Allow variable jsonpath specifications

Author: Nikita Glukhov

contrib/pg_stat_statements/pg_stat_statements.c

@@ -2847,7 +2847,7 @@ JumbleExpr(pgssJumbleState *jstate, Node *node)
 
 				APP_JUMB(jexpr->op);
 				JumbleExpr(jstate, jexpr->raw_expr);
-				JumbleExpr(jstate, (Node *) jexpr->path_spec);
+				JumbleExpr(jstate, jexpr->path_spec);
 				JumbleExpr(jstate, (Node *) jexpr->passing.values);
 				JumbleExpr(jstate, jexpr->on_empty.default_expr);
 				JumbleExpr(jstate, jexpr->on_error.default_expr);

src/backend/executor/execExpr.c

@@ -2135,6 +2135,13 @@ ExecInitExprRec(Expr *node, ExprState *state,
 								&scratch.d.jsonexpr.raw_expr->value,
 								&scratch.d.jsonexpr.raw_expr->isnull);
 
+				scratch.d.jsonexpr.pathspec =
+					palloc(sizeof(*scratch.d.jsonexpr.pathspec));
+
+				ExecInitExprRec((Expr *) jexpr->path_spec, state,
+								&scratch.d.jsonexpr.pathspec->value,
+								&scratch.d.jsonexpr.pathspec->isnull);
+
 				scratch.d.jsonexpr.formatted_expr =
 						ExecInitExpr((Expr *) jexpr->formatted_expr,
 									 state->parent);

src/backend/executor/execExprInterp.c

@@ -4464,7 +4464,7 @@ ExecEvalJson(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
 	*op->resnull = true;		/* until we get a result */
 	*op->resvalue = (Datum) 0;
 
-	if (op->d.jsonexpr.raw_expr->isnull)
+	if (op->d.jsonexpr.raw_expr->isnull || op->d.jsonexpr.pathspec->isnull)
 	{
 		/* execute domain checks for NULLs */
 		(void) ExecEvalJsonExprCoercion(op, econtext, res, op->resnull);
@@ -4476,8 +4476,7 @@ ExecEvalJson(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
 	}
 
 	item = op->d.jsonexpr.raw_expr->value;
-
-	path = DatumGetJsonPathP(jexpr->path_spec->constvalue);
+	path = DatumGetJsonPathP(op->d.jsonexpr.pathspec->value);
 
 	/* reset JSON path variable contexts */
 	foreach(lc, op->d.jsonexpr.args)

src/backend/nodes/copyfuncs.c

@@ -2483,7 +2483,7 @@ _copyJsonCommon(const JsonCommon *from)
 	JsonCommon	   *newnode = makeNode(JsonCommon);
 
 	COPY_NODE_FIELD(expr);
-	COPY_STRING_FIELD(pathspec);
+	COPY_NODE_FIELD(pathspec);
 	COPY_STRING_FIELD(pathname);
 	COPY_NODE_FIELD(passing);
 	COPY_LOCATION_FIELD(location);

src/backend/nodes/nodeFuncs.c

@@ -3192,6 +3192,7 @@ expression_tree_mutator(Node *node,
 				JsonExpr    *newnode;
 
 				FLATCOPY(newnode, jexpr, JsonExpr);
+				MUTATE(newnode->raw_expr, jexpr->path_spec, Node *);
 				MUTATE(newnode->raw_expr, jexpr->raw_expr, Node *);
 				MUTATE(newnode->formatted_expr, jexpr->formatted_expr, Node *);
 				MUTATE(newnode->result_coercion, jexpr->result_coercion, JsonCoercion *);
@@ -3963,6 +3964,8 @@ raw_expression_tree_walker(Node *node,
 
 				if (walker(jc->expr, context))
 					return true;
+				if (walker(jc->pathspec, context))
+					return true;
 				if (walker(jc->passing, context))
 					return true;
 			}

src/backend/parser/gram.y

@@ -612,6 +612,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 					json_aggregate_func
 					json_object_aggregate_constructor
 					json_array_aggregate_constructor
+					json_path_specification
 
 %type <list>		json_arguments
 					json_passing_clause_opt
@@ -621,8 +622,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 %type <typnam>		json_returning_clause_opt
 
-%type <str>			json_path_specification
-					json_table_path_name
+%type <str>			json_table_path_name
 					json_as_path_name_clause_opt
 
 %type <ival>		json_encoding
@@ -827,6 +827,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  */
 %nonassoc	UNBOUNDED		/* ideally should have same precedence as IDENT */
 %nonassoc	ERROR_P EMPTY_P DEFAULT ABSENT /* JSON error/empty behavior */
+%nonassoc	FALSE_P KEEP OMIT PASSING TRUE_P UNKNOWN
 %nonassoc	IDENT GENERATED NULL_P PARTITION RANGE ROWS GROUPS PRECEDING FOLLOWING CUBE ROLLUP
 %left		Op OPERATOR		/* multi-character ops and user-defined operators */
 %left		'+' '-'
@@ -14804,7 +14805,7 @@ json_context_item:
 		;
 
 json_path_specification:
-			Sconst									{ $$ = $1; }
+			a_expr									{ $$ = $1; }
 		;
 
 json_as_path_name_clause_opt:

src/backend/parser/parse_expr.c

@@ -4414,7 +4414,7 @@ static JsonExpr *
 transformJsonExprCommon(ParseState *pstate, JsonFuncExpr *func)
 {
 	JsonExpr   *jsexpr = makeNode(JsonExpr);
-	Datum		jsonpath;
+	Node	   *pathspec;
 	JsonFormatType format;
 
 	if (func->common->pathname)
@@ -4445,12 +4445,19 @@ transformJsonExprCommon(ParseState *pstate, JsonFuncExpr *func)
 
 	jsexpr->format = func->common->expr->format;
 
-	/* parse JSON path string */
-	jsonpath = DirectFunctionCall1(jsonpath_in,
-									CStringGetDatum(func->common->pathspec));
+	pathspec = transformExprRecurse(pstate, func->common->pathspec);
 
-	jsexpr->path_spec = makeConst(JSONPATHOID, -1, InvalidOid, -1,
-								  jsonpath, false, false);
+	jsexpr->path_spec =
+		coerce_to_target_type(pstate, pathspec, exprType(pathspec),
+							  JSONPATHOID, -1,
+							  COERCION_EXPLICIT, COERCE_IMPLICIT_CAST,
+							  exprLocation(pathspec));
+	if (!jsexpr->path_spec)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATATYPE_MISMATCH),
+				 errmsg("JSON path expression must be type %s, not type %s",
+						"jsonpath", format_type_be(exprType(pathspec))),
+				 parser_errposition(pstate, exprLocation(pathspec))));
 
 	/* transform and coerce to json[b] passing arguments */
 	transformJsonPassingArgs(pstate, format, func->common->passing,

src/backend/utils/adt/ruleutils.c

@@ -467,6 +467,8 @@ static void add_cast_to(StringInfo buf, Oid typid);
 static char *generate_qualified_type_name(Oid typid);
 static text *string_to_text(char *str);
 static char *flatten_reloptions(Oid relid);
+static void get_json_path_spec(Node *path_spec, deparse_context *context,
+				   bool showimplicit);
 
 #define only_marker(rte)  ((rte)->inh ? "" : "ONLY ")
 
@@ -7676,6 +7678,19 @@ get_rule_expr_paren(Node *node, deparse_context *context,
 		appendStringInfoChar(context->buf, ')');
 }
 
+
+/*
+ * get_json_path_spec		- Parse back a JSON path specification
+ */
+static void
+get_json_path_spec(Node *path_spec, deparse_context *context, bool showimplicit)
+{
+	if (IsA(path_spec, Const))
+		get_const_expr((Const *) path_spec, context, -1);
+	else
+		get_rule_expr(path_spec, context, showimplicit);
+}
+
 /*
  * get_json_format			- Parse back a JsonFormat structure
  */
@@ -8933,7 +8948,7 @@ get_rule_expr(Node *node, deparse_context *context,
 
 				appendStringInfoString(buf, ", ");
 
-				get_const_expr(jexpr->path_spec, context, -1);
+				get_json_path_spec(jexpr->path_spec, context, showimplicit);
 
 				if (jexpr->passing.values)
 				{

src/include/executor/execExpr.h

@@ -654,7 +654,8 @@ typedef struct ExprEvalStep
 			{
 				Datum		value;
 				bool		isnull;
-			}		   *raw_expr;			/* raw context item value */
+			}		   *raw_expr,			/* raw context item value */
+					   *pathspec;			/* path specification value */
 
 			ExprState  *formatted_expr;		/* formatted context item */
 			ExprState  *result_expr;		/* coerced to output type */

src/include/nodes/parsenodes.h

@@ -1488,7 +1488,7 @@ typedef struct JsonCommon
 {
 	NodeTag		type;
 	JsonValueExpr *expr;		/* context item expression */
-	JsonPathSpec pathspec;		/* JSON path specification */
+	Node	   *pathspec;		/* JSON path specification expression */
 	char	   *pathname;		/* path name, if any */
 	List	   *passing;		/* list of PASSING clause arguments, if any */
 	int			location;		/* token location, or -1 if unknown */

src/include/nodes/primnodes.h

@@ -1324,7 +1324,7 @@ typedef struct JsonExpr
 	Node	   *formatted_expr;	/* formatted context item expression */
 	JsonCoercion *result_coercion;	/* resulting coercion to RETURNING type */
 	JsonFormat	format;			/* context item format (JSON/JSONB) */
-	Const	   *path_spec;		/* JSON path specification */
+	Node	   *path_spec;		/* JSON path specification expression */
 	JsonPassing	passing;		/* PASSING clause arguments */
 	JsonReturning returning;	/* RETURNING clause type/format info */
 	JsonBehavior on_empty;		/* ON EMPTY behavior */

src/test/regress/expected/jsonb_sqljson.out

@@ -868,3 +868,38 @@ INSERT INTO test_jsonb_constraints VALUES ('{"a": 10}', 1);
 ERROR:  new row for relation "test_jsonb_constraints" violates check constraint "test_jsonb_constraint4"
 DETAIL:  Failing row contains ({"a": 10}, 1, [1, 2]).
 DROP TABLE test_jsonb_constraints;
+-- Extension: non-constant JSON path
+SELECT JSON_EXISTS(jsonb '{"a": 123}', '$' || '.' || 'a');
+ json_exists 
+-------------
+ t
+(1 row)
+
+SELECT JSON_VALUE(jsonb '{"a": 123}', '$' || '.' || 'a');
+ json_value 
+------------
+ 123
+(1 row)
+
+SELECT JSON_VALUE(jsonb '{"a": 123}', '$' || '.' || 'b' DEFAULT 'foo' ON EMPTY);
+ json_value 
+------------
+ foo
+(1 row)
+
+SELECT JSON_QUERY(jsonb '{"a": 123}', '$' || '.' || 'a');
+ json_query 
+------------
+ 123
+(1 row)
+
+SELECT JSON_QUERY(jsonb '{"a": 123}', '$' || '.' || 'a' WITH WRAPPER);
+ json_query 
+------------
+ [123]
+(1 row)
+
+-- Should fail (invalid path)
+SELECT JSON_QUERY(jsonb '{"a": 123}', 'error' || ' ' || 'error');
+ERROR:  bad jsonpath representation
+DETAIL:  syntax error, unexpected IDENT_P at or near " "

src/test/regress/sql/jsonb_sqljson.sql

@@ -264,3 +264,12 @@ INSERT INTO test_jsonb_constraints VALUES ('{"a": 7}', 1);
 INSERT INTO test_jsonb_constraints VALUES ('{"a": 10}', 1);
 
 DROP TABLE test_jsonb_constraints;
+
+-- Extension: non-constant JSON path
+SELECT JSON_EXISTS(jsonb '{"a": 123}', '$' || '.' || 'a');
+SELECT JSON_VALUE(jsonb '{"a": 123}', '$' || '.' || 'a');
+SELECT JSON_VALUE(jsonb '{"a": 123}', '$' || '.' || 'b' DEFAULT 'foo' ON EMPTY);
+SELECT JSON_QUERY(jsonb '{"a": 123}', '$' || '.' || 'a');
+SELECT JSON_QUERY(jsonb '{"a": 123}', '$' || '.' || 'a' WITH WRAPPER);
+-- Should fail (invalid path)
+SELECT JSON_QUERY(jsonb '{"a": 123}', 'error' || ' ' || 'error');