docs: optimizer_join_order guc (#4014)

* docs: optimizer_join_order guc

* Implement suggested edits

* Note iteractions with other params; correct inaccurate statement.

* Clarify this is a GPORCA guc

gpdb-doc/dita/admin_guide/query/topics/query-piv-opt-notes.xml

@@ -29,6 +29,8 @@
         aggregate plan for a scalar distinct qualified aggregate. </li>
       <li><codeph>optimizer_force_three_stage_scalar_dqa</codeph> forces GPORCA to choose a plan
         with multistage aggregates when such a plan alternative is generated. </li>
+      <li><codeph>optimizer_join_order</codeph> sets the query optimization level for join ordering
+        by specifying which types of join ordering alternatives to evaluate.</li>
       <li><codeph>optimizer_join_order_threshold</codeph> specifies the maximum number of join
         children for which GPORCA uses the dynamic programming-based join ordering algorithm.</li>
       <li><codeph>optimizer_nestloop_factor</codeph> controls nested loop join cost factor to apply
@@ -52,7 +54,8 @@
     <p> For information about the parameters, see the <cite>Greenplum Database Reference
         Guide</cite>.</p>
     <p>GPORCA generates minidumps to describe the optimization context for a given query. <ph
-        otherprops="pivotal">The minidump files are used by Pivotal support to analyze Greenplum
+        otherprops="pivotal"
+        >The minidump files are used by Pivotal support to analyze Greenplum
         Database issues. </ph>The information in the file is not in a format that can be easily used
       for debugging or troubleshooting. The minidump file is located under the master data directory
       and uses the following naming format:</p>

gpdb-doc/dita/admin_guide/topics/gporca-parameters.xml

@@ -18,6 +18,7 @@
             </stentry>
             <stentry>
                <p><codeph>optimizer_join_arity_for_associativity_commutativity</codeph></p>
+               <p><codeph>optimizer_join_order</codeph></p>
                <p><codeph>optimizer_join_order_threshold</codeph></p>
                <p><codeph>optimizer_mdcache_size</codeph>
                </p>

gpdb-doc/dita/ref_guide/config_params/guc-list.xml

@@ -676,6 +676,9 @@
             <li><xref href="#optimizer_join_arity_for_associativity_commutativity" type="section"
                 >optimizer_join_arity_for_associativity_commutativity</xref>
             </li>
+            <li>
+              <xref href="#optimizer_join_order" type="section">optimizer_join_order</xref>
+            </li>
             <li>
               <xref href="#optimizer_join_order_threshold" type="section"
                 >optimizer_join_order_threshold</xref>
@@ -7689,13 +7692,15 @@
       <p>The value is an optimization hint to limit the number of join associativity and join
         commutativity transformations explored during query optimization. The limit controls the
         alternative plans that GPORCA considers during query optimization. For example, the default
-        value of 7 is a optimization hint for GPORCA to stop exploring join associativity and join
+        value of 7 is an optimization hint for GPORCA to stop exploring join associativity and join
         commutativity transformations when an n-ary join operator has more than 7 children during
         optimization.</p>
       <p>For a query with a large number of joins, specifying a lower value improves query
         performance by limiting the number of alternate query plans that GPORCA evaluates. However,
         setting the value too low might cause GPORCA to generate a query plan that performs
         sub-optimally.</p>
+      <p>This parameter has no effect when the <codeph>optimizer_join_order</codeph> parameter is 
+        set to <codeph>query</codeph> or <codeph>greedy</codeph>.</p>
       <p>This parameter can be set for a database system or a session.</p>
       <table id="table_lfq_3zg_nbb">
         <tgroup cols="3">
@@ -7720,13 +7725,61 @@
       </table>
     </body>
   </topic>
+  <topic id="optimizer_join_order">
+    <title>optimizer_join_order</title>
+    <body>
+      <p>When GPORCA is enabled, this parameter sets the optimization level for join 
+        ordering during query optimization by specifying which types of join ordering 
+        alternatives to evaluate.</p>
+      <ul id="ul_dpf_cyr_1cb">
+        <li><codeph>query</codeph> - Uses the join order specified in the query.</li>
+        <li><codeph>greedy</codeph> - Evaluates the join order specified in the query and 
+          alternatives based on minimum cardinalities of the relations in the joins.</li>
+        <li><codeph>exhaustive</codeph> - Applies transformation rules to find and evaluate 
+          all join ordering alternatives.</li>
+      </ul>
+      <p>The default value is <codeph>exhaustive</codeph>. Setting this parameter to 
+        <codeph>query</codeph> or <codeph>greedy</codeph> can generate a suboptimal 
+        query plan. However, if the administrator is confident that a satisfactory plan 
+        is generated with the <codeph>query</codeph> or <codeph>greedy</codeph> setting, 
+        query optimization time can be improved by setting the parameter to the lower 
+        optimization level.</p>
+      <p>Setting this parameter to <codeph>query</codeph> or <codeph>greedy</codeph> 
+        overrides the <codeph>optimizer_join_order_threshold </codeph> and 
+        <codeph>optimizer_join_arity_for_associativity_commutativity</codeph> parameters. </p>
+      <p>This parameter can be set for an individual database, a session, or a query. </p>
+      <table id="table_ucb_str_1cb">
+        <tgroup cols="3">
+          <colspec colnum="1" colname="col1" colwidth="1*"/>
+          <colspec colnum="2" colname="col2" colwidth="1*"/>
+          <colspec colnum="3" colname="col3" colwidth="1*"/>
+          <thead>
+            <row>
+              <entry colname="col1">Value Range</entry>
+              <entry colname="col2">Default</entry>
+              <entry colname="col3">Set Classifications</entry>
+            </row>
+          </thead>
+          <tbody>
+            <row>
+              <entry colname="col1">query<p>greedy</p><p>exhaustive</p></entry>
+              <entry colname="col2">exhaustive</entry>
+              <entry colname="col3">master<p>session</p><p>reload</p></entry>
+            </row>
+          </tbody>
+        </tgroup>
+      </table>
+    </body>
+  </topic>
   <topic id="optimizer_join_order_threshold">
     <title>optimizer_join_order_threshold</title>
     <body>
       <p>When GPORCA is enabled (the default), this parameter sets the maximum number of join
         children for which GPORCA will use the dynamic programming-based join ordering algorithm.
         You can set this value for a single query or for an entire session.</p>
-      <table id="table_z1c_bqp_jx">
+      <p>This parameter has no effect when the <codeph>optimizer_join_query</codeph> parameter is 
+        set to <codeph>query</codeph> or <codeph>greedy</codeph>.</p>
+       <table id="table_z1c_bqp_jx">
         <tgroup cols="3">
           <colspec colnum="1" colname="col1" colwidth="1*"/>
           <colspec colnum="2" colname="col2" colwidth="1*"/>

gpdb-doc/dita/ref_guide/config_params/guc_category-list.xml

@@ -359,6 +359,8 @@
           <stentry>
             <p><xref href="guc-list.xml#optimizer_join_arity_for_associativity_commutativity"
                 type="section">optimizer_join_arity_for_associativity_commutativity</xref></p>
+            <p><xref href="guc-list.xml#optimizer_join_order" format="dita" type="section"
+                >optimizer_join_order</xref></p>
             <p><xref href="guc-list.xml#optimizer_join_order_threshold" format="dita"
                 >optimizer_join_order_threshold</xref></p>
             <p><xref href="guc-list.xml#optimizer_mdcache_size" type="section"

gpdb-doc/dita/ref_guide/config_params/guc_config.ditamap

@@ -221,6 +221,7 @@
             <topicref href="guc-list.xml#optimizer_force_multistage_agg"/>
             <topicref href="guc-list.xml#optimizer_force_three_stage_scalar_dqa"/>
             <topicref href="guc-list.xml#optimizer_join_arity_for_associativity_commutativity"/>
+            <topicref href="guc-list.xml#optimizer_join_order"/>
             <topicref href="guc-list.xml#optimizer_join_order_threshold"/>
             <topicref href="guc-list.xml#optimizer_mdcache_size"/>
             <topicref href="guc-list.xml#optimizer_metadata_caching"/>