Add several generator functions for jsonb that exist for json.

The functions are:
    to_jsonb()
    jsonb_object()
    jsonb_build_object()
    jsonb_build_array()
    jsonb_agg()
    jsonb_object_agg()

Also along the way some better logic is implemented in
json_categorize_type() to match that in the newly implemented
jsonb_categorize_type().

Andrew Dunstan, reviewed by Pavel Stehule and Alvaro Herrera.

Author: adunstan

doc/src/sgml/func.sgml

@@ -10245,9 +10245,10 @@ table2-mapping
 
   <para>
    <xref linkend="functions-json-creation-table"> shows the functions that are
-   available for creating <type>json</type> values.
-   (Currently, there are no equivalent functions for <type>jsonb</>, but you
-   can cast the result of one of these functions to <type>jsonb</>.)
+   available for creating <type>json</type> and <type>jsonb</type> values.
+   (There are no equivalent functions for <type>jsonb</>, of the <literal>row_to_json</>
+   and <literal>array_to_json</> functions. However, the <literal>to_jsonb</>
+   function supplies much the same functionality as these functions would.)
   </para>
 
   <indexterm>
@@ -10268,6 +10269,18 @@ table2-mapping
   <indexterm>
    <primary>json_object</primary>
   </indexterm>
+  <indexterm>
+   <primary>to_jsonb</primary>
+  </indexterm>
+  <indexterm>
+   <primary>jsonb_build_array</primary>
+  </indexterm>
+  <indexterm>
+   <primary>jsonb_build_object</primary>
+  </indexterm>
+  <indexterm>
+   <primary>jsonb_object</primary>
+  </indexterm>
 
   <table id="functions-json-creation-table">
     <title>JSON Creation Functions</title>
@@ -10282,17 +10295,18 @@ table2-mapping
      </thead>
      <tbody>
       <row>
+       <entry><para><literal>to_json(anyelement)</literal>
+          </para><para><literal>to_jsonb(anyelement)</literal>
+       </para></entry>
        <entry>
-         <literal>to_json(anyelement)</literal>
-       </entry>
-       <entry>
-         Returns the value as JSON.  Arrays and composites are converted
+         Returns the value as <type>json</> or <type>jsonb</>.
+         Arrays and composites are converted
          (recursively) to arrays and objects; otherwise, if there is a cast
          from the type to <type>json</type>, the cast function will be used to
-         perform the conversion; otherwise, a JSON scalar value is produced.
+         perform the conversion; otherwise, a scalar value is produced.
          For any scalar type other than a number, a Boolean, or a null value,
-         the text representation will be used, properly quoted and escaped
-         so that it is a valid JSON string.
+         the text representation will be used, in such a fashion that it is a 
+         valid <type>json</> or <type>jsonb</> value.
        </entry>
        <entry><literal>to_json('Fred said "Hi."'::text)</literal></entry>
        <entry><literal>"Fred said \"Hi.\""</literal></entry>
@@ -10321,9 +10335,9 @@ table2-mapping
        <entry><literal>{"f1":1,"f2":"foo"}</literal></entry>
       </row>
       <row>
-       <entry>
-         <literal>json_build_array(VARIADIC "any")</literal>
-       </entry>
+       <entry><para><literal>json_build_array(VARIADIC "any")</literal>
+          </para><para><literal>jsonb_build_array(VARIADIC "any")</literal>
+       </para></entry>
        <entry>
          Builds a possibly-heterogeneously-typed JSON array out of a variadic
          argument list.
@@ -10332,9 +10346,9 @@ table2-mapping
        <entry><literal>[1, 2, "3", 4, 5]</literal></entry>
       </row>
       <row>
-       <entry>
-         <literal>json_build_object(VARIADIC "any")</literal>
-       </entry>
+       <entry><para><literal>json_build_object(VARIADIC "any")</literal>
+          </para><para><literal>jsonb_build_object(VARIADIC "any")</literal>
+       </para></entry>
        <entry>
          Builds a JSON object out of a variadic argument list.  By
          convention, the argument list consists of alternating
@@ -10344,9 +10358,9 @@ table2-mapping
        <entry><literal>{"foo": 1, "bar": 2}</literal></entry>
       </row>
       <row>
-       <entry>
-         <literal>json_object(text[])</literal>
-       </entry>
+       <entry><para><literal>json_object(text[])</literal>
+          </para><para><literal>jsonb_object(text[])</literal>
+       </para></entry>
        <entry>
          Builds a JSON object out of a text array.  The array must have either
          exactly one dimension with an even number of members, in which case
@@ -10359,9 +10373,9 @@ table2-mapping
        <entry><literal>{"a": "1", "b": "def", "c": "3.5"}</literal></entry>
       </row>
       <row>
-       <entry>
-         <literal>json_object(keys text[], values text[])</literal>
-       </entry>
+       <entry><para><literal>json_object(keys text[], values text[])</literal>
+          </para><para><literal>json_object(keys text[], values text[])</literal>
+       </para></entry>
        <entry>
          This form of <function>json_object</> takes keys and values pairwise from two separate
          arrays. In all other respects it is identical to the one-argument form.
@@ -10780,7 +10794,8 @@ table2-mapping
     function <function>json_agg</function> which aggregates record
     values as JSON, and the aggregate function
     <function>json_object_agg</function> which aggregates pairs of values
-    into a JSON object.
+    into a JSON object, and their <type>jsonb</type> equivalents,
+    <function>jsonb_agg</> and <function>jsonb_object_agg</>.
   </para>
 
  </sect1>
@@ -12224,6 +12239,22 @@ NULL baz</literallayout>(3 rows)</entry>
       <entry>aggregates records as a JSON array of objects</entry>
      </row>
 
+     <row>
+      <entry>
+       <indexterm>
+        <primary>jsonb_agg</primary>
+       </indexterm>
+       <function>jsonb_agg(<replaceable class="parameter">record</replaceable>)</function>
+      </entry>
+      <entry>
+       <type>record</type>
+      </entry>
+      <entry>
+       <type>jsonb</type>
+      </entry>
+      <entry>aggregates records as a JSON array of objects</entry>
+     </row>
+
      <row>
       <entry>
        <indexterm>
@@ -12240,6 +12271,22 @@ NULL baz</literallayout>(3 rows)</entry>
       <entry>aggregates name/value pairs as a JSON object</entry>
      </row>
 
+     <row>
+      <entry>
+       <indexterm>
+        <primary>jsonb_object_agg</primary>
+       </indexterm>
+       <function>jsonb_object_agg(<replaceable class="parameter">name</replaceable>, <replaceable class="parameter">value</replaceable>)</function>
+      </entry>
+      <entry>
+       <type>("any", "any")</type>
+      </entry>
+      <entry>
+       <type>jsonb</type>
+      </entry>
+      <entry>aggregates name/value pairs as a JSON object</entry>
+     </row>
+
      <row>
       <entry>
        <indexterm>
@@ -12386,8 +12433,8 @@ SELECT count(*) FROM sometable;
 
   <para>
    The aggregate functions <function>array_agg</function>,
-   <function>json_agg</function>,
-   <function>json_object_agg</function>,
+   <function>json_agg</function>, <function>jsonb_agg</function>,
+   <function>json_object_agg</function>, <function>jsonb_object_agg</function>,
    <function>string_agg</function>,
    and <function>xmlagg</function>, as well as similar user-defined
    aggregate functions, produce meaningfully different result values

src/backend/utils/adt/json.c

@@ -15,7 +15,6 @@
 
 #include "access/htup_details.h"
 #include "access/transam.h"
-#include "catalog/pg_cast.h"
 #include "catalog/pg_type.h"
 #include "executor/spi.h"
 #include "lib/stringinfo.h"
@@ -1281,10 +1280,14 @@ json_categorize_type(Oid typoid,
 	/* Look through any domain */
 	typoid = getBaseType(typoid);
 
-	/* We'll usually need to return the type output function */
-	getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
+	*outfuncoid = InvalidOid;
+
+	/*
+	 * We need to get the output function for everything except date and
+	 * timestamp types, array and composite types, booleans,
+	 * and non-builtin types  where there's a cast to json.
+	 */
 
-	/* Check for known types */
 	switch (typoid)
 	{
 		case BOOLOID:
@@ -1297,6 +1300,7 @@ json_categorize_type(Oid typoid,
 		case FLOAT4OID:
 		case FLOAT8OID:
 		case NUMERICOID:
+			getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
 			*tcategory = JSONTYPE_NUMERIC;
 			break;
 
@@ -1314,6 +1318,7 @@ json_categorize_type(Oid typoid,
 
 		case JSONOID:
 		case JSONBOID:
+			getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
 			*tcategory = JSONTYPE_JSON;
 			break;
 
@@ -1330,23 +1335,26 @@ json_categorize_type(Oid typoid,
 				/* but let's look for a cast to json, if it's not built-in */
 				if (typoid >= FirstNormalObjectId)
 				{
-					HeapTuple	tuple;
+					Oid castfunc;
+					CoercionPathType ctype;
 
-					tuple = SearchSysCache2(CASTSOURCETARGET,
-											ObjectIdGetDatum(typoid),
-											ObjectIdGetDatum(JSONOID));
-					if (HeapTupleIsValid(tuple))
+					ctype = find_coercion_pathway(JSONOID, typoid,
+												  COERCION_EXPLICIT, &castfunc);
+					if (ctype == COERCION_PATH_FUNC && OidIsValid(castfunc))
 					{
-						Form_pg_cast castForm = (Form_pg_cast) GETSTRUCT(tuple);
-
-						if (castForm->castmethod == COERCION_METHOD_FUNCTION)
-						{
-							*tcategory = JSONTYPE_CAST;
-							*outfuncoid = castForm->castfunc;
-						}
-
-						ReleaseSysCache(tuple);
+						*tcategory = JSONTYPE_CAST;
+						*outfuncoid = castfunc;
 					}
+					else
+					{
+						/* non builtin type with no cast */
+						getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
+					}
+				}
+				else
+				{
+					/* any other builtin type */
+					getTypeOutputInfo(typoid, outfuncoid, &typisvarlena);
 				}
 			}
 			break;