Add documentation for JSON_TABLE PLAN DEFAULT clause

Author: Nikita Glukhov

doc/src/sgml/func.sgml

@@ -18595,6 +18595,10 @@ FROM
 JSON_TABLE (
   context_item, path_expression  PASSING { value AS varname } , ... 
   COLUMNS ( json_table_column , ... )
+  
+    PLAN DEFAULT ( { INNER | OUTER }  , { CROSS | UNION } 
+                 | { CROSS | UNION }  , { INNER | OUTER }  )
+  
 )
 
 where json_table_column is:
@@ -18656,7 +18660,8 @@ where json_table_column is:
       The rows produced by JSON_TABLE are laterally
       joined to the row that generated them, so you do not have to explicitly join
       the constructed view with the original table holding JSON
-      data.
+      data. Optionally, you can specify how to join the columns returned
+      by NESTED PATH using the PLAN DEFAULT clause.
      
 
      
@@ -18669,22 +18674,6 @@ where json_table_column is:
       the resulting rows are joined to the parent row.
      
 
-     
-      Columns with parent/child relationship are joined using
-      LEFT OUTER JOIN, so that the parent row
-      is always included into the output even if it does not have any child rows
-      after joining the data returned by NESTED PATH,
-      with NULL values inserted into the child columns if the corresponding
-      values are missing.
-     
-
-     
-      Sibling columns are joined using
-      FULL OUTER JOIN ON FALSE, so that both parent and child
-      rows are included into the output, with NULL values inserted
-      into both child and parrent columns for all missing values.
-     
-
     
     
      Parameters
@@ -18856,6 +18845,10 @@ where json_table_column is:
      JSON_TABLE expressions in an SQL statement.
     
 
+    
+     You can use the PLAN DEFAULT clause to define how
+     to join the columns returned by NESTED PATH clauses.
+    
     
    
 
@@ -18878,8 +18871,99 @@ where json_table_column is:
     
    
 
+   
+    
+     PLAN DEFAULT ( option [, ... ] )
+    
+    
+     
+      Defines how to join the data returned by NESTED PATH
+      clauses to the constructed view. The INNER and
+      OUTER options define the joining plan for parent/child
+      columns, while UNION and CROSS
+      affect the sibling columns. You can override the default plans for all
+      columns at once.
+     
+
+    
+     To join columns with parent/child relationship, you can use:
+    
+  
+   
+    
+     INNER
+    
+    
+
+    
+     Use INNER JOIN, so that the parent row
+     is omitted from the output if it does not have any child rows
+     after joining the data returned by NESTED PATH.
+    
+    
+   
+
+   
+    
+     OUTER
+    
+    
+
+    
+     Use LEFT OUTER JOIN, so that the parent row
+     is always included into the output even if it does not have any child rows
+     after joining the data returned by NESTED PATH, with NULL values
+     inserted into the child columns if the corresponding
+     values are missing.
+    
+    
+     This is the default option for joining columns with parent/child relationship.
+    
+    
+   
+  
+
+     
+     To join sibling columns, you can use:
+    
+
+  
+   
+    
+     UNION
+    
+    
+
+    
+     Use FULL OUTER JOIN ON FALSE, so that both parent and child
+     rows are included into the output, with NULL values inserted
+     into both child and parrent columns for all missing values.
+    
+    
+     This is the default option for joining sibling columns.
+    
+    
+   
+
+   
+    
+     CROSS
+    
+    
+
+    
+     Use CROSS JOIN, so that the output includes 
+     a row for every possible combination of rows from the left-hand
+     and the right-hand columns.
+    
+    
+   
+
   
 
+    
+   
+