Revert cascading of JSON_TABLE's ON ERROR

86ab7f4c72 commit made the table-level ON ERROR clause serve as the default
ON ERROR for columns lacking their own, so that a top-level ERROR ON ERROR
turned per-column evaluation errors into hard errors.

The SQL standard does mandate this cascade, but introducing it should be
a deliberate, separately-documented change, so restore the previous
behavior for now.  This also reverts the paired ruleutils.c logic that
deparsed a column's behavior against an ERROR default: that dropped an
explicit ERROR ON EMPTY from a dumped view, and otherwise emitted a
redundant NULL ON EMPTY.

Reported-by: Thom Brown <thom@linux.com>
Discussion: https://postgr.es/m/CAA-aLv7aZGSExnbjJRw8eKkoXbu34TdoKLLA2gPye3aHjO5OSA@mail.gmail.com

src/backend/parser/parse_jsontable.c

@@ -49,8 +49,7 @@ static JsonTablePlan *transformJsonTableNestedColumns(JsonTableParseContext *cxt
 													  List *columns);
 static JsonFuncExpr *transformJsonTableColumn(JsonTableColumn *jtc,
 											  Node *contextItemExpr,
-											  List *passingArgs,
-											  bool errorOnError);
+											  List *passingArgs);
 static bool isCompositeType(Oid typid);
 static JsonTablePlan *makeJsonTablePathScan(JsonTableParseContext *cxt,
 											JsonTablePathSpec *pathspec,
@@ -363,12 +362,8 @@ appendJsonTableColumns(JsonTableParseContext *cxt, List *columns, List *passingA
 {
 	ListCell   *col;
 	ParseState *pstate = cxt->pstate;
-	JsonTable  *jt = cxt->jt;
 	TableFunc  *tf = cxt->tf;
 	bool		ordinality_found = false;
-	JsonBehavior *on_error = jt->on_error;
-	bool		errorOnError = on_error &&
-		on_error->btype == JSON_BEHAVIOR_ERROR;
 	Oid			contextItemTypid = exprType(tf->docexpr);
 
 	foreach(col, columns)
@@ -427,7 +422,7 @@ appendJsonTableColumns(JsonTableParseContext *cxt, List *columns, List *passingA
 					param->typeMod = -1;
 
 					jfe = transformJsonTableColumn(rawc, (Node *) param,
-												   passingArgs, errorOnError);
+												   passingArgs);
 
 					colexpr = transformExpr(pstate, (Node *) jfe,
 											EXPR_KIND_FROM_FUNCTION);
@@ -482,7 +477,7 @@ isCompositeType(Oid typid)
  */
 static JsonFuncExpr *
 transformJsonTableColumn(JsonTableColumn *jtc, Node *contextItemExpr,
-						 List *passingArgs, bool errorOnError)
+						 List *passingArgs)
 {
 	Node	   *pathspec;
 	JsonFuncExpr *jfexpr = makeNode(JsonFuncExpr);
@@ -524,8 +519,6 @@ transformJsonTableColumn(JsonTableColumn *jtc, Node *contextItemExpr,
 	jfexpr->output->returning->format = jtc->format;
 	jfexpr->on_empty = jtc->on_empty;
 	jfexpr->on_error = jtc->on_error;
-	if (jfexpr->on_error == NULL && errorOnError)
-		jfexpr->on_error = makeJsonBehavior(JSON_BEHAVIOR_ERROR, NULL, -1);
 	jfexpr->quotes = jtc->quotes;
 	jfexpr->wrapper = jtc->wrapper;
 	jfexpr->location = jtc->location;

src/backend/utils/adt/ruleutils.c

@@ -12799,7 +12799,6 @@ get_json_table_columns(TableFunc *tf, JsonTablePathScan *scan,
 					   bool showimplicit)
 {
 	StringInfo	buf = context->buf;
-	JsonExpr   *jexpr = castNode(JsonExpr, tf->docexpr);
 	ListCell   *lc_colname;
 	ListCell   *lc_coltype;
 	ListCell   *lc_coltypmod;
@@ -12879,9 +12878,6 @@ get_json_table_columns(TableFunc *tf, JsonTablePathScan *scan,
 			default_behavior = JSON_BEHAVIOR_NULL;
 		}
 
-		if (jexpr->on_error->btype == JSON_BEHAVIOR_ERROR)
-			default_behavior = JSON_BEHAVIOR_ERROR;
-
 		appendStringInfoString(buf, " PATH ");
 
 		get_json_path_spec(colexpr->path_spec, context, showimplicit);

src/test/regress/expected/sqljson_jsontable.out

@@ -547,6 +547,15 @@ SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int PATH 'strict $.a' ERROR O
 ERROR:  jsonpath member accessor can only be applied to an object
 SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int PATH 'lax $.a' ERROR ON EMPTY) ERROR ON ERROR) jt;
 ERROR:  no SQL/JSON item found for specified path of column "a"
+-- Table-level ERROR ON ERROR is not propagated to a column lacking its own
+-- ON ERROR clause: the column keeps the default NULL ON ERROR behavior, so a
+-- conversion failure yields NULL rather than raising an error.
+SELECT * FROM JSON_TABLE(jsonb '"err"', '$' COLUMNS (a int PATH '$') ERROR ON ERROR) jt;
+ a 
+---
+  
+(1 row)
+
 SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a int PATH '$'   DEFAULT 1 ON EMPTY DEFAULT 2 ON ERROR)) jt;
  a 
 ---
@@ -1821,7 +1830,7 @@ CREATE OR REPLACE VIEW public.json_table_view9 AS
    FROM JSON_TABLE(
             '"a"'::text, '$' AS json_table_path_0
             COLUMNS (
-                a text PATH '$' NULL ON EMPTY
+                a text PATH '$'
             ) ERROR ON ERROR
         )
 DROP VIEW json_table_view8, json_table_view9;
@@ -1847,3 +1856,19 @@ CREATE OR REPLACE VIEW public.json_table_view9 AS
             )
         )
 DROP VIEW json_table_view8, json_table_view9;
+-- Test JSON_TABLE() column deparsing -- a non-default ON EMPTY behavior of a
+-- column must be preserved
+CREATE VIEW json_table_view_on_empty AS
+SELECT * FROM JSON_TABLE(jsonb '{}', '$' AS p0
+	COLUMNS (a int PATH '$.nosuch' ERROR ON EMPTY)
+	ERROR ON ERROR);
+\sv json_table_view_on_empty;
+CREATE OR REPLACE VIEW public.json_table_view_on_empty AS
+ SELECT a
+   FROM JSON_TABLE(
+            '{}'::jsonb, '$' AS p0
+            COLUMNS (
+                a integer PATH '$."nosuch"' ERROR ON EMPTY
+            ) ERROR ON ERROR
+        )
+DROP VIEW json_table_view_on_empty;

src/test/regress/sql/sqljson_jsontable.sql

@@ -266,6 +266,11 @@ SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int PATH '$.a' ERROR ON EMPTY
 SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int PATH 'strict $.a' ERROR ON ERROR) ERROR ON ERROR) jt;
 SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int PATH 'lax $.a' ERROR ON EMPTY) ERROR ON ERROR) jt;
 
+-- Table-level ERROR ON ERROR is not propagated to a column lacking its own
+-- ON ERROR clause: the column keeps the default NULL ON ERROR behavior, so a
+-- conversion failure yields NULL rather than raising an error.
+SELECT * FROM JSON_TABLE(jsonb '"err"', '$' COLUMNS (a int PATH '$') ERROR ON ERROR) jt;
+
 SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a int PATH '$'   DEFAULT 1 ON EMPTY DEFAULT 2 ON ERROR)) jt;
 SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a int PATH 'strict $.a' DEFAULT 1 ON EMPTY DEFAULT 2 ON ERROR)) jt;
 SELECT * FROM JSON_TABLE(jsonb '"a"', '$' COLUMNS (a int PATH 'lax $.a' DEFAULT 1 ON EMPTY DEFAULT 2 ON ERROR)) jt;
@@ -1004,3 +1009,13 @@ CREATE VIEW json_table_view9 AS SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a t
 \sv json_table_view9;
 
 DROP VIEW json_table_view8, json_table_view9;
+
+-- Test JSON_TABLE() column deparsing -- a non-default ON EMPTY behavior of a
+-- column must be preserved
+CREATE VIEW json_table_view_on_empty AS
+SELECT * FROM JSON_TABLE(jsonb '{}', '$' AS p0
+	COLUMNS (a int PATH '$.nosuch' ERROR ON EMPTY)
+	ERROR ON ERROR);
+\sv json_table_view_on_empty;
+
+DROP VIEW json_table_view_on_empty;