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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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28
mysql-test/suite/sys_vars/r/sysvars_server_embedded.result
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@ -2742,6 +2742,34 @@ NUMERIC_BLOCK_SIZE NULL
ENUM_VALUE_LIST index_merge,index_merge_union,index_merge_sort_union,index_merge_intersection,index_merge_sort_intersection,engine_condition_pushdown,index_condition_pushdown,derived_merge,derived_with_keys,firstmatch,loosescan,materialization,in_to_exists,semijoin,partial_match_rowid_merge,partial_match_table_scan,subquery_cache,mrr,mrr_cost_based,mrr_sort_keys,outer_join_with_cache,semijoin_with_cache,join_cache_incremental,join_cache_hashed,join_cache_bka,optimize_join_buffer_size,table_elimination,extended_keys,exists_to_in,orderby_uses_equalities,condition_pushdown_for_derived,split_materialized,condition_pushdown_for_subquery,default
READ_ONLY NO
COMMAND_LINE_ARGUMENT REQUIRED
VARIABLE_NAME OPTIMIZER_TRACE
SESSION_VALUE enabled=off
GLOBAL_VALUE enabled=off
GLOBAL_VALUE_ORIGIN COMPILE-TIME
DEFAULT_VALUE enabled=off
VARIABLE_SCOPE SESSION
VARIABLE_TYPE FLAGSET
VARIABLE_COMMENT Controls tracing of the Optimizer: optimizer_trace=option=val[,option=val...], where option is one of {enabled} and val is one of {on, off, default}
NUMERIC_MIN_VALUE NULL
NUMERIC_MAX_VALUE NULL
NUMERIC_BLOCK_SIZE NULL
ENUM_VALUE_LIST enabled,default
READ_ONLY NO
COMMAND_LINE_ARGUMENT REQUIRED
VARIABLE_NAME OPTIMIZER_TRACE_MAX_MEM_SIZE
SESSION_VALUE 1048576
GLOBAL_VALUE 1048576
GLOBAL_VALUE_ORIGIN COMPILE-TIME
DEFAULT_VALUE 1048576
VARIABLE_SCOPE SESSION
VARIABLE_TYPE BIGINT UNSIGNED
VARIABLE_COMMENT Maximum allowed size of an optimizer trace
NUMERIC_MIN_VALUE 0
NUMERIC_MAX_VALUE 18446744073709551615
NUMERIC_BLOCK_SIZE 1
ENUM_VALUE_LIST NULL
READ_ONLY NO
COMMAND_LINE_ARGUMENT REQUIRED
VARIABLE_NAME OPTIMIZER_USE_CONDITION_SELECTIVITY
SESSION_VALUE 4
GLOBAL_VALUE 4