[MDEV-6877] Added binlog_row_image system variable

The system variable is present but it does not do anything yet.

sql/sql_class.h

@@ -96,6 +96,16 @@ enum enum_mark_columns
 { MARK_COLUMNS_NONE, MARK_COLUMNS_READ, MARK_COLUMNS_WRITE};
 enum enum_filetype { FILETYPE_CSV, FILETYPE_XML };
 
+enum enum_binlog_row_image {
+  /** PKE in the before image and changed columns in the after image */
+  BINLOG_ROW_IMAGE_MINIMAL= 0,
+  /** Whenever possible, before and after image contain all columns except blobs. */
+  BINLOG_ROW_IMAGE_NOBLOB= 1,
+  /** All columns in both before and after image. */
+  BINLOG_ROW_IMAGE_FULL= 2
+};
+
+
 /* Bits for different SQL modes modes (including ANSI mode) */
 #define MODE_REAL_AS_FLOAT              (1ULL << 0)
 #define MODE_PIPES_AS_CONCAT            (1ULL << 1)
@@ -588,6 +598,7 @@ typedef struct system_variables
   /* Flags for slow log filtering */
   ulong log_slow_rate_limit; 
   ulong binlog_format; ///< binlog format for this thd (see enum_binlog_format)
+  ulong binlog_row_image;
   ulong progress_report_time;
   ulong completion_type;
   ulong query_cache_type;

sql/sys_vars.cc

@@ -5200,6 +5200,22 @@ static Sys_var_mybool Sys_encrypt_tmp_files(
        READ_ONLY GLOBAL_VAR(encrypt_tmp_files),
        CMD_LINE(OPT_ARG), DEFAULT(TRUE));
 
+static const char *binlog_row_image_names[]= {"MINIMAL", "NOBLOB", "FULL", NullS};
+static Sys_var_enum Sys_binlog_row_image(
+       "binlog_row_image",
+       "Controls whether rows should be logged in 'FULL', 'NOBLOB' or "
+       "'MINIMAL' formats. 'FULL', means that all columns in the before "
+       "and after image are logged. 'NOBLOB', means that mysqld avoids logging "
+       "blob columns whenever possible (eg, blob column was not changed or "
+       "is not part of primary key). 'MINIMAL', means that a PK equivalent (PK "
+       "columns or full row if there is no PK in the table) is logged in the "
+       "before image, and only changed columns are logged in the after image. "
+       "(Default: FULL).",
+       SESSION_VAR(binlog_row_image), CMD_LINE(REQUIRED_ARG),
+       binlog_row_image_names, DEFAULT(BINLOG_ROW_IMAGE_FULL),
+       NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(NULL),
+       ON_UPDATE(NULL));
+
 static bool check_pseudo_slave_mode(sys_var *self, THD *thd, set_var *var)
 {
   longlong previous_val= thd->variables.pseudo_slave_mode;