MDEV-19317 TEXT column accepts too long literals as a default value

Adding new virtual methods in Field:
- make_empty_rec_store_default_value()
- make_empty_rec_reset()

This simplifies the logic for every Field type,
and makes the code more friendly to pluggable data types.

mysql-test/main/type_blob.result

@@ -1093,3 +1093,34 @@ drop table t1;
 #
 # End of 10.2 test
 #
+#
+# Start of 10.4 test
+#
+#
+# MDEV-19317 TEXT column accepts too long literals as a default value
+#
+EXECUTE IMMEDIATE 'CREATE OR REPLACE TABLE t1 (a TINYTEXT DEFAULT ?)' USING REPEAT('a', 255);
+INSERT INTO t1 VALUES ();
+SELECT LENGTH(a), LENGTH(DEFAULT(a)) FROM t1;
+LENGTH(a)	LENGTH(DEFAULT(a))
+255	255
+DROP TABLE t1;
+EXECUTE IMMEDIATE 'CREATE OR REPLACE TABLE t1 (a TINYTEXT DEFAULT ?)' USING REPEAT('a', 256);
+ERROR 42000: Invalid default value for 'a'
+CREATE OR REPLACE TABLE t1 (a TINYTEXT DEFAULT 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');
+ERROR 42000: Invalid default value for 'a'
+EXECUTE IMMEDIATE 'CREATE OR REPLACE TABLE t1 (a TEXT DEFAULT ?)' USING REPEAT('a', 256);
+INSERT INTO t1 VALUES ();
+SELECT LENGTH(a), LENGTH(DEFAULT(a)) FROM t1;
+LENGTH(a)	LENGTH(DEFAULT(a))
+256	256
+DROP TABLE t1;
+CREATE OR REPLACE TABLE t1 (a TEXT DEFAULT 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');
+INSERT INTO t1 VALUES ();
+SELECT LENGTH(a), LENGTH(DEFAULT(a)) FROM t1;
+LENGTH(a)	LENGTH(DEFAULT(a))
+256	256
+DROP TABLE t1;
+#
+# End of 10.4 test
+#

mysql-test/main/type_blob.test

@@ -702,3 +702,39 @@ drop table t1;
 --echo #
 --echo # End of 10.2 test
 --echo #
+
+
+--echo #
+--echo # Start of 10.4 test
+--echo #
+
+--echo #
+--echo # MDEV-19317 TEXT column accepts too long literals as a default value
+--echo #
+
+EXECUTE IMMEDIATE 'CREATE OR REPLACE TABLE t1 (a TINYTEXT DEFAULT ?)' USING REPEAT('a', 255);
+INSERT INTO t1 VALUES ();
+SELECT LENGTH(a), LENGTH(DEFAULT(a)) FROM t1;
+DROP TABLE t1;
+
+--error ER_INVALID_DEFAULT
+EXECUTE IMMEDIATE 'CREATE OR REPLACE TABLE t1 (a TINYTEXT DEFAULT ?)' USING REPEAT('a', 256);
+
+--error ER_INVALID_DEFAULT
+CREATE OR REPLACE TABLE t1 (a TINYTEXT DEFAULT 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');
+
+
+EXECUTE IMMEDIATE 'CREATE OR REPLACE TABLE t1 (a TEXT DEFAULT ?)' USING REPEAT('a', 256);
+INSERT INTO t1 VALUES ();
+SELECT LENGTH(a), LENGTH(DEFAULT(a)) FROM t1;
+DROP TABLE t1;
+
+CREATE OR REPLACE TABLE t1 (a TEXT DEFAULT 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');
+INSERT INTO t1 VALUES ();
+SELECT LENGTH(a), LENGTH(DEFAULT(a)) FROM t1;
+DROP TABLE t1;
+
+
+--echo #
+--echo # End of 10.4 test
+--echo #

sql/field.cc

@@ -1382,6 +1382,14 @@ error:
 }
 
 
+bool Field::make_empty_rec_store_default_value(THD *thd, Item *item)
+{
+  DBUG_ASSERT(!(flags & BLOB_FLAG));
+  int res= item->save_in_field(this, true);
+  return res != 0 && res != 3;
+}
+
+
 /**
   Numeric fields base class constructor.
 */
@@ -8773,6 +8781,18 @@ void Field_blob::make_send_field(Send_field *field)
 }
 
 
+bool Field_blob::make_empty_rec_store_default_value(THD *thd, Item *item)
+{
+  DBUG_ASSERT(flags & BLOB_FLAG);
+  int res= item->save_in_field(this, true);
+  DBUG_ASSERT(res != 3); // Field_blob never returns 3
+  if (res)
+    return true; // E.g. truncation happened
+  reset(); // Clear the pointer to a String, it should not be written to frm
+  return false;
+}
+
+
 int Field_blob_compressed::store(const char *from, size_t length,
                                  CHARSET_INFO *cs)
 {

sql/field.h

@@ -782,6 +782,11 @@ public:
     @retval false - conversion is needed
   */
   virtual bool memcpy_field_possible(const Field *from) const= 0;
+  virtual bool make_empty_rec_store_default_value(THD *thd, Item *item);
+  virtual void make_empty_rec_reset(THD *thd)
+  {
+    reset();
+  }
   virtual int  store(const char *to, size_t length,CHARSET_INFO *cs)=0;
   virtual int  store_hex_hybrid(const char *str, size_t length);
   virtual int  store(double nr)=0;
@@ -3895,6 +3900,7 @@ public:
            !compression_method() == !from->compression_method() &&
            !table->copy_blobs;
   }
+  bool make_empty_rec_store_default_value(THD *thd, Item *item);
   int store(const char *to, size_t length, CHARSET_INFO *charset);
   using Field_str::store;
   double val_real(void);
@@ -4212,6 +4218,16 @@ public:
     return save_in_field_str(to);
   }
   bool memcpy_field_possible(const Field *from) const { return false; }
+  void make_empty_rec_reset(THD *thd)
+  {
+    if (flags & NOT_NULL_FLAG)
+    {
+      set_notnull();
+      store((longlong) 1, true);
+    }
+    else
+      reset();
+  }
   int  store(const char *to,size_t length,CHARSET_INFO *charset);
   int  store(double nr);
   int  store(longlong nr, bool unsigned_val);
@@ -4278,6 +4294,11 @@ public:
     {
       flags=(flags & ~ENUM_FLAG) | SET_FLAG;
     }
+  void make_empty_rec_reset(THD *thd)
+  {
+    Field::make_empty_rec_reset(thd);
+  }
+
   int  store_field(Field *from) { return from->save_in_field(this); }
   int  store(const char *to,size_t length,CHARSET_INFO *charset);
   int  store(double nr) { return Field_set::store((longlong) nr, FALSE); }

sql/unireg.cc

@@ -974,13 +974,36 @@ static bool pack_fields(uchar **buff_arg, List<Create_field> &create_fields,
   DBUG_RETURN(0);
 }
 
+
+static bool make_empty_rec_store_default(THD *thd, Field *regfield,
+                                         Virtual_column_info *default_value)
+{
+  if (default_value && !default_value->flags)
+  {
+    Item *expr= default_value->expr;
+    // may be already fixed if ALTER TABLE
+    if (expr->fix_fields_if_needed(thd, &expr))
+      return true;
+    DBUG_ASSERT(expr == default_value->expr); // Should not change
+    if (regfield->make_empty_rec_store_default_value(thd, expr))
+    {
+      my_error(ER_INVALID_DEFAULT, MYF(0), regfield->field_name.str);
+      return true;
+    }
+    return false;
+  }
+  regfield->make_empty_rec_reset(thd);
+  return false;
+}
+
+
 /* save an empty record on start of formfile */
 
 static bool make_empty_rec(THD *thd, uchar *buff, uint table_options,
 			   List<Create_field> &create_fields,
 			   uint reclength, ulong data_offset)
 {
-  int error= 0;
+  int error= false;
   uint null_count;
   uchar *null_pos;
   TABLE table;
@@ -1020,7 +1043,7 @@ static bool make_empty_rec(THD *thd, uchar *buff, uint table_options,
                                     field->flags);
     if (!regfield)
     {
-      error= 1;
+      error= true;
       goto err;                                 // End of memory
     }
 
@@ -1037,37 +1060,11 @@ static bool make_empty_rec(THD *thd, uchar *buff, uint table_options,
         !f_bit_as_char(field->pack_flag))
       null_count+= field->length & 7;
 
-    if (field->default_value && !field->default_value->flags &&
+    error= make_empty_rec_store_default(thd, regfield, field->default_value);
-        (!(field->flags & BLOB_FLAG) ||
+    delete regfield; // Avoid memory leaks
-         field->real_field_type() == MYSQL_TYPE_GEOMETRY))
+    if (error)
-    {
-      Item *expr= field->default_value->expr;
-      // may be already fixed if ALTER TABLE
-      int res= expr->fix_fields_if_needed(thd, &expr);
-      if (!res)
-        res= expr->save_in_field(regfield, 1);
-      if (!res && (field->flags & BLOB_FLAG))
-        regfield->reset();
-
-      /* If not ok or warning of level 'note' */
-      if (res != 0 && res != 3)
-      {
-        my_error(ER_INVALID_DEFAULT, MYF(0), regfield->field_name.str);
-        error= 1;
-        delete regfield; //To avoid memory leak
       goto err;
   }
-      delete regfield; //To avoid memory leak
-    }
-    else if (regfield->real_type() == MYSQL_TYPE_ENUM &&
-	     (field->flags & NOT_NULL_FLAG))
-    {
-      regfield->set_notnull();
-      regfield->store((longlong) 1, TRUE);
-    }
-    else
-      regfield->reset();
-  }
   DBUG_ASSERT(data_offset == ((null_count + 7) / 8));
 
   /*