Re: jsonb_set() strictness considered harmful to data

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 57a1539506..7adb6a2d04 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12203,6 +12203,9 @@ table2-mapping
   <indexterm>
    <primary>jsonb_set</primary>
   </indexterm>
+  <indexterm>
+   <primary>jsonb_set_lax</primary>
+  </indexterm>
   <indexterm>
    <primary>jsonb_insert</primary>
   </indexterm>
@@ -12517,6 +12520,26 @@ table2-mapping
          </para><para><literal>[{"f1": 1, "f2": null, "f3": [2, 3, 4]}, 2]</literal>
         </para></entry>
        </row>
+      <row>
+       <entry><para><literal>jsonb_set_lax(target jsonb, path text[], new_value jsonb <optional>, create_missing boolean</optional> <optional>, null_value_treatment text</optional>)</literal>
+         </para></entry>
+       <entry><para><type>jsonb</type></para></entry>
+       <entry>
+        If <replaceable>new_value</replaceable> is not <literal>null</literal>,
+        behaves identically to <literal>jsonb_set</literal>. Otherwise behaves
+        according to the value of <replaceable>null_value_treatment</replaceable>
+        which must be one of <literal>'raise_exception'</literal>,
+        <literal>'use_json_null'</literal>, <literal>'delete_key'</literal>, or
+        <literal>'return_target'</literal>. The default is
+        <literal>'use_json_null'</literal>.
+       </entry>
+       <entry><para><literal>jsonb_set_lax('[{"f1":1,"f2":null},2,null,3]', '{0,f1}',null)</literal>
+         </para><para><literal>jsonb_set_lax('[{"f1":99,"f2":null},2]', '{0,f3}',null, true, 'return_target')</literal>
+         </para></entry>
+       <entry><para><literal>[{"f1":null,"f2":null},2,null,3]</literal>
+         </para><para><literal>[{"f1": 99, "f2": null}, 2]</literal>
+        </para></entry>
+       </row>
       <row>
        <entry>
            <para><literal>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 2fc3e3ff90..1cb2af1bcd 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1237,6 +1237,15 @@ LANGUAGE INTERNAL
 STRICT IMMUTABLE PARALLEL SAFE
 AS 'jsonb_set';
 
+CREATE OR REPLACE FUNCTION
+  jsonb_set_lax(jsonb_in jsonb, path text[] , replacement jsonb,
+            create_if_missing boolean DEFAULT true,
+            null_value_treatment text DEFAULT 'use_json_null')
+RETURNS jsonb
+LANGUAGE INTERNAL
+CALLED ON NULL INPUT IMMUTABLE PARALLEL SAFE
+AS 'jsonb_set_lax';
+
 CREATE OR REPLACE FUNCTION
   parse_ident(str text, strict boolean DEFAULT true)
 RETURNS text[]
diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index ab5a24a858..b5fa4e7d18 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -4395,6 +4395,70 @@ jsonb_set(PG_FUNCTION_ARGS)
 }
 
 
+/*
+ * SQL function jsonb_set_lax(jsonb, text[], jsonb, boolean, text)
+ */
+Datum
+jsonb_set_lax(PG_FUNCTION_ARGS)
+{
+	/* Jsonb	   *in = PG_GETARG_JSONB_P(0); */
+	/* ArrayType  *path = PG_GETARG_ARRAYTYPE_P(1); */
+	/* Jsonb	  *newval = PG_GETARG_JSONB_P(2); */
+	/* bool		create = PG_GETARG_BOOL(3); */
+	text       *handle_null;
+	char       *handle_val;
+
+	if (PG_ARGISNULL(0) || PG_ARGISNULL(1) || PG_ARGISNULL(3))
+		PG_RETURN_NULL();
+
+	/* could happen if they pass in an explicit NULL */
+	if (PG_ARGISNULL(4))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("need delete_key, return_target, use_json_null, or raise_exception")));
+
+	/* if the new value isn't an SQL NULL just call jsonb_set */
+	if (! PG_ARGISNULL(2))
+		return jsonb_set(fcinfo);
+
+	handle_null = PG_GETARG_TEXT_P(4);
+	handle_val = text_to_cstring(handle_null);
+
+	if (strcmp(handle_val,"raise_exception") == 0)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("NULL is not allowed"),
+				 errdetail("exception raised due to \"null_value_treatment := 'raise_exception'\""),
+				 errhint("to avoid, either change the null_value_treatment argument or ensure that an SQL NULL is not used")));
+	}
+	else if (strcmp(handle_val, "use_json_null") == 0)
+	{
+		Datum	  newval;
+
+		newval = DirectFunctionCall1(jsonb_in, CStringGetDatum("null"));
+
+		fcinfo->args[2].value = newval;
+		fcinfo->args[2].isnull = false;
+		return jsonb_set(fcinfo);
+	}
+	else if (strcmp(handle_val, "delete_key") == 0)
+	{
+		return jsonb_delete_path(fcinfo);
+	}
+	else if (strcmp(handle_val, "return_target") == 0)
+	{
+		Jsonb	   *in = PG_GETARG_JSONB_P(0);
+		PG_RETURN_JSONB_P(in);
+	}
+	else
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("need delete_key, return_target, use_json_null, or raise_exception")));
+	}
+}
+
 /*
  * SQL function jsonb_delete_path(jsonb, text[])
  */
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 0b6045acb1..beb4018f1a 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -9289,6 +9289,9 @@
 { oid => '3304',
   proname => 'jsonb_delete_path', prorettype => 'jsonb',
   proargtypes => 'jsonb _text', prosrc => 'jsonb_delete_path' },
+{ oid => '8945', descr => 'Set part of a jsonb, handle NULL value',
+  proname => 'jsonb_set_lax', prorettype => 'jsonb', proisstrict => 'f',
+  proargtypes => 'jsonb _text jsonb bool text', prosrc => 'jsonb_set_lax' },
 { oid => '3305', descr => 'Set part of a jsonb',
   proname => 'jsonb_set', prorettype => 'jsonb',
   proargtypes => 'jsonb _text jsonb bool', prosrc => 'jsonb_set' },
diff --git a/src/test/regress/expected/jsonb.out b/src/test/regress/expected/jsonb.out
index a2a19f8104..204e021dec 100644
--- a/src/test/regress/expected/jsonb.out
+++ b/src/test/regress/expected/jsonb.out
@@ -4511,6 +4511,63 @@ select jsonb_set('{"a": {"b": [1, 2, 3]}}', '{a, b, non_integer}', '"new_value"'
 ERROR:  path element at position 3 is not an integer: "non_integer"
 select jsonb_set('{"a": {"b": [1, 2, 3]}}', '{a, b, NULL}', '"new_value"');
 ERROR:  path element at position 3 is null
+-- jsonb_set_lax
+\pset null NULL
+-- pass though non nulls to jsonb_set
+select jsonb_set_lax('{"a":1,"b":2}','{b}','5') ;
+  jsonb_set_lax   
+------------------
+ {"a": 1, "b": 5}
+(1 row)
+
+select jsonb_set_lax('{"a":1,"b":2}','{d}','6', true) ;
+      jsonb_set_lax       
+--------------------------
+ {"a": 1, "b": 2, "d": 6}
+(1 row)
+
+-- using the default treatment
+select jsonb_set_lax('{"a":1,"b":2}','{b}',null);
+    jsonb_set_lax    
+---------------------
+ {"a": 1, "b": null}
+(1 row)
+
+select jsonb_set_lax('{"a":1,"b":2}','{d}',null,true);
+        jsonb_set_lax        
+-----------------------------
+ {"a": 1, "b": 2, "d": null}
+(1 row)
+
+-- errors
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, true, null);
+ERROR:  need delete_key, return_target, use_json_null, or raise_exception
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, true, 'no_such_treatment');
+ERROR:  need delete_key, return_target, use_json_null, or raise_exception
+-- explicit treatments
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment := 'raise_exception') as raise_exception;
+ERROR:  NULL is not allowed
+DETAIL:  exception raised due to "null_value_treatment := 'raise_exception'"
+HINT:  to avoid, either change the null_value_treatment argument or ensure that an SQL NULL is not used
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment := 'return_target') as return_target;
+  return_target   
+------------------
+ {"a": 1, "b": 2}
+(1 row)
+
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment := 'delete_key') as delete_key;
+ delete_key 
+------------
+ {"a": 1}
+(1 row)
+
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment := 'use_json_null') as use_json_null;
+    use_json_null    
+---------------------
+ {"a": 1, "b": null}
+(1 row)
+
+\pset null
 -- jsonb_insert
 select jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"');
          jsonb_insert          
diff --git a/src/test/regress/sql/jsonb.sql b/src/test/regress/sql/jsonb.sql
index efd4c45185..bda9cb8a18 100644
--- a/src/test/regress/sql/jsonb.sql
+++ b/src/test/regress/sql/jsonb.sql
@@ -1153,6 +1153,26 @@ select jsonb_set('{"a": [1, 2, 3]}', '{a, non_integer}', '"new_value"');
 select jsonb_set('{"a": {"b": [1, 2, 3]}}', '{a, b, non_integer}', '"new_value"');
 select jsonb_set('{"a": {"b": [1, 2, 3]}}', '{a, b, NULL}', '"new_value"');
 
+-- jsonb_set_lax
+
+\pset null NULL
+
+-- pass though non nulls to jsonb_set
+select jsonb_set_lax('{"a":1,"b":2}','{b}','5') ;
+select jsonb_set_lax('{"a":1,"b":2}','{d}','6', true) ;
+-- using the default treatment
+select jsonb_set_lax('{"a":1,"b":2}','{b}',null);
+select jsonb_set_lax('{"a":1,"b":2}','{d}',null,true);
+-- errors
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, true, null);
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, true, 'no_such_treatment');
+-- explicit treatments
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment := 'raise_exception') as raise_exception;
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment := 'return_target') as return_target;
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment := 'delete_key') as delete_key;
+select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment := 'use_json_null') as use_json_null;
+
+\pset null
 
 -- jsonb_insert
 select jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"');