2 files changed, 698 insertions, 51 deletions

diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
index acd3ea61344..1c364a7f4c5 100644
--- a/src/backend/executor/execExpr.c
+++ b/src/backend/executor/execExpr.c
@@ -47,6 +47,7 @@
 #include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/datum.h"
+#include "utils/jsonpath.h"
 #include "utils/lsyscache.h"
 #include "utils/typcache.h"
 
@@ -85,6 +86,40 @@ static void ExecBuildAggTransCall(ExprState *state, AggState *aggstate,
 								  bool nullcheck);
 
 
+static ExprState *
+ExecInitExprInternal(Expr *node, PlanState *parent, ParamListInfo ext_params,
+					 Datum *caseval, bool *casenull)
+{
+	ExprState  *state;
+	ExprEvalStep scratch = {0};
+
+	/* Special case: NULL expression produces a NULL ExprState pointer */
+	if (node == NULL)
+		return NULL;
+
+	/* Initialize ExprState with empty step list */
+	state = makeNode(ExprState);
+	state->expr = node;
+	state->parent = parent;
+	state->ext_params = ext_params;
+	state->innermost_caseval = caseval;
+	state->innermost_casenull = casenull;
+
+	/* Insert EEOP_*_FETCHSOME steps as needed */
+	ExecInitExprSlots(state, (Node *) node);
+
+	/* Compile the expression proper */
+	ExecInitExprRec(node, state, &state->resvalue, &state->resnull);
+
+	/* Finally, append a DONE step */
+	scratch.opcode = EEOP_DONE;
+	ExprEvalPushStep(state, &scratch);
+
+	ExecReadyExpr(state);
+
+	return state;
+}
+
 /*
  * ExecInitExpr: prepare an expression tree for execution
  *
@@ -122,32 +157,7 @@ static void ExecBuildAggTransCall(ExprState *state, AggState *aggstate,
 ExprState *
 ExecInitExpr(Expr *node, PlanState *parent)
 {
-	ExprState  *state;
-	ExprEvalStep scratch = {0};
-
-	/* Special case: NULL expression produces a NULL ExprState pointer */
-	if (node == NULL)
-		return NULL;
-
-	/* Initialize ExprState with empty step list */
-	state = makeNode(ExprState);
-	state->expr = node;
-	state->parent = parent;
-	state->ext_params = NULL;
-
-	/* Insert EEOP_*_FETCHSOME steps as needed */
-	ExecInitExprSlots(state, (Node *) node);
-
-	/* Compile the expression proper */
-	ExecInitExprRec(node, state, &state->resvalue, &state->resnull);
-
-	/* Finally, append a DONE step */
-	scratch.opcode = EEOP_DONE;
-	ExprEvalPushStep(state, &scratch);
-
-	ExecReadyExpr(state);
-
-	return state;
+	return ExecInitExprInternal(node, parent, NULL, NULL, NULL);
 }
 
 /*
@@ -159,32 +169,20 @@ ExecInitExpr(Expr *node, PlanState *parent)
 ExprState *
 ExecInitExprWithParams(Expr *node, ParamListInfo ext_params)
 {
-	ExprState  *state;
-	ExprEvalStep scratch = {0};
-
-	/* Special case: NULL expression produces a NULL ExprState pointer */
-	if (node == NULL)
-		return NULL;
-
-	/* Initialize ExprState with empty step list */
-	state = makeNode(ExprState);
-	state->expr = node;
-	state->parent = NULL;
-	state->ext_params = ext_params;
-
-	/* Insert EEOP_*_FETCHSOME steps as needed */
-	ExecInitExprSlots(state, (Node *) node);
-
-	/* Compile the expression proper */
-	ExecInitExprRec(node, state, &state->resvalue, &state->resnull);
-
-	/* Finally, append a DONE step */
-	scratch.opcode = EEOP_DONE;
-	ExprEvalPushStep(state, &scratch);
-
-	ExecReadyExpr(state);
+	return ExecInitExprInternal(node, NULL, ext_params, NULL, NULL);
+}
 
-	return state;
+/*
+ * ExecInitExprWithCaseValue: prepare an expression tree for execution
+ *
+ * This is the same as ExecInitExpr, except that a pointer to the value for
+ * CasTestExpr is passed here.
+ */
+ExprState *
+ExecInitExprWithCaseValue(Expr *node, PlanState *parent,
+						  Datum *caseval, bool *casenull)
+{
+	return ExecInitExprInternal(node, parent, NULL, caseval, casenull);
 }
 
 /*
@@ -2526,6 +2524,112 @@ ExecInitExprRec(Expr *node, ExprState *state,
 				break;
 			}
 
+		case T_JsonExpr:
+			{
+				JsonExpr   *jexpr = castNode(JsonExpr, node);
+				ListCell   *argexprlc;
+				ListCell   *argnamelc;
+
+				scratch.opcode = EEOP_JSONEXPR;
+				scratch.d.jsonexpr.jsexpr = jexpr;
+
+				scratch.d.jsonexpr.formatted_expr =
+					palloc(sizeof(*scratch.d.jsonexpr.formatted_expr));
+
+				ExecInitExprRec((Expr *) jexpr->formatted_expr, state,
+								&scratch.d.jsonexpr.formatted_expr->value,
+								&scratch.d.jsonexpr.formatted_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.res_expr =
+					palloc(sizeof(*scratch.d.jsonexpr.res_expr));
+
+				scratch.d.jsonexpr.result_expr = jexpr->result_coercion
+					? ExecInitExprWithCaseValue((Expr *) jexpr->result_coercion->expr,
+												state->parent,
+												&scratch.d.jsonexpr.res_expr->value,
+												&scratch.d.jsonexpr.res_expr->isnull)
+					: NULL;
+
+				scratch.d.jsonexpr.default_on_empty = !jexpr->on_empty ? NULL :
+					ExecInitExpr((Expr *) jexpr->on_empty->default_expr,
+								 state->parent);
+
+				scratch.d.jsonexpr.default_on_error =
+					ExecInitExpr((Expr *) jexpr->on_error->default_expr,
+								 state->parent);
+
+				if (jexpr->omit_quotes ||
+					(jexpr->result_coercion && jexpr->result_coercion->via_io))
+				{
+					Oid			typinput;
+
+					/* lookup the result type's input function */
+					getTypeInputInfo(jexpr->returning->typid, &typinput,
+									 &scratch.d.jsonexpr.input.typioparam);
+					fmgr_info(typinput, &scratch.d.jsonexpr.input.func);
+				}
+
+				scratch.d.jsonexpr.args = NIL;
+
+				forboth(argexprlc, jexpr->passing_values,
+						argnamelc, jexpr->passing_names)
+				{
+					Expr	   *argexpr = (Expr *) lfirst(argexprlc);
+					String	   *argname = lfirst_node(String, argnamelc);
+					JsonPathVariableEvalContext *var = palloc(sizeof(*var));
+
+					var->name = pstrdup(argname->sval);
+					var->typid = exprType((Node *) argexpr);
+					var->typmod = exprTypmod((Node *) argexpr);
+					var->estate = ExecInitExpr(argexpr, state->parent);
+					var->econtext = NULL;
+					var->evaluated = false;
+					var->value = (Datum) 0;
+					var->isnull = true;
+
+					scratch.d.jsonexpr.args =
+						lappend(scratch.d.jsonexpr.args, var);
+				}
+
+				scratch.d.jsonexpr.cache = NULL;
+
+				if (jexpr->coercions)
+				{
+					JsonCoercion **coercion;
+					struct JsonCoercionState *cstate;
+					Datum	   *caseval;
+					bool	   *casenull;
+
+					scratch.d.jsonexpr.coercion_expr =
+						palloc(sizeof(*scratch.d.jsonexpr.coercion_expr));
+
+					caseval = &scratch.d.jsonexpr.coercion_expr->value;
+					casenull = &scratch.d.jsonexpr.coercion_expr->isnull;
+
+					for (cstate = &scratch.d.jsonexpr.coercions.null,
+						 coercion = &jexpr->coercions->null;
+						 coercion <= &jexpr->coercions->composite;
+						 coercion++, cstate++)
+					{
+						cstate->coercion = *coercion;
+						cstate->estate = *coercion ?
+							ExecInitExprWithCaseValue((Expr *)(*coercion)->expr,
+													  state->parent,
+													  caseval, casenull) : NULL;
+					}
+				}
+
+				ExprEvalPushStep(state, &scratch);
+				break;
+			}
+
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index c0bd9556209..1215f707e28 100644
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -57,14 +57,18 @@
 #include "postgres.h"
 
 #include "access/heaptoast.h"
+#include "access/xact.h"
+#include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
 #include "commands/sequence.h"
 #include "executor/execExpr.h"
 #include "executor/nodeSubplan.h"
 #include "funcapi.h"
 #include "miscadmin.h"
+#include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "parser/parsetree.h"
+#include "parser/parse_expr.h"
 #include "pgstat.h"
 #include "utils/array.h"
 #include "utils/builtins.h"
@@ -74,8 +78,10 @@
 #include "utils/json.h"
 #include "utils/jsonb.h"
 #include "utils/jsonfuncs.h"
+#include "utils/jsonpath.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
+#include "utils/resowner.h"
 #include "utils/timestamp.h"
 #include "utils/typcache.h"
 #include "utils/xml.h"
@@ -482,6 +488,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		&&CASE_EEOP_SUBPLAN,
 		&&CASE_EEOP_JSON_CONSTRUCTOR,
 		&&CASE_EEOP_IS_JSON,
+		&&CASE_EEOP_JSONEXPR,
 		&&CASE_EEOP_AGG_STRICT_DESERIALIZE,
 		&&CASE_EEOP_AGG_DESERIALIZE,
 		&&CASE_EEOP_AGG_STRICT_INPUT_CHECK_ARGS,
@@ -1805,7 +1812,13 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		{
 			/* too complex for an inline implementation */
 			ExecEvalJsonIsPredicate(state, op);
+			EEO_NEXT();
+		}
 
+		EEO_CASE(EEOP_JSONEXPR)
+		{
+			/* too complex for an inline implementation */
+			ExecEvalJson(state, op, econtext);
 			EEO_NEXT();
 		}
 
@@ -4523,3 +4536,533 @@ ExecEvalJsonConstructor(ExprState *state, ExprEvalStep *op,
 	*op->resvalue = res;
 	*op->resnull = isnull;
 }
+
+/*
+ * Evaluate a JSON error/empty behavior result.
+ */
+static Datum
+ExecEvalJsonBehavior(ExprContext *econtext, JsonBehavior *behavior,
+					 ExprState *default_estate, bool *is_null)
+{
+	*is_null = false;
+
+	switch (behavior->btype)
+	{
+		case JSON_BEHAVIOR_EMPTY_ARRAY:
+			return JsonbPGetDatum(JsonbMakeEmptyArray());
+
+		case JSON_BEHAVIOR_EMPTY_OBJECT:
+			return JsonbPGetDatum(JsonbMakeEmptyObject());
+
+		case JSON_BEHAVIOR_TRUE:
+			return BoolGetDatum(true);
+
+		case JSON_BEHAVIOR_FALSE:
+			return BoolGetDatum(false);
+
+		case JSON_BEHAVIOR_NULL:
+		case JSON_BEHAVIOR_UNKNOWN:
+			*is_null = true;
+			return (Datum) 0;
+
+		case JSON_BEHAVIOR_DEFAULT:
+			return ExecEvalExpr(default_estate, econtext, is_null);
+
+		default:
+			elog(ERROR, "unrecognized SQL/JSON behavior %d", behavior->btype);
+			return (Datum) 0;
+	}
+}
+
+/*
+ * Evaluate a coercion of a JSON item to the target type.
+ */
+static Datum
+ExecEvalJsonExprCoercion(ExprEvalStep *op, ExprContext *econtext,
+						 Datum res, bool *isNull, void *p, bool *error)
+{
+	ExprState *estate = p;
+
+	if (estate)		/* coerce using specified expression */
+		return ExecEvalExpr(estate, econtext, isNull);
+
+	if (op->d.jsonexpr.jsexpr->op != JSON_EXISTS_OP)
+	{
+		JsonCoercion *coercion = op->d.jsonexpr.jsexpr->result_coercion;
+		JsonExpr   *jexpr = op->d.jsonexpr.jsexpr;
+		Jsonb	   *jb = *isNull ? NULL : DatumGetJsonbP(res);
+
+		if ((coercion && coercion->via_io) ||
+			(jexpr->omit_quotes && !*isNull &&
+			 JB_ROOT_IS_SCALAR(jb)))
+		{
+			/* strip quotes and call typinput function */
+			char	   *str = *isNull ? NULL : JsonbUnquote(jb);
+
+			return InputFunctionCall(&op->d.jsonexpr.input.func, str,
+									 op->d.jsonexpr.input.typioparam,
+									 jexpr->returning->typmod);
+		}
+		else if (coercion && coercion->via_populate)
+			return json_populate_type(res, JSONBOID,
+									  jexpr->returning->typid,
+									  jexpr->returning->typmod,
+									  &op->d.jsonexpr.cache,
+									  econtext->ecxt_per_query_memory,
+									  isNull);
+	}
+
+	if (op->d.jsonexpr.result_expr)
+	{
+		op->d.jsonexpr.res_expr->value = res;
+		op->d.jsonexpr.res_expr->isnull = *isNull;
+
+		res = ExecEvalExpr(op->d.jsonexpr.result_expr, econtext, isNull);
+	}
+
+	return res;
+}
+
+/*
+ * Evaluate a JSON path variable caching computed value.
+ */
+int
+EvalJsonPathVar(void *cxt, char *varName, int varNameLen,
+				JsonbValue *val, JsonbValue *baseObject)
+{
+	JsonPathVariableEvalContext *var = NULL;
+	List	   *vars = cxt;
+	ListCell   *lc;
+	int			id = 1;
+
+	if (!varName)
+		return list_length(vars);
+
+	foreach(lc, vars)
+	{
+		var = lfirst(lc);
+
+		if (!strncmp(var->name, varName, varNameLen))
+			break;
+
+		var = NULL;
+		id++;
+	}
+
+	if (!var)
+		return -1;
+
+	if (!var->evaluated)
+	{
+		var->value = ExecEvalExpr(var->estate, var->econtext, &var->isnull);
+		var->evaluated = true;
+	}
+
+	if (var->isnull)
+	{
+		val->type = jbvNull;
+		return 0;
+	}
+
+	JsonItemFromDatum(var->value, var->typid, var->typmod, val);
+
+	*baseObject = *val;
+	return id;
+}
+
+/*
+ * Prepare SQL/JSON item coercion to the output type. Returned a datum of the
+ * corresponding SQL type and a pointer to the coercion state.
+ */
+Datum
+ExecPrepareJsonItemCoercion(JsonbValue *item,
+							JsonReturning *returning,
+							struct JsonCoercionsState *coercions,
+							struct JsonCoercionState **pcoercion)
+{
+	struct JsonCoercionState *coercion;
+	Datum		res;
+	JsonbValue	buf;
+
+	if (item->type == jbvBinary &&
+		JsonContainerIsScalar(item->val.binary.data))
+	{
+		bool		res PG_USED_FOR_ASSERTS_ONLY;
+
+		res = JsonbExtractScalar(item->val.binary.data, &buf);
+		item = &buf;
+		Assert(res);
+	}
+
+	/* get coercion state reference and datum of the corresponding SQL type */
+	switch (item->type)
+	{
+		case jbvNull:
+			coercion = &coercions->null;
+			res = (Datum) 0;
+			break;
+
+		case jbvString:
+			coercion = &coercions->string;
+			res = PointerGetDatum(
+				cstring_to_text_with_len(item->val.string.val,
+										 item->val.string.len));
+			break;
+
+		case jbvNumeric:
+			coercion = &coercions->numeric;
+			res = NumericGetDatum(item->val.numeric);
+			break;
+
+		case jbvBool:
+			coercion = &coercions->boolean;
+			res = BoolGetDatum(item->val.boolean);
+			break;
+
+		case jbvDatetime:
+			res = item->val.datetime.value;
+			switch (item->val.datetime.typid)
+			{
+				case DATEOID:
+					coercion = &coercions->date;
+					break;
+				case TIMEOID:
+					coercion = &coercions->time;
+					break;
+				case TIMETZOID:
+					coercion = &coercions->timetz;
+					break;
+				case TIMESTAMPOID:
+					coercion = &coercions->timestamp;
+					break;
+				case TIMESTAMPTZOID:
+					coercion = &coercions->timestamptz;
+					break;
+				default:
+					elog(ERROR, "unexpected jsonb datetime type oid %d",
+						 item->val.datetime.typid);
+					return (Datum) 0;
+			}
+			break;
+
+		case jbvArray:
+		case jbvObject:
+		case jbvBinary:
+			coercion = &coercions->composite;
+			res = JsonbPGetDatum(JsonbValueToJsonb(item));
+			break;
+
+		default:
+			elog(ERROR, "unexpected jsonb value type %d", item->type);
+			return (Datum) 0;
+	}
+
+	*pcoercion = coercion;
+
+	return res;
+}
+
+typedef Datum (*JsonFunc)(ExprEvalStep *op, ExprContext *econtext,
+						  Datum item, bool *resnull, void *p, bool *error);
+
+static Datum
+ExecEvalJsonExprSubtrans(JsonFunc func, ExprEvalStep *op,
+						 ExprContext *econtext,
+						 Datum res, bool *resnull,
+						 void *p, bool *error, bool subtrans)
+{
+	MemoryContext oldcontext;
+	ResourceOwner oldowner;
+
+	if (!subtrans)
+		/* No need to use subtransactions. */
+		return func(op, econtext, res, resnull, p, error);
+
+	/*
+	 * We should catch exceptions of category ERRCODE_DATA_EXCEPTION
+	 * and execute the corresponding ON ERROR behavior then.
+	 */
+	oldcontext = CurrentMemoryContext;
+	oldowner = CurrentResourceOwner;
+
+	Assert(error);
+
+	BeginInternalSubTransaction(NULL);
+	/* Want to execute expressions inside function's memory context */
+	MemoryContextSwitchTo(oldcontext);
+
+	PG_TRY();
+	{
+		res = func(op, econtext, res, resnull, p, error);
+
+		/* Commit the inner transaction, return to outer xact context */
+		ReleaseCurrentSubTransaction();
+		MemoryContextSwitchTo(oldcontext);
+		CurrentResourceOwner = oldowner;
+	}
+	PG_CATCH();
+	{
+		ErrorData  *edata;
+
+		/* Save error info in oldcontext */
+		MemoryContextSwitchTo(oldcontext);
+		edata = CopyErrorData();
+		FlushErrorState();
+
+		/* Abort the inner transaction */
+		RollbackAndReleaseCurrentSubTransaction();
+		MemoryContextSwitchTo(oldcontext);
+		CurrentResourceOwner = oldowner;
+
+		if (ERRCODE_TO_CATEGORY(edata->sqlerrcode) !=
+			ERRCODE_DATA_EXCEPTION)
+			ReThrowError(edata);
+
+		res = (Datum) 0;
+		*error = true;
+	}
+	PG_END_TRY();
+
+	return res;
+}
+
+
+typedef struct
+{
+	JsonPath   *path;
+	bool	   *error;
+	bool		coercionInSubtrans;
+} ExecEvalJsonExprContext;
+
+static Datum
+ExecEvalJsonExpr(ExprEvalStep *op, ExprContext *econtext,
+				 Datum item, bool *resnull, void *pcxt,
+				 bool *error)
+{
+	ExecEvalJsonExprContext *cxt = pcxt;
+	JsonPath   *path = cxt->path;
+	JsonExpr   *jexpr = op->d.jsonexpr.jsexpr;
+	ExprState  *estate = NULL;
+	bool		empty = false;
+	Datum		res = (Datum) 0;
+
+	switch (jexpr->op)
+	{
+		case JSON_QUERY_OP:
+			res = JsonPathQuery(item, path, jexpr->wrapper, &empty, error,
+								op->d.jsonexpr.args);
+			if (error && *error)
+			{
+				*resnull = true;
+				return (Datum) 0;
+			}
+			*resnull = !DatumGetPointer(res);
+			break;
+
+		case JSON_VALUE_OP:
+			{
+				struct JsonCoercionState *jcstate;
+				JsonbValue *jbv = JsonPathValue(item, path, &empty, error,
+												op->d.jsonexpr.args);
+
+				if (error && *error)
+					return (Datum) 0;
+
+				if (!jbv)	/* NULL or empty */
+					break;
+
+				Assert(!empty);
+
+				*resnull = false;
+
+				/* coerce scalar item to the output type */
+				if (jexpr->returning->typid == JSONOID ||
+					jexpr->returning->typid == JSONBOID)
+				{
+					/* Use result coercion from json[b] to the output type */
+					res = JsonbPGetDatum(JsonbValueToJsonb(jbv));
+					break;
+				}
+
+				/* Use coercion from SQL/JSON item type to the output type */
+				res = ExecPrepareJsonItemCoercion(jbv,
+												  op->d.jsonexpr.jsexpr->returning,
+												  &op->d.jsonexpr.coercions,
+												  &jcstate);
+
+				if (jcstate->coercion &&
+					(jcstate->coercion->via_io ||
+					 jcstate->coercion->via_populate))
+				{
+					if (error)
+					{
+						*error = true;
+						return (Datum) 0;
+					}
+					/*
+					 * Coercion via I/O means here that the cast to the target
+					 * type simply does not exist.
+					 */
+					ereport(ERROR,
+							/*
+							 * XXX Standard says about a separate error code
+							 * ERRCODE_SQL_JSON_ITEM_CANNOT_BE_CAST_TO_TARGET_TYPE
+							 * but does not define its number.
+							 */
+							(errcode(ERRCODE_SQL_JSON_SCALAR_REQUIRED),
+							 errmsg("SQL/JSON item cannot be cast to target type")));
+				}
+				else if (!jcstate->estate)
+					return res;		/* no coercion */
+
+				/* coerce using specific expression */
+				estate = jcstate->estate;
+				op->d.jsonexpr.coercion_expr->value = res;
+				op->d.jsonexpr.coercion_expr->isnull = *resnull;
+				break;
+			}
+
+		case JSON_EXISTS_OP:
+			{
+				bool		exists = JsonPathExists(item, path,
+													op->d.jsonexpr.args,
+													error);
+
+				*resnull = error && *error;
+				res = BoolGetDatum(exists);
+
+				if (!op->d.jsonexpr.result_expr)
+					return res;
+
+				/* coerce using result expression */
+				estate = op->d.jsonexpr.result_expr;
+				op->d.jsonexpr.res_expr->value = res;
+				op->d.jsonexpr.res_expr->isnull = *resnull;
+				break;
+			}
+
+		default:
+			elog(ERROR, "unrecognized SQL/JSON expression op %d", jexpr->op);
+			return (Datum) 0;
+	}
+
+	if (empty)
+	{
+		Assert(jexpr->on_empty);	/* it is not JSON_EXISTS */
+
+		if (jexpr->on_empty->btype == JSON_BEHAVIOR_ERROR)
+		{
+			if (error)
+			{
+				*error = true;
+				return (Datum) 0;
+			}
+
+			ereport(ERROR,
+					(errcode(ERRCODE_NO_SQL_JSON_ITEM),
+					 errmsg("no SQL/JSON item")));
+		}
+
+		if (jexpr->on_empty->btype == JSON_BEHAVIOR_DEFAULT)
+			/*
+			 * Execute DEFAULT expression as a coercion expression, because
+			 * its result is already coerced to the target type.
+			 */
+			estate = op->d.jsonexpr.default_on_empty;
+		else
+			/* Execute ON EMPTY behavior */
+			res = ExecEvalJsonBehavior(econtext, jexpr->on_empty,
+									   op->d.jsonexpr.default_on_empty,
+									   resnull);
+	}
+
+	return ExecEvalJsonExprSubtrans(ExecEvalJsonExprCoercion, op, econtext,
+									res, resnull, estate, error,
+									cxt->coercionInSubtrans);
+}
+
+bool
+ExecEvalJsonNeedsSubTransaction(JsonExpr *jsexpr,
+								struct JsonCoercionsState *coercions)
+{
+	if (jsexpr->on_error->btype == JSON_BEHAVIOR_ERROR)
+		return false;
+
+	if (jsexpr->op == JSON_EXISTS_OP && !jsexpr->result_coercion)
+		return false;
+
+	if (!coercions)
+		return true;
+
+	return false;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEvalJson
+ * ----------------------------------------------------------------
+ */
+void
+ExecEvalJson(ExprState *state, ExprEvalStep *op, ExprContext *econtext)
+{
+	ExecEvalJsonExprContext cxt;
+	JsonExpr   *jexpr = op->d.jsonexpr.jsexpr;
+	Datum		item;
+	Datum		res = (Datum) 0;
+	JsonPath   *path;
+	ListCell   *lc;
+	bool		error = false;
+	bool		needSubtrans;
+	bool		throwErrors = jexpr->on_error->btype == JSON_BEHAVIOR_ERROR;
+
+	*op->resnull = true;		/* until we get a result */
+	*op->resvalue = (Datum) 0;
+
+	if (op->d.jsonexpr.formatted_expr->isnull || op->d.jsonexpr.pathspec->isnull)
+	{
+		/* execute domain checks for NULLs */
+		(void) ExecEvalJsonExprCoercion(op, econtext, res, op->resnull,
+										NULL, NULL);
+
+		Assert(*op->resnull);
+		return;
+	}
+
+	item = op->d.jsonexpr.formatted_expr->value;
+	path = DatumGetJsonPathP(op->d.jsonexpr.pathspec->value);
+
+	/* reset JSON path variable contexts */
+	foreach(lc, op->d.jsonexpr.args)
+	{
+		JsonPathVariableEvalContext *var = lfirst(lc);
+
+		var->econtext = econtext;
+		var->evaluated = false;
+	}
+
+	needSubtrans = ExecEvalJsonNeedsSubTransaction(jexpr, &op->d.jsonexpr.coercions);
+
+	cxt.path = path;
+	cxt.error = throwErrors ? NULL : &error;
+	cxt.coercionInSubtrans = !needSubtrans && !throwErrors;
+	Assert(!needSubtrans || cxt.error);
+
+	res = ExecEvalJsonExprSubtrans(ExecEvalJsonExpr, op, econtext, item,
+								   op->resnull, &cxt, cxt.error,
+								   needSubtrans);
+
+	if (error)
+	{
+		/* Execute ON ERROR behavior */
+		res = ExecEvalJsonBehavior(econtext, jexpr->on_error,
+								   op->d.jsonexpr.default_on_error,
+								   op->resnull);
+
+		/* result is already coerced in DEFAULT behavior case */
+		if (jexpr->on_error->btype != JSON_BEHAVIOR_DEFAULT)
+			res = ExecEvalJsonExprCoercion(op, econtext, res,
+										   op->resnull,
+										   NULL, NULL);
+	}
+
+	*op->resvalue = res;
+}