functions-comparisons"/>) perform multiple
+    <quote>primitive</quote> index scans (up to one primitive scan per scalar
+    value) during query execution.  Each internal primitive index scan
+    increments <structname>pg_stat_all_indexes</structname>.<structfield>idx_scan</structfield>,
+    so it's possible for the count of index scans to significantly exceed the
+    total number of index scan executor node executions.
+   </para>
+  </note>
+
  </sect2>
 
  <sect2 id="monitoring-pg-statio-all-tables-view">
 
@@ -449,13 +449,10 @@ index_restrpos(IndexScanDesc scan)
 
 /*
  * index_parallelscan_estimate - estimate shared memory for parallel scan
- *
- * Currently, we don't pass any information to the AM-specific estimator,
- * so it can probably only return a constant.  In the future, we might need
- * to pass more information.
  */
 Size
-index_parallelscan_estimate(Relation indexRelation, Snapshot snapshot)
+index_parallelscan_estimate(Relation indexRelation, int nkeys, int norderbys,
+							Snapshot snapshot)
 {
 	Size		nbytes;
 
@@ -474,7 +471,8 @@ index_parallelscan_estimate(Relation indexRelation, Snapshot snapshot)
 	 */
 	if (indexRelation->rd_indam->amestimateparallelscan != NULL)
 		nbytes = add_size(nbytes,
-						  indexRelation->rd_indam->amestimateparallelscan());
+						  indexRelation->rd_indam->amestimateparallelscan(nkeys,
+																		  norderbys));
 
 	return nbytes;
 }