Add array_to_json and row_to_json functions.

Also move the escape_json function from explain.c to json.c where it
seems to belong.

Andrew Dunstan, Reviewd by Abhijit Menon-Sen.

Author: adunstan

doc/src/sgml/func.sgml

@@ -9617,6 +9617,65 @@ table2-mapping
   </sect2>
  </sect1>
 
+ <sect1 id="functions-json">
+  <title>JSON functions</title>
+
+  <indexterm zone="datatype-json">
+	<primary>JSON</primary>
+	<secondary>Functions and operators</secondary>
+  </indexterm>
+
+  <para>
+    This section descripbes the functions that are available for creating
+    JSON (see <xref linkend="datatype-json">) data.
+  </para>
+
+  <table id="functions-json-table">
+    <title>JSON Support Functions</title>
+    <tgroup cols="4">
+     <thead>
+      <row>
+       <entry>Function</entry>
+       <entry>Description</entry>
+       <entry>Example</entry>
+       <entry>Example Result</entry>
+      </row>
+     </thead>
+     <tbody>
+      <row>
+       <entry>
+         <indexterm>
+          <primary>array_to_json</primary>
+         </indexterm>
+         <literal>array_to_json(anyarray [, pretty_bool])</literal>
+       </entry>
+       <entry>
+         Returns the array as JSON. A Postgres multi-dimensional array 
+         becomes a JSON array of arrays. Line feeds will be added between 
+         dimension 1 elements if pretty_bool is true.
+       </entry>
+       <entry><literal>array_to_json('{{1,5},{99,100}}'::int[])</literal></entry>
+       <entry><literal>[[1,5],[99,100]]</literal></entry>
+      </row>
+      <row>
+       <entry>
+         <indexterm>
+          <primary>row_to_json</primary>
+         </indexterm>
+         <literal>row_to_json(record [, pretty_bool])</literal>
+       </entry>
+       <entry>
+         Returns the row as JSON. Line feeds will be added between level 
+         1 elements if pretty_bool is true.
+       </entry>
+       <entry><literal>row_to_json(row(1,'foo'))</literal></entry>
+       <entry><literal>{"f1":1,"f2":"foo"}</literal></entry>
+      </row>
+     </tbody>
+    </tgroup>
+   </table>
+
+ </sect1>
 
  <sect1 id="functions-sequence">
   <title>Sequence Manipulation Functions</title>

src/backend/commands/explain.c

@@ -24,6 +24,7 @@
 #include "rewrite/rewriteHandler.h"
 #include "tcop/tcopprot.h"
 #include "utils/builtins.h"
+#include "utils/json.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
 #include "utils/snapmgr.h"
@@ -99,7 +100,6 @@ static void ExplainDummyGroup(const char *objtype, const char *labelname,
 static void ExplainXMLTag(const char *tagname, int flags, ExplainState *es);
 static void ExplainJSONLineEnding(ExplainState *es);
 static void ExplainYAMLLineStarting(ExplainState *es);
-static void escape_json(StringInfo buf, const char *str);
 static void escape_yaml(StringInfo buf, const char *str);
 
 
@@ -2318,51 +2318,6 @@ ExplainYAMLLineStarting(ExplainState *es)
 	}
 }
 
-/*
- * Produce a JSON string literal, properly escaping characters in the text.
- */
-static void
-escape_json(StringInfo buf, const char *str)
-{
-	const char *p;
-
-	appendStringInfoCharMacro(buf, '\"');
-	for (p = str; *p; p++)
-	{
-		switch (*p)
-		{
-			case '\b':
-				appendStringInfoString(buf, "\\b");
-				break;
-			case '\f':
-				appendStringInfoString(buf, "\\f");
-				break;
-			case '\n':
-				appendStringInfoString(buf, "\\n");
-				break;
-			case '\r':
-				appendStringInfoString(buf, "\\r");
-				break;
-			case '\t':
-				appendStringInfoString(buf, "\\t");
-				break;
-			case '"':
-				appendStringInfoString(buf, "\\\"");
-				break;
-			case '\\':
-				appendStringInfoString(buf, "\\\\");
-				break;
-			default:
-				if ((unsigned char) *p < ' ')
-					appendStringInfo(buf, "\\u%04x", (int) *p);
-				else
-					appendStringInfoCharMacro(buf, *p);
-				break;
-		}
-	}
-	appendStringInfoCharMacro(buf, '\"');
-}
-
 /*
  * YAML is a superset of JSON; unfortuantely, the YAML quoting rules are
  * ridiculously complicated -- as documented in sections 5.3 and 7.3.3 of