SQL/JSON: Fix JSON_TABLE() column deparsing

The deparsing code in get_json_expr_options() unnecessarily emitted
the default column-specific ON ERROR / EMPTY behavior when the
top-level ON ERROR behavior in JSON_TABLE was set to ERROR. Fix that
by not overriding the column-specific default, determined based on
the column's JsonExprOp in get_json_table_columns(), with
JSON_BEHAVIOR_ERROR when that is the top-level ON ERROR behavior.

Note that this only removes redundancy; the current deparsing output
is not incorrect, just redundant.

Reviewed-by: Jian He <jian.universality@gmail.com>
Discussion: https://postgr.es/m/CACJufxEo4sUjKCYtda0_qt9tazqqKPmF1cqhW9KBOUeJFqQd2g@mail.gmail.com
Backpatch-through: 17

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index b31be31321dc3c6bbc36a5be8e8495e835c4cea3..371b46e7a2d92080f268d92189873ed4be9f79ff 100644 (file)
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11719,7 +11719,6 @@ 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;
@@ -11772,6 +11771,10 @@ get_json_table_columns(TableFunc *tf, JsonTablePathScan *scan,
                if (ordinality)
                        continue;
 
+               /*
+                * Set default_behavior to guide get_json_expr_options() on whether to
+                * to emit the ON ERROR / EMPTY clauses.
+                */
                if (colexpr->op == JSON_EXISTS_OP)
                {
                        appendStringInfoString(buf, " EXISTS");
@@ -11795,9 +11798,6 @@ 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);

diff --git a/src/test/regress/expected/sqljson_jsontable.out b/src/test/regress/expected/sqljson_jsontable.out
index 721e01d6ad079802a650a9c3e47563da346b4649..ebfde38a056810a002ea619d4488ef6fa3a33343 100644 (file)
--- a/src/test/regress/expected/sqljson_jsontable.out
+++ b/src/test/regress/expected/sqljson_jsontable.out
@@ -1132,3 +1132,21 @@ ERROR:  invalid ON ERROR behavior for column "a"
 LINE 1: ...M JSON_TABLE(jsonb '1', '$' COLUMNS (a int exists empty obje...
                                                              ^
 DETAIL:  Only ERROR, TRUE, FALSE, or UNKNOWN is allowed in ON ERROR for EXISTS columns.
+-- Test JSON_TABLE() column deparsing -- don't emit default ON ERROR / EMPTY
+-- behavior
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$'));
+                                             QUERY PLAN                                              
+-----------------------------------------------------------------------------------------------------
+ Table Function Scan on "json_table"  (cost=0.01..1.00 rows=100 width=32)
+   Output: a
+   Table Function Call: JSON_TABLE('"a"'::jsonb, '$' AS json_table_path_0 COLUMNS (a text PATH '$'))
+(3 rows)
+
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') ERROR ON ERROR);
+                                                     QUERY PLAN                                                     
+--------------------------------------------------------------------------------------------------------------------
+ Table Function Scan on "json_table"  (cost=0.01..1.00 rows=100 width=32)
+   Output: a
+   Table Function Call: JSON_TABLE('"a"'::jsonb, '$' AS json_table_path_0 COLUMNS (a text PATH '$') ERROR ON ERROR)
+(3 rows)
+

diff --git a/src/test/regress/sql/sqljson_jsontable.sql b/src/test/regress/sql/sqljson_jsontable.sql
index 38992316f5afeb28947bce8879840364e9895e16..c94088789260fe11f97cf04c6285e59317476f3e 100644 (file)
--- a/src/test/regress/sql/sqljson_jsontable.sql
+++ b/src/test/regress/sql/sqljson_jsontable.sql
@@ -542,3 +542,8 @@ SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int) NULL ON ERROR);
 SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int true on empty));
 SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int omit quotes true on error));
 SELECT * FROM JSON_TABLE(jsonb '1', '$' COLUMNS (a int exists empty object on error));
+
+-- Test JSON_TABLE() column deparsing -- don't emit default ON ERROR / EMPTY
+-- behavior
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$'));
+EXPLAIN VERBOSE SELECT * from JSON_TABLE('"a"', '$' COLUMNS (a text PATH '$') ERROR ON ERROR);