Add implicit FORMAT JSON for composite JSON_TABLE columns

Author: Nikita Glukhov

doc/src/sgml/func.sgml

@@ -18604,15 +18604,16 @@ JSON_TABLE (
 where <replaceable class="parameter">json_table_column</replaceable> is:
 </phrase>
     <replaceable>name</replaceable> <replaceable>type</replaceable> [ PATH <replaceable>json_path_specification</replaceable> ]
+        [ { WITHOUT | WITH { CONDITIONAL | [UNCONDITIONAL] } } [ ARRAY ] WRAPPER ]
+        [ { KEEP | OMIT } QUOTES [ ON SCALAR STRING ] ]
         [ { ERROR | NULL | DEFAULT <replaceable>expression</replaceable> } ON EMPTY ]
         [ { ERROR | NULL | DEFAULT <replaceable>expression</replaceable> } ON ERROR ]
   | <replaceable>name</replaceable> <replaceable>type</replaceable> FORMAT <replaceable>json_representation</replaceable>
         [ PATH <replaceable>json_path_specification</replaceable> ]
-        [ { WITHOUT | WITH { CONDITIONAL | [UNCONDITIONAL] } }
-          [ ARRAY ] WRAPPER ]
+        [ { WITHOUT | WITH { CONDITIONAL | [UNCONDITIONAL] } } [ ARRAY ] WRAPPER ]
         [ { KEEP | OMIT } QUOTES [ ON SCALAR STRING ] ]
-        [ { ERROR | NULL | EMPTY { ARRAY | OBJECT } } ON EMPTY ]
-        [ { ERROR | NULL | EMPTY { ARRAY | OBJECT } } ON ERROR ]
+        [ { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON EMPTY ]
+        [ { ERROR | NULL | EMPTY { ARRAY | OBJECT } | DEFAULT expression } ON ERROR ]
   | <replaceable>name</replaceable> <replaceable>type</replaceable> EXISTS [ PATH <replaceable>json_path_specification</replaceable> ]
         [ { ERROR | TRUE | FALSE | UNKNOWN } ON ERROR ]
   | NESTED PATH <replaceable>json_path_specification</replaceable> [ AS <replaceable>path_name</replaceable> ]
@@ -18718,7 +18719,7 @@ where <replaceable class="parameter">json_table_column</replaceable> is:
     <para>
      The <literal>COLUMNS</literal> clause defining the schema of the
      constructed view. In this clause, you must specify all the columns
-     to be filled with SQL/JSON items. Only scalar column types are supported.
+     to be filled with SQL/JSON items.
      The <replaceable class="parameter">json_table_column</replaceable>
      expression has the following syntax variants:
     </para>
@@ -18746,11 +18747,22 @@ where <replaceable class="parameter">json_table_column</replaceable> is:
      In this case, the column name must correspond to one of the
      keys within the SQL/JSON item produced by the row pattern.
     </para>
+    <para>
+      Internally, <xref linkend="functions-jsonvalue"/> and
+      <xref linkend="functions-jsonquery"/> are used to produce resulting values.
+      <xref linkend="functions-jsonquery"/> is used for JSON, array, and
+      composite column types, <xref linkend="functions-jsonvalue"/> is used for
+      other types.
+    </para>
     <para>
      Optionally, you can add <literal>ON EMPTY</literal> and
-     <literal>ON ERROR</literal> clauses to define how to handle
-     missing values or structural errors. These clauses have the same syntax
-     and semantics as in <xref linkend="functions-jsonvalue"/>.
+     <literal>ON ERROR</literal> clauses to define how to handle missing values
+     or structural errors.
+     <literal>WRAPPER</literal> and <literal>QUOTES</literal> clauses can only
+     be used with JSON, array, and composite types.
+     These clauses have the same syntax and semantics as in
+     <xref linkend="functions-jsonvalue"/> and
+     <xref linkend="functions-jsonquery"/>.
     </para>
     </listitem>
    </varlistentry>
@@ -18777,6 +18789,10 @@ where <replaceable class="parameter">json_table_column</replaceable> is:
      In this case, the column name must correspond to one of the
      keys within the SQL/JSON item produced by the row pattern.
     </para>
+    <para>
+      Internally, <xref linkend="functions-jsonquery"/> is used to produce
+      resulting values.
+    </para>
     <para>
      Optionally, you can add <literal>WRAPPER</literal>, <literal>QUOTES</literal>,
      <literal>ON EMPTY</literal> and <literal>ON ERROR</literal> clauses

src/backend/parser/gram.y

@@ -15175,18 +15175,20 @@ json_table_ordinality_column_definition:
 json_table_regular_column_definition:
 			ColId Typename
 			json_table_column_path_specification_clause_opt
+			json_wrapper_clause_opt
+			json_quotes_clause_opt
 			json_value_on_behavior_clause_opt
 				{
 					JsonTableColumn *n = makeNode(JsonTableColumn);
 					n->coltype = JTC_REGULAR;
 					n->name = $1;
 					n->typeName = $2;
 					n->format = makeJsonFormat(JS_FORMAT_DEFAULT, JS_ENC_DEFAULT, -1);
-					n->wrapper = JSW_NONE;
-					n->omit_quotes = false;
+					n->wrapper = $4; /* JSW_NONE */
+					n->omit_quotes = $5; /* false */
 					n->pathspec = $3;
-					n->on_empty = $4.on_empty;
-					n->on_error = $4.on_error;
+					n->on_empty = $6.on_empty;
+					n->on_error = $6.on_error;
 					n->location = @1;
 					$$ = (Node *) n;
 				}

src/backend/parser/parse_jsontable.c

@@ -26,6 +26,7 @@
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
+#include "parser/parse_type.h"
 #include "utils/builtins.h"
 #include "utils/json.h"
 #include "utils/lsyscache.h"
@@ -212,6 +213,28 @@ transformJsonTableChildColumns(JsonTableContext *cxt, List *columns)
 	return res;
 }
 
+/* Check whether type is json/jsonb, array, or record. */
+static bool
+typeIsComposite(Oid typid)
+{
+	if (typid == JSONOID ||
+		typid == JSONBOID ||
+		typid == RECORDOID ||
+		type_is_array(typid))
+		return true;
+
+	switch (get_typtype(typid))
+	{
+		case TYPTYPE_COMPOSITE:
+			return true;
+
+		case TYPTYPE_DOMAIN:
+			return typeIsComposite(getBaseType(typid));
+	}
+
+	return false;
+}
+
 /* Append transformed non-nested JSON_TABLE columns to the TableFunc node */
 static void
 appendJsonTableColumns(JsonTableContext *cxt, List *columns)
@@ -261,6 +284,26 @@ appendJsonTableColumns(JsonTableContext *cxt, List *columns)
 				break;
 
 			case JTC_REGULAR:
+				typenameTypeIdAndMod(pstate, rawc->typeName, &typid, &typmod);
+
+				/*
+				 * Use implicit FORMAT JSON for composite types (arrays and
+				 * records)
+				 */
+				if (typeIsComposite(typid))
+					rawc->coltype = JTC_FORMATTED;
+				else if (rawc->wrapper != JSW_NONE)
+					ereport(ERROR,
+							(errcode(ERRCODE_SYNTAX_ERROR),
+							 errmsg("cannot use WITH WRAPPER clause with scalar columns"),
+							 parser_errposition(pstate, rawc->location)));
+				else if (rawc->omit_quotes)
+					ereport(ERROR,
+							(errcode(ERRCODE_SYNTAX_ERROR),
+							 errmsg("cannot use OMIT QUOTES clause with scalar columns"),
+							 parser_errposition(pstate, rawc->location)));
+
+				/* FALLTHROUGH */
 			case JTC_EXISTS:
 			case JTC_FORMATTED:
 				{

src/backend/utils/adt/ruleutils.c

@@ -10503,9 +10503,18 @@ get_json_table_columns(TableFunc *tf, JsonTableParentNode *node,
 		else
 		{
 			if (colexpr->op == IS_JSON_QUERY)
-				appendStringInfoString(buf,
-									   colexpr->format->format == JS_FORMAT_JSONB ?
-									   " FORMAT JSONB" : " FORMAT JSON");
+			{
+				char		typcategory;
+				bool		typispreferred;
+
+				get_type_category_preferred(typid, &typcategory, &typispreferred);
+
+				if (typcategory == TYPCATEGORY_STRING)
+					appendStringInfoString(buf,
+										   colexpr->format->format == JS_FORMAT_JSONB ?
+										   " FORMAT JSONB" : " FORMAT JSON");
+			}
+
 			default_behavior = JSON_BEHAVIOR_NULL;
 		}