MDEV-13992 Implement JSON_MERGE_PATCH.

JSON_MERGE_PATCH implemented. Added JSON_MERGE_PRESERVE as a synonim for
the JSON_MERGE.

mysql-test/r/func_json.result

@@ -306,7 +306,7 @@ select json_merge('string', 123);
 json_merge('string', 123)
 NULL
 Warnings:
-Warning	4038	Syntax error in JSON text in argument 1 to function 'json_merge' at position 1
+Warning	4038	Syntax error in JSON text in argument 1 to function 'json_merge_preserve' at position 1
 select json_merge('"string"', 123);
 json_merge('"string"', 123)
 ["string", 123]
@@ -326,7 +326,7 @@ select json_merge('a','b');
 json_merge('a','b')
 NULL
 Warnings:
-Warning	4038	Syntax error in JSON text in argument 1 to function 'json_merge' at position 1
+Warning	4038	Syntax error in JSON text in argument 1 to function 'json_merge_preserve' at position 1
 select json_merge('{"a":"b"}','{"c":"d"}');
 json_merge('{"a":"b"}','{"c":"d"}')
 {"a": "b", "c": "d"}
@@ -843,5 +843,76 @@ SELECT CHARSET(JSON_OBJECT());
 CHARSET(JSON_OBJECT())
 latin1
 #
+# MDEV-13992 Implement JSON_MERGE_PATCH
+#
+CREATE TABLE merge_t(
+id INT PRIMARY KEY AUTO_INCREMENT,
+target VARCHAR(100), patch VARCHAR(100)
+);
+INSERT INTO merge_t(target, patch) VALUES
+('{"a":"b"}', '{"a":"c"}'),
+('{"a":"b"}', '{"b":"c"}'),
+('{"a":"b"}', '{"a":null}'),
+('{"a":"b", "b":"c"}', '{"a":null}'),
+('{"a":["b"]}', '{"a":"c"}'),
+('{"a":"c"}', '{"a":["b"]}'),
+('{"a": {"b":"c"}}', '{"a": {"b":"d", "c":null}}'),
+('{"a":[{"b":"c"}]}', '{"a": [1]}'),
+('["a","b"]', '["c","d"]'),
+('{"a":"b"}', '["c"]'),
+('{"a":"foo"}', 'null'),
+('{"a":"foo"}', '"bar"'),
+('{"e":null}', '{"a":1}'),
+('[1,2]', '{"a":"b", "c":null}'),
+('{}', '{"a":{"bb":{"ccc":null}}}'),
+(NULL, '{}'),
+('{}', NULL);
+SELECT id, target, patch,
+JSON_MERGE_PATCH(target, patch) AS merged,
+JSON_EXTRACT(JSON_MERGE_PATCH(target, patch), '$.a') AS a
+FROM merge_t ORDER BY id;
+id	target	patch	merged	a
+1	{"a":"b"}	{"a":"c"}	{"a": "c"}	"c"
+2	{"a":"b"}	{"b":"c"}	{"a": "b", "b": "c"}	"b"
+3	{"a":"b"}	{"a":null}	{}	NULL
+4	{"a":"b", "b":"c"}	{"a":null}	{"b": "c"}	NULL
+5	{"a":["b"]}	{"a":"c"}	{"a": "c"}	"c"
+6	{"a":"c"}	{"a":["b"]}	{"a": ["b"]}	["b"]
+7	{"a": {"b":"c"}}	{"a": {"b":"d", "c":null}}	{"a": {"b": "d"}}	{"b": "d"}
+8	{"a":[{"b":"c"}]}	{"a": [1]}	{"a": [1]}	[1]
+9	["a","b"]	["c","d"]	["c", "d"]	NULL
+10	{"a":"b"}	["c"]	["c"]	NULL
+11	{"a":"foo"}	null	null	NULL
+12	{"a":"foo"}	"bar"	"bar"	NULL
+13	{"e":null}	{"a":1}	{"e": null, "a": 1}	1
+14	[1,2]	{"a":"b", "c":null}	{"a": "b"}	"b"
+15	{}	{"a":{"bb":{"ccc":null}}}	{"a": {"bb": {}}}	{"bb": {}}
+16	NULL	{}	NULL	NULL
+17	{}	NULL	NULL	NULL
+DROP TABLE merge_t;
+SELECT JSON_MERGE_PATCH('{"a":"b"}', NULL, '{"c":"d"}');
+JSON_MERGE_PATCH('{"a":"b"}', NULL, '{"c":"d"}')
+NULL
+SELECT JSON_MERGE_PATCH(NULL, '[1,2,3]');
+JSON_MERGE_PATCH(NULL, '[1,2,3]')
+[1, 2, 3]
+SELECT JSON_MERGE_PATCH('{"a":"b"}', NULL, '[1,2,3]', '{"c":null,"d":"e"}');
+JSON_MERGE_PATCH('{"a":"b"}', NULL, '[1,2,3]', '{"c":null,"d":"e"}')
+{"d": "e"}
+SELECT JSON_MERGE_PATCH();
+ERROR 42000: Incorrect parameter count in the call to native function 'JSON_MERGE_PATCH'
+SELECT JSON_MERGE_PATCH('{}');
+ERROR 42000: Incorrect parameter count in the call to native function 'JSON_MERGE_PATCH'
+SELECT JSON_MERGE_PATCH('{', '[1,2,3]');
+JSON_MERGE_PATCH('{', '[1,2,3]')
+NULL
+Warnings:
+Warning	4037	Unexpected end of JSON text in argument 1 to function 'json_merge_patch'
+SELECT JSON_MERGE_PATCH('{"a":"b"}', '[1,');
+JSON_MERGE_PATCH('{"a":"b"}', '[1,')
+NULL
+Warnings:
+Warning	4037	Unexpected end of JSON text in argument 2 to function 'json_merge_patch'
+#
 # End of 10.2 tests
 #

mysql-test/t/func_json.test

@@ -494,6 +494,49 @@ SELECT JSON_ARRAY(_UTF8 'str', JSON_OBJECT(_LATIN1 'plugin', _LATIN1'unix_socket
 SELECT CHARSET(JSON_ARRAY());
 SELECT CHARSET(JSON_OBJECT());
 
+--echo #
+--echo # MDEV-13992 Implement JSON_MERGE_PATCH
+--echo #
+
+CREATE TABLE merge_t(
+id INT PRIMARY KEY AUTO_INCREMENT,
+target VARCHAR(100), patch VARCHAR(100)
+);
+INSERT INTO merge_t(target, patch) VALUES
+('{"a":"b"}', '{"a":"c"}'),
+('{"a":"b"}', '{"b":"c"}'),
+('{"a":"b"}', '{"a":null}'),
+('{"a":"b", "b":"c"}', '{"a":null}'),
+('{"a":["b"]}', '{"a":"c"}'),
+('{"a":"c"}', '{"a":["b"]}'),
+('{"a": {"b":"c"}}', '{"a": {"b":"d", "c":null}}'),
+('{"a":[{"b":"c"}]}', '{"a": [1]}'),
+('["a","b"]', '["c","d"]'),
+('{"a":"b"}', '["c"]'),
+('{"a":"foo"}', 'null'),
+('{"a":"foo"}', '"bar"'),
+('{"e":null}', '{"a":1}'),
+('[1,2]', '{"a":"b", "c":null}'),
+('{}', '{"a":{"bb":{"ccc":null}}}'),
+(NULL, '{}'),
+('{}', NULL);
+SELECT id, target, patch,
+       JSON_MERGE_PATCH(target, patch) AS merged,
+       JSON_EXTRACT(JSON_MERGE_PATCH(target, patch), '$.a') AS a
+FROM merge_t ORDER BY id;
+DROP TABLE merge_t;
+
+SELECT JSON_MERGE_PATCH('{"a":"b"}', NULL, '{"c":"d"}');
+SELECT JSON_MERGE_PATCH(NULL, '[1,2,3]');
+SELECT JSON_MERGE_PATCH('{"a":"b"}', NULL, '[1,2,3]', '{"c":null,"d":"e"}');
+
+--error ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT
+SELECT JSON_MERGE_PATCH();
+--error ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT
+SELECT JSON_MERGE_PATCH('{}');
+SELECT JSON_MERGE_PATCH('{', '[1,2,3]');
+SELECT JSON_MERGE_PATCH('{"a":"b"}', '[1,');
+
 --echo #
 --echo # End of 10.2 tests
 --echo #

sql/item_create.cc

@@ -2049,6 +2049,19 @@ class Create_func_json_merge : public Create_native_func
 };
 
 
+class Create_func_json_merge_patch : public Create_native_func
+{
+public:
+  virtual Item *create_native(THD *thd, LEX_STRING name, List<Item> *item_list);
+
+  static Create_func_json_merge_patch s_singleton;
+
+protected:
+  Create_func_json_merge_patch() {}
+  virtual ~Create_func_json_merge_patch() {}
+};
+
+
 class Create_func_json_quote : public Create_func_arg1
 {
 public:
@@ -5414,6 +5427,30 @@ Create_func_json_merge::create_native(THD *thd, LEX_STRING name,
 }
 
 
+Create_func_json_merge_patch Create_func_json_merge_patch::s_singleton;
+
+Item*
+Create_func_json_merge_patch::create_native(THD *thd, LEX_STRING name,
+                                           List<Item> *item_list)
+{
+  Item *func;
+  int arg_count;
+
+  if (item_list == NULL ||
+      (arg_count= item_list->elements) < 2) // json, json
+  {
+    my_error(ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT, MYF(0), name.str);
+    func= NULL;
+  }
+  else
+  {
+    func= new (thd->mem_root) Item_func_json_merge_patch(thd, *item_list);
+  }
+
+  return func;
+}
+
+
 Create_func_json_contains Create_func_json_contains::s_singleton;
 
 Item*
@@ -6825,6 +6862,8 @@ static Native_func_registry func_array[] =
   { { C_STRING_WITH_LEN("JSON_LENGTH") }, BUILDER(Create_func_json_length)},
   { { C_STRING_WITH_LEN("JSON_LOOSE") }, BUILDER(Create_func_json_loose)},
   { { C_STRING_WITH_LEN("JSON_MERGE") }, BUILDER(Create_func_json_merge)},
+  { { C_STRING_WITH_LEN("JSON_MERGE_PATCH") }, BUILDER(Create_func_json_merge_patch)},
+  { { C_STRING_WITH_LEN("JSON_MERGE_PRESERVE") }, BUILDER(Create_func_json_merge)},
   { { C_STRING_WITH_LEN("JSON_QUERY") }, BUILDER(Create_func_json_query)},
   { { C_STRING_WITH_LEN("JSON_QUOTE") }, BUILDER(Create_func_json_quote)},
   { { C_STRING_WITH_LEN("JSON_OBJECT") }, BUILDER(Create_func_json_object)},

sql/item_jsonfunc.cc

@@ -2150,6 +2150,331 @@ String *Item_func_json_merge::val_str(String *str)
 }
 
 
+static int copy_value_patch(String *str, json_engine_t *je)
+{
+  int first_key= 1;
+
+  if (je->value_type != JSON_VALUE_OBJECT)
+  {
+    const uchar *beg, *end;
+
+    beg= je->value_begin;
+
+    if (!json_value_scalar(je))
+    {
+      if (json_skip_level(je))
+        return 1;
+      end= je->s.c_str;
+    }
+    else
+      end= je->value_end;
+
+    if (append_simple(str, beg, end-beg))
+      return 1;
+
+    return 0;
+  }
+  /* JSON_VALUE_OBJECT */
+
+  if (str->append("{", 1))
+    return 1;
+  while (json_scan_next(je) == 0 && je->state != JST_OBJ_END)
+  {
+    const uchar *key_start;
+    /* Loop through the Json_1 keys and compare with the Json_2 keys. */
+    DBUG_ASSERT(je->state == JST_KEY);
+    key_start= je->s.c_str;
+
+    if (json_read_value(je))
+      return 1;
+
+    if (je->value_type == JSON_VALUE_NULL)
+      continue;
+
+    if (!first_key)
+    {
+      if (str->append(", ", 2))
+        return 3;
+    }
+    else
+      first_key= 0;
+
+    if (str->append("\"", 1) ||
+        append_simple(str, key_start, je->value_begin - key_start) ||
+        copy_value_patch(str, je))
+      return 1;
+  }
+  if (str->append("}", 1))
+    return 1;
+
+  return 0;
+}
+
+
+static int do_merge_patch(String *str, json_engine_t *je1, json_engine_t *je2,
+                          bool *empty_result)
+{
+  if (json_read_value(je1) || json_read_value(je2))
+    return 1;
+
+  if (je1->value_type == JSON_VALUE_OBJECT &&
+      je2->value_type == JSON_VALUE_OBJECT)
+  {
+    json_engine_t sav_je1= *je1;
+    json_engine_t sav_je2= *je2;
+
+    int first_key= 1;
+    json_string_t key_name;
+    size_t sav_len;
+    bool mrg_empty;
+  
+    *empty_result= FALSE;
+    json_string_set_cs(&key_name, je1->s.cs);
+
+    if (str->append("{", 1))
+      return 3;
+    while (json_scan_next(je1) == 0 &&
+           je1->state != JST_OBJ_END)
+    {
+      const uchar *key_start, *key_end;
+      /* Loop through the Json_1 keys and compare with the Json_2 keys. */
+      DBUG_ASSERT(je1->state == JST_KEY);
+      key_start= je1->s.c_str;
+      do
+      {
+        key_end= je1->s.c_str;
+      } while (json_read_keyname_chr(je1) == 0);
+
+      if (je1->s.error)
+        return 1;
+
+      sav_len= str->length();
+
+      if (!first_key)
+      {
+        if (str->append(", ", 2))
+          return 3;
+        *je2= sav_je2;
+      }
+
+      if (str->append("\"", 1) ||
+          append_simple(str, key_start, key_end - key_start) ||
+          str->append("\":", 2))
+        return 3;
+
+      while (json_scan_next(je2) == 0 &&
+          je2->state != JST_OBJ_END)
+      {
+        int ires;
+        DBUG_ASSERT(je2->state == JST_KEY);
+        json_string_set_str(&key_name, key_start, key_end);
+        if (!json_key_matches(je2, &key_name))
+        {
+          if (je2->s.error || json_skip_key(je2))
+            return 2;
+          continue;
+        }
+
+        /* Json_2 has same key as Json_1. Merge them. */
+        if ((ires= do_merge_patch(str, je1, je2, &mrg_empty)))
+          return ires;
+
+        if (mrg_empty)
+          str->length(sav_len);
+        else
+          first_key= 0;
+
+        goto merged_j1;
+      }
+
+      if (je2->s.error)
+        return 2;
+
+      key_start= je1->s.c_str;
+      /* Just append the Json_1 key value. */
+      if (json_skip_key(je1))
+        return 1;
+      if (append_simple(str, key_start, je1->s.c_str - key_start))
+        return 3;
+      first_key= 0;
+
+merged_j1:
+      continue;
+    }
+
+    *je2= sav_je2;
+    /*
+      Now loop through the Json_2 keys.
+      Skip if there is same key in Json_1
+    */
+    while (json_scan_next(je2) == 0 &&
+           je2->state != JST_OBJ_END)
+    {
+      const uchar *key_start, *key_end;
+      DBUG_ASSERT(je2->state == JST_KEY);
+      key_start= je2->s.c_str;
+      do
+      {
+        key_end= je2->s.c_str;
+      } while (json_read_keyname_chr(je2) == 0);
+
+      if (je2->s.error)
+        return 1;
+
+      *je1= sav_je1;
+      while (json_scan_next(je1) == 0 &&
+             je1->state != JST_OBJ_END)
+      {
+        DBUG_ASSERT(je1->state == JST_KEY);
+        json_string_set_str(&key_name, key_start, key_end);
+        if (!json_key_matches(je1, &key_name))
+        {
+          if (je1->s.error || json_skip_key(je1))
+            return 2;
+          continue;
+        }
+        if (json_skip_key(je2) ||
+            json_skip_level(je1))
+          return 1;
+        goto continue_j2;
+      }
+
+      if (je1->s.error)
+        return 2;
+
+
+      sav_len= str->length();
+
+      if (!first_key && str->append(", ", 2))
+        return 3;
+
+      if (str->append("\"", 1) ||
+          append_simple(str, key_start, key_end - key_start) ||
+          str->append("\":", 2))
+        return 3;
+
+      if (json_read_value(je2))
+        return 1;
+
+      if (je2->value_type == JSON_VALUE_NULL)
+        str->length(sav_len);
+      else
+      {
+        if (copy_value_patch(str, je2))
+          return 1;
+        first_key= 0;
+      }
+
+continue_j2:
+      continue;
+    }
+
+    if (str->append("}", 1))
+      return 3;
+  }
+  else
+  {
+    if (!json_value_scalar(je1) && json_skip_level(je1))
+      return 1;
+
+    *empty_result= je2->value_type == JSON_VALUE_NULL;
+    if (!(*empty_result) && copy_value_patch(str, je2))
+      return 1;
+  }
+
+  return 0;
+}
+
+
+String *Item_func_json_merge_patch::val_str(String *str)
+{
+  DBUG_ASSERT(fixed == 1);
+  json_engine_t je1, je2;
+  String *js1= args[0]->val_json(&tmp_js1), *js2=NULL;
+  uint n_arg;
+  bool empty_result, merge_to_null;
+
+  merge_to_null= args[0]->null_value;
+
+  for (n_arg=1; n_arg < arg_count; n_arg++)
+  {
+    js2= args[n_arg]->val_json(&tmp_js2);
+    if (args[n_arg]->null_value)
+    {
+      merge_to_null= true;
+      goto cont_point;
+    }
+
+    json_scan_start(&je2, js2->charset(),(const uchar *) js2->ptr(),
+                    (const uchar *) js2->ptr() + js2->length());
+
+    if (merge_to_null)
+    {
+      if (json_read_value(&je2))
+        goto error_return;
+      if (je2.value_type == JSON_VALUE_OBJECT)
+      {
+        merge_to_null= true;
+        goto cont_point;
+      }
+      merge_to_null= false;
+      str->set(js2->ptr(), js2->length(), js2->charset());
+      goto cont_point;
+    }
+
+    str->set_charset(js1->charset());
+    str->length(0);
+
+
+    json_scan_start(&je1, js1->charset(),(const uchar *) js1->ptr(),
+                    (const uchar *) js1->ptr() + js1->length());
+
+    if (do_merge_patch(str, &je1, &je2, &empty_result))
+      goto error_return;
+
+    if (empty_result)
+      str->append("null");
+
+cont_point:
+    {
+      /* Swap str and js1. */
+      if (str == &tmp_js1)
+      {
+        str= js1;
+        js1= &tmp_js1;
+      }
+      else
+      {
+        js1= str;
+        str= &tmp_js1;
+      }
+    }
+  }
+
+  if (merge_to_null)
+    goto null_return;
+
+  json_scan_start(&je1, js1->charset(),(const uchar *) js1->ptr(),
+                  (const uchar *) js1->ptr() + js1->length());
+  str->length(0);
+  str->set_charset(js1->charset());
+  if (json_nice(&je1, str, Item_func_json_format::LOOSE))
+    goto error_return;
+
+  null_value= 0;
+  return str;
+
+error_return:
+  if (je1.s.error)
+    report_json_error(js1, &je1, 0);
+  if (je2.s.error)
+    report_json_error(js2, &je2, n_arg);
+null_return:
+  null_value= 1;
+  return NULL;
+}
+
+
 bool Item_func_json_length::fix_length_and_dec()
 {
   if (arg_count > 1)

sql/item_jsonfunc.h

@@ -291,12 +291,24 @@ class Item_func_json_merge: public Item_func_json_array
     Item_func_json_array(thd, list) {}
   String *val_str(String *);
   bool is_json_type() { return true; }
-  const char *func_name() const { return "json_merge"; }
+  const char *func_name() const { return "json_merge_preserve"; }
   Item *get_copy(THD *thd, MEM_ROOT *mem_root)
   { return get_item_copy<Item_func_json_merge>(thd, mem_root, this); }
 };
 
 
+class Item_func_json_merge_patch: public Item_func_json_merge
+{
+public:
+  Item_func_json_merge_patch(THD *thd, List<Item> &list):
+    Item_func_json_merge(thd, list) {}
+  const char *func_name() const { return "json_merge_patch"; }
+  String *val_str(String *);
+  Item *get_copy(THD *thd, MEM_ROOT *mem_root)
+  { return get_item_copy<Item_func_json_merge_patch>(thd, mem_root, this); }
+};
+
+
 class Item_func_json_length: public Item_int_func
 {
 protected: