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MDEV-6111 Optimizer Trace

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This task involves the implementation for the optimizer trace.

This feature produces a trace for any SELECT/UPDATE/DELETE/,
which contains information about decisions taken by the optimizer during
the optimization phase (choice of table access method, various costs,
transformations, etc). This feature would help to tell why some decisions were
taken by the optimizer and why some were rejected.

Trace is session-local, controlled by the @@optimizer_trace variable.
To enable optimizer trace we need to write:
   set @@optimizer_trace variable= 'enabled=on';

To display the trace one can run:
   SELECT trace FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE;

This task also involves:
    MDEV-18489: Limit the memory used by the optimizer trace
    introduces a switch optimizer_trace_max_mem_size which limits
    the memory used by the optimizer trace. This was implemented by
    Sergei Petrunia.
This commit is contained in:
Varun Gupta
2019-02-13 11:22:16 +05:30
parent 6b979416e0
commit be8709eb7b
47 changed files with 8227 additions and 622 deletions
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8
sql/sql_parse.cc
View File

@ -100,6 +100,7 @@
#include "set_var.h"
#include "sql_bootstrap.h"
#include "sql_sequence.h"
#include "opt_trace.h"
#include "my_json_writer.h"
@ -3412,6 +3413,13 @@ mysql_execute_command(THD *thd)
#ifdef HAVE_REPLICATION
} /* endif unlikely slave */
#endif
Opt_trace_start ots(thd, all_tables, lex->sql_command, &lex->var_list,
thd->query(), thd->query_length(),
thd->variables.character_set_client);
Json_writer_object trace_command(thd);
Json_writer_array trace_command_steps(thd, "steps");
#ifdef WITH_WSREP
if (WSREP(thd))
{