SQL JSON functions

This Patch introduces three SQL standard JSON functions:

JSON() (incorrectly mentioned in my commit message for f4fb45d)
JSON_SCALAR()
JSON_SERIALIZE()

JSON() produces json values from text, bytea, json or jsonb values, and
has facilitites for handling duplicate keys.
JSON_SCALAR() produces a json value from any scalar sql value, including
json and jsonb.
JSON_SERIALIZE() produces text or bytea from input which containis or
represents json or jsonb;

For the most part these functions don't add any significant new
capabilities, but they will be of use to users wanting standard
compliant JSON handling.

Nikita Glukhov

Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.

Discussion: https://postgr.es/m/[email protected]

Author: adunstan

doc/src/sgml/keywords/sql2016-02-reserved.txt

@@ -156,12 +156,15 @@ INTERVAL
 INTO
 IS
 JOIN
+JSON
 JSON_ARRAY
 JSON_ARRAYAGG
 JSON_EXISTS
 JSON_OBJECT
 JSON_OBJECTAGG
 JSON_QUERY
+JSON_SCALAR
+JSON_SERIALIZE
 JSON_TABLE
 JSON_TABLE_PRIMITIVE
 JSON_VALUE

src/backend/executor/execExpr.c

@@ -47,6 +47,8 @@
 #include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/datum.h"
+#include "utils/json.h"
+#include "utils/jsonb.h"
 #include "utils/jsonpath.h"
 #include "utils/lsyscache.h"
 #include "utils/typcache.h"
@@ -2460,6 +2462,12 @@ ExecInitExprRec(Expr *node, ExprState *state,
 				{
 					ExecInitExprRec(ctor->func, state, resv, resnull);
 				}
+				else if ((ctor->type == JSCTOR_JSON_PARSE && !ctor->unique) ||
+						 ctor->type == JSCTOR_JSON_SERIALIZE)
+				{
+					/* Use the value of the first argument as a result */
+					ExecInitExprRec(linitial(args), state, resv, resnull);
+				}
 				else
 				{
 					scratch.opcode = EEOP_JSON_CONSTRUCTOR;
@@ -2492,6 +2500,43 @@ ExecInitExprRec(Expr *node, ExprState *state,
 						argno++;
 					}
 
+					/* prepare type cache for datum_to_json[b]() */
+					if (ctor->type == JSCTOR_JSON_SCALAR)
+					{
+						bool		is_jsonb =
+							ctor->returning->format->format_type == JS_FORMAT_JSONB;
+
+						scratch.d.json_constructor.arg_type_cache =
+							palloc(sizeof(*scratch.d.json_constructor.arg_type_cache) * nargs);
+
+						for (int i = 0; i < nargs; i++)
+						{
+							int			category;
+							Oid			outfuncid;
+							Oid			typid = scratch.d.json_constructor.arg_types[i];
+
+							if (is_jsonb)
+							{
+								JsonbTypeCategory jbcat;
+
+								jsonb_categorize_type(typid, &jbcat, &outfuncid);
+
+								category = (int) jbcat;
+							}
+							else
+							{
+								JsonTypeCategory jscat;
+
+								json_categorize_type(typid, &jscat, &outfuncid);
+
+								category = (int) jscat;
+							}
+
+							scratch.d.json_constructor.arg_type_cache[i].outfuncid = outfuncid;
+							scratch.d.json_constructor.arg_type_cache[i].category = category;
+						}
+					}
+
 					ExprEvalPushStep(state, &scratch);
 				}
 

src/backend/executor/execExprInterp.c

@@ -3982,7 +3982,7 @@ ExecEvalJsonIsPredicate(ExprState *state, ExprEvalStep *op)
 		 * JSON text validation.
 		 */
 		if (res && (pred->unique_keys || exprtype == TEXTOID))
-			res = json_validate(json, pred->unique_keys);
+			res = json_validate(json, pred->unique_keys, false);
 	}
 	else if (exprtype == JSONBOID)
 	{
@@ -4527,6 +4527,46 @@ ExecEvalJsonConstructor(ExprState *state, ExprEvalStep *op,
 										 op->d.json_constructor.arg_types,
 										 op->d.json_constructor.constructor->absent_on_null,
 										 op->d.json_constructor.constructor->unique);
+	else if (ctor->type == JSCTOR_JSON_SCALAR)
+	{
+		if (op->d.json_constructor.arg_nulls[0])
+		{
+			res = (Datum) 0;
+			isnull = true;
+		}
+		else
+		{
+			Datum		value = op->d.json_constructor.arg_values[0];
+			int			category = op->d.json_constructor.arg_type_cache[0].category;
+			Oid			outfuncid = op->d.json_constructor.arg_type_cache[0].outfuncid;
+
+			if (is_jsonb)
+				res = to_jsonb_worker(value, category, outfuncid);
+			else
+				res = to_json_worker(value, category, outfuncid);
+		}
+	}
+	else if (ctor->type == JSCTOR_JSON_PARSE)
+	{
+		if (op->d.json_constructor.arg_nulls[0])
+		{
+			res = (Datum) 0;
+			isnull = true;
+		}
+		else
+		{
+			Datum		value = op->d.json_constructor.arg_values[0];
+			text	   *js = DatumGetTextP(value);
+
+			if (is_jsonb)
+				res = jsonb_from_text(js, true);
+			else
+			{
+				(void) json_validate(js, true, true);
+				res = value;
+			}
+		}
+	}
 	else
 	{
 		res = (Datum) 0;

src/backend/nodes/copyfuncs.c

@@ -2345,6 +2345,50 @@ _copyJsonValueExpr(const JsonValueExpr *from)
 	return newnode;
 }
 
+/*
+ * _copyJsonParseExpr
+ */
+static JsonParseExpr *
+_copyJsonParseExpr(const JsonParseExpr *from)
+{
+	JsonParseExpr  *newnode = makeNode(JsonParseExpr);
+
+	COPY_NODE_FIELD(expr);
+	COPY_SCALAR_FIELD(unique_keys);
+	COPY_LOCATION_FIELD(location);
+
+	return newnode;
+}
+
+/*
+ * _copyJsonScalarExpr
+ */
+static JsonScalarExpr *
+_copyJsonScalarExpr(const JsonScalarExpr *from)
+{
+	JsonScalarExpr *newnode = makeNode(JsonScalarExpr);
+
+	COPY_NODE_FIELD(expr);
+	COPY_LOCATION_FIELD(location);
+
+	return newnode;
+}
+
+/*
+ * _copyJsonSerializeExpr
+ */
+static JsonSerializeExpr *
+_copyJsonSerializeExpr(const JsonSerializeExpr *from)
+{
+	JsonSerializeExpr *newnode = makeNode(JsonSerializeExpr);
+
+	COPY_NODE_FIELD(expr);
+	COPY_NODE_FIELD(output);
+	COPY_LOCATION_FIELD(location);
+
+	return newnode;
+}
+
 /*
  * _copyJsonConstructorExpr
  */
@@ -5744,6 +5788,15 @@ copyObjectImpl(const void *from)
 		case T_JsonValueExpr:
 			retval = _copyJsonValueExpr(from);
 			break;
+		case T_JsonParseExpr:
+			retval = _copyJsonParseExpr(from);
+			break;
+		case T_JsonScalarExpr:
+			retval = _copyJsonScalarExpr(from);
+			break;
+		case T_JsonSerializeExpr:
+			retval = _copyJsonSerializeExpr(from);
+			break;
 		case T_JsonKeyValue:
 			retval = _copyJsonKeyValue(from);
 			break;

src/backend/nodes/equalfuncs.c

@@ -871,6 +871,35 @@ _equalJsonValueExpr(const JsonValueExpr *a, const JsonValueExpr *b)
 	return true;
 }
 
+static bool
+_equalJsonParseExpr(const JsonParseExpr *a, const JsonParseExpr *b)
+{
+	COMPARE_NODE_FIELD(expr);
+	COMPARE_SCALAR_FIELD(unique_keys);
+	COMPARE_LOCATION_FIELD(location);
+
+	return true;
+}
+
+static bool
+_equalJsonScalarExpr(const JsonScalarExpr *a, const JsonScalarExpr *b)
+{
+	COMPARE_NODE_FIELD(expr);
+	COMPARE_LOCATION_FIELD(location);
+
+	return true;
+}
+
+static bool
+_equalJsonSerializeExpr(const JsonSerializeExpr *a, const JsonSerializeExpr *b)
+{
+	COMPARE_NODE_FIELD(expr);
+	COMPARE_NODE_FIELD(output);
+	COMPARE_LOCATION_FIELD(location);
+
+	return true;
+}
+
 static bool
 _equalJsonConstructorExpr(const JsonConstructorExpr *a, const JsonConstructorExpr *b)
 {
@@ -3661,6 +3690,15 @@ equal(const void *a, const void *b)
 		case T_JsonValueExpr:
 			retval = _equalJsonValueExpr(a, b);
 			break;
+		case T_JsonParseExpr:
+			retval = _equalJsonParseExpr(a, b);
+			break;
+		case T_JsonScalarExpr:
+			retval = _equalJsonScalarExpr(a, b);
+			break;
+		case T_JsonSerializeExpr:
+			retval = _equalJsonSerializeExpr(a, b);
+			break;
 		case T_JsonConstructorExpr:
 			retval = _equalJsonConstructorExpr(a, b);
 			break;

src/backend/nodes/nodeFuncs.c

@@ -4363,6 +4363,20 @@ raw_expression_tree_walker(Node *node,
 					return true;
 			}
 			break;
+		case T_JsonParseExpr:
+			return walker(((JsonParseExpr *) node)->expr, context);
+		case T_JsonScalarExpr:
+			return walker(((JsonScalarExpr *) node)->expr, context);
+		case T_JsonSerializeExpr:
+			{
+				JsonSerializeExpr *jse = (JsonSerializeExpr *) node;
+
+				if (walker(jse->expr, context))
+					return true;
+				if (walker(jse->output, context))
+					return true;
+			}
+			break;
 		case T_JsonConstructorExpr:
 			{
 				JsonConstructorExpr *ctor = (JsonConstructorExpr *) node;