MDEV-10963 Fragmented BINLOG query

The problem was originally stated in
  http://bugs.mysql.com/bug.php?id=82212
The size of an base64-encoded Rows_log_event exceeds its
vanilla byte representation in 4/3 times.
When a binlogged event size is about 1GB mysqlbinlog generates
a BINLOG query that can't be send out due to its size.

It is fixed with fragmenting the BINLOG argument C-string into
(approximate) halves when the base64 encoded event is over 1GB size.
The mysqlbinlog in such case puts out

    SET @binlog_fragment_0='base64-encoded-fragment_0';
    SET @binlog_fragment_1='base64-encoded-fragment_1';
    BINLOG @binlog_fragment_0, @binlog_fragment_1;

to represent a big BINLOG.
For prompt memory release BINLOG handler is made to reset the BINLOG argument
user variables in the middle of processing, as if @binlog_fragment_{0,1} = NULL
is assigned.

Notice the 2 fragments are enough, though the client and server still may
need to tweak their @@max_allowed_packet to satisfy to the fragment
size (which they would have to do anyway with greater number of
fragments, should that be desired).

On the lower level the following changes are made:

Log_event::print_base64()
  remains to call encoder and store the encoded data into a cache but
  now *without* doing any formatting. The latter is left for time
  when the cache is copied to an output file (e.g mysqlbinlog output).
  No formatting behavior is also reflected by the change in the meaning
  of the last argument which specifies whether to cache the encoded data.

Rows_log_event::print_helper()
  is made to invoke a specialized fragmented cache-to-file copying function
  which is

copy_cache_to_file_wrapped()
  that takes care of fragmenting also optionally wraps encoded
  strings (fragments) into SQL stanzas.

my_b_copy_to_file()
  is refactored to into my_b_copy_all_to_file(). The former function
  is generalized
  to accepts more a limit argument to constraint the copying and does
  not reinitialize anymore the cache into reading mode.
  The limit does not do any effect on the fully read cache.

1 files changed, 19 insertions, 2 deletions

diff --git a/client/mysqlbinlog.cc b/client/mysqlbinlog.cc
index bc13aa6c2cc..2c05bb806a9 100644
--- a/client/mysqlbinlog.cc
+++ b/client/mysqlbinlog.cc
@@ -72,6 +72,7 @@ ulong mysqld_net_retry_count = 10L;
 ulong open_files_limit;
 ulong opt_binlog_rows_event_max_size;
 ulonglong test_flags = 0;
+ulong opt_binlog_rows_event_max_encoded_size= MAX_MAX_ALLOWED_PACKET;
 static uint opt_protocol= 0;
 static FILE *result_file;
 static char *result_file_name= 0;
@@ -813,7 +814,12 @@ write_event_header_and_base64(Log_event *ev, FILE *result_file,
 
   /* Write header and base64 output to cache */
   ev->print_header(head, print_event_info, FALSE);
-  ev->print_base64(body, print_event_info, FALSE);
+
+  DBUG_ASSERT(print_event_info->base64_output_mode == BASE64_OUTPUT_ALWAYS);
+
+  ev->print_base64(body, print_event_info,
+                   print_event_info->base64_output_mode !=
+                   BASE64_OUTPUT_DECODE_ROWS);
 
   /* Read data from cache and write to result file */
   if (copy_event_cache_to_file_and_reinit(head, result_file) ||
@@ -852,7 +858,9 @@ static bool print_base64(PRINT_EVENT_INFO *print_event_info, Log_event *ev)
     return 1;
   }
   ev->print(result_file, print_event_info);
-  return print_event_info->head_cache.error == -1;
+  return
+    print_event_info->head_cache.error == -1 ||
+    print_event_info->body_cache.error == -1;
 }
 
 
@@ -1472,6 +1480,15 @@ that may lead to an endless loop.",
    "This value must be a multiple of 256.",
    &opt_binlog_rows_event_max_size, &opt_binlog_rows_event_max_size, 0,
    GET_ULONG, REQUIRED_ARG, UINT_MAX,  256, ULONG_MAX,  0, 256,  0},
+#ifndef DBUG_OFF
+  {"debug-binlog-row-event-max-encoded-size", 0,
+   "The maximum size of base64-encoded rows-event in one BINLOG pseudo-query "
+   "instance. When the computed actual size exceeds the limit "
+   "the BINLOG's argument string is fragmented in two.",
+   &opt_binlog_rows_event_max_encoded_size,
+   &opt_binlog_rows_event_max_encoded_size, 0,
+   GET_ULONG, REQUIRED_ARG, UINT_MAX/4,  256, ULONG_MAX,  0, 256,  0},
+#endif
   {"verify-binlog-checksum", 'c', "Verify checksum binlog events.",
    (uchar**) &opt_verify_binlog_checksum, (uchar**) &opt_verify_binlog_checksum,
    0, GET_BOOL, NO_ARG, 0, 0, 0, 0, 0, 0},