diff --git a/doc/src/sgml/spi.sgml b/doc/src/sgml/spi.sgml
index ea6bfc2a3f5..5232e001b8a 100644
--- a/doc/src/sgml/spi.sgml
+++ b/doc/src/sgml/spi.sgml
@@ -316,20 +316,32 @@ int SPI_execute(const char * <parameter>command</parameter>, bool <parameter>rea
   <para>
    If <parameter>count</parameter> is zero then the command is executed
    for all rows that it applies to.  If <parameter>count</parameter>
-   is greater than 0, then the number of rows for which the command
-   will be executed is restricted (much like a
-   <literal>LIMIT</literal> clause). For example:
+   is greater than zero, then no more than <parameter>count</parameter> rows
+   will be retrieved; execution stops when the count is reached, much like
+   adding a <literal>LIMIT</literal> clause to the query. For example,
+<programlisting>
+SPI_execute("SELECT * FROM foo", true, 5);
+</programlisting>
+   will retrieve at most 5 rows from the table.  Note that such a limit
+   is only effective when the command actually returns rows.  For example,
 <programlisting>
 SPI_execute("INSERT INTO foo SELECT * FROM bar", false, 5);
 </programlisting>
-   will allow at most 5 rows to be inserted into the table.
+   inserts all rows from <structname>bar</>, ignoring the
+   <parameter>count</parameter> parameter.  However, with
+<programlisting>
+SPI_execute("INSERT INTO foo SELECT * FROM bar RETURNING *", false, 5);
+</programlisting>
+   at most 5 rows would be inserted, since execution would stop after the
+   fifth <literal>RETURNING</> result row is retrieved.
   </para>
 
   <para>
    You can pass multiple commands in one string;
    <function>SPI_execute</function> returns the
    result for the command executed last.  The <parameter>count</parameter>
-   limit applies to each command separately, but it is not applied to
+   limit applies to each command separately (even though only the last
+   result will actually be returned).  The limit is not applied to any
    hidden commands generated by rules.
   </para>
 
@@ -431,7 +443,7 @@ typedef struct
     <term><literal>long <parameter>count</parameter></literal></term>
     <listitem>
      <para>
-      maximum number of rows to process or return,
+      maximum number of rows to return,
       or <literal>0</> for no limit
      </para>
     </listitem>
@@ -608,15 +620,12 @@ typedef struct
   <title>Notes</title>
 
   <para>
-   The functions <function>SPI_execute</function>,
-   <function>SPI_exec</function>,
-   <function>SPI_execute_plan</function>, and
-   <function>SPI_execp</function> change both
+   All SPI query-execution functions set both
    <varname>SPI_processed</varname> and
    <varname>SPI_tuptable</varname> (just the pointer, not the contents
    of the structure).  Save these two global variables into local
    procedure variables if you need to access the result table of
-   <function>SPI_execute</function> or a related function
+   <function>SPI_execute</function> or another query-execution function
    across later calls.
   </para>
  </refsect1>
@@ -671,7 +680,7 @@ int SPI_exec(const char * <parameter>command</parameter>, long <parameter>count<
     <term><literal>long <parameter>count</parameter></literal></term>
     <listitem>
      <para>
-      maximum number of rows to process or return,
+      maximum number of rows to return,
       or <literal>0</> for no limit
      </para>
     </listitem>
@@ -810,7 +819,7 @@ int SPI_execute_with_args(const char *<parameter>command</parameter>,
     <term><literal>long <parameter>count</parameter></literal></term>
     <listitem>
      <para>
-      maximum number of rows to process or return,
+      maximum number of rows to return,
       or <literal>0</> for no limit
      </para>
     </listitem>
@@ -1454,7 +1463,7 @@ int SPI_execute_plan(SPIPlanPtr <parameter>plan</parameter>, Datum * <parameter>
     <term><literal>long <parameter>count</parameter></literal></term>
     <listitem>
      <para>
-      maximum number of rows to process or return,
+      maximum number of rows to return,
       or <literal>0</> for no limit
      </para>
     </listitem>
@@ -1572,7 +1581,7 @@ int SPI_execute_plan_with_paramlist(SPIPlanPtr <parameter>plan</parameter>,
     <term><literal>long <parameter>count</parameter></literal></term>
     <listitem>
      <para>
-      maximum number of rows to process or return,
+      maximum number of rows to return,
       or <literal>0</> for no limit
      </para>
     </listitem>
@@ -1673,7 +1682,7 @@ int SPI_execp(SPIPlanPtr <parameter>plan</parameter>, Datum * <parameter>values<
     <term><literal>long <parameter>count</parameter></literal></term>
     <listitem>
      <para>
-      maximum number of rows to process or return,
+      maximum number of rows to return,
       or <literal>0</> for no limit
      </para>
     </listitem>
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 440438b1807..56be2a78d81 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -226,7 +226,9 @@ standard_ExecutorStart(QueryDesc *queryDesc, int eflags)
  *		we retrieve up to 'count' tuples in the specified direction.
  *
  *		Note: count = 0 is interpreted as no portal limit, i.e., run to
- *		completion.
+ *		completion.  Also note that the count limit is only applied to
+ *		retrieved tuples, not for instance to those inserted/updated/deleted
+ *		by a ModifyTable plan node.
  *
  *		There is no return value, but output tuples (if any) are sent to
  *		the destination receiver specified in the QueryDesc; and the number
@@ -1348,7 +1350,7 @@ ExecEndPlan(PlanState *planstate, EState *estate)
 /* ----------------------------------------------------------------
  *		ExecutePlan
  *
- *		Processes the query plan until we have processed 'numberTuples' tuples,
+ *		Processes the query plan until we have retrieved 'numberTuples' tuples,
  *		moving in the specified direction.
  *
  *		Runs to completion if numberTuples is 0