MDEV-34705: Binlog in Engine: Start of binlog reader (untested, incomplete)

Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>

mysql-test/suite/binlog/t/binlog_in_engine.test

@@ -18,7 +18,7 @@ SET SESSION binlog_format= ROW;
 --echo *** Do $num_trx transactions ...
 --disable_query_log
 --let $i= 0
-while ($i < 1500) {
+while ($i < $num_trx) {
   eval INSERT INTO t2 VALUES ($i, REPEAT("x", 2048));
   inc $i;
 }

sql/handler.h

@@ -59,6 +59,7 @@ class Field_varstring;
 class Field_blob;
 class Column_definition;
 class select_result;
+class handler_binlog_reader;
 
 // the following is for checking tables
 
@@ -1528,6 +1529,10 @@ struct handlerton
   void (*update_optimizer_costs)(OPTIMIZER_COSTS *costs);
   void *optimizer_costs;                        /* Costs are stored here */
 
+  /* Optional implementation of binlog in the engine. */
+  handler_binlog_reader * (*get_binlog_reader)();
+  int (*binlog_data)(uchar *data, size_t len);
+
    /*
      Optional clauses in the CREATE/ALTER TABLE
    */
@@ -5791,4 +5796,45 @@ inline void Cost_estimate::reset(handler *file)
   avg_io_cost= file->DISK_READ_COST * file->DISK_READ_RATIO;
 }
 
+
+/*
+  Class for reading a binlog implemented in an engine.
+*/
+class handler_binlog_reader {
+public:
+  /* ToDo: Should some of this state go to the derived class, in case different engines might want to do something different? */
+
+  /* The file number of the currently-being-read binlog file. */
+  uint64_t cur_file_no;
+  /* The current offset into the binlog file. */
+  uint64_t cur_file_offset;
+  /*
+    Open file handle of binlog file.
+    This may be NULL if the currently-being-read binlog file is "hot" and
+    is being read from in-memory buffers while the data may not yet be
+    written out to the file on the OS level.
+  */
+  File cur_file;
+  /* Position and length of any remaining data in buf[]. */
+  uint32_t buf_data_pos;
+  uint32_t buf_data_remain;
+  /* Buffer used when reading data out via read_binlog_data(). */
+  uchar buf[32768];
+
+  handler_binlog_reader()
+    : cur_file_no(~(uint64_t)0), cur_file_offset(0), cur_file(0),
+      buf_data_pos(0), buf_data_remain(0)
+  { }
+  virtual int read_binlog_data(uchar *buf, uint32_t len) = 0;
+
+/*
+  cur_file_no      -> implicitly gives file/tablespace
+  cur_file_offset  -> implicitly gives page
+  cur_file_fh      -> open fh, if any
+  cur_chunk_len
+  cur_chunk_sofar
+*/
+  virtual ~handler_binlog_reader() { };
+};
+
 #endif /* HANDLER_INCLUDED */

storage/innobase/handler/ha_innodb.cc

@@ -4092,6 +4092,7 @@ static int innodb_init(void* p)
 		= innodb_prepare_commit_versioned;
 
         innobase_hton->update_optimizer_costs= innobase_update_optimizer_costs;
+        innobase_hton->get_binlog_reader= innodb_get_binlog_reader;
 
 	innodb_remember_check_sysvar_funcs();
 

storage/innobase/include/fsp0fsp.h

@@ -581,6 +581,8 @@ void fsp_shrink_temp_space();
 
 extern void fsp_binlog_test(const uchar *data, uint32_t len);
 extern void fsp_binlog_trx(trx_t *trx, mtr_t *mtr);
+class handler_binlog_reader;
+extern handler_binlog_reader *innodb_get_binlog_reader();
 
 #ifndef UNIV_DEBUG
 # define fsp_init_file_page(space, block, mtr) fsp_init_file_page(block, mtr)