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MDEV-36381: Comment "Procedure of keys generation ..." is in the wrong place

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Move it from the middle of table.cc to sql_select.cc:generate_derived_keys()
This commit is contained in:
Sergei Petrunia
2025-03-25 14:42:58 +02:00
parent 33a462e0b1
commit 47d11328c9
2 changed files with 30 additions and 31 deletions
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30
sql/sql_select.cc
View File

@@ -14059,6 +14059,36 @@ bool generate_derived_keys_for_table(KEYUSE *keyuse, uint count, uint keys)
} }
/*
Procedure of keys generation for result tables of materialized derived
tables/views.
A key is generated for each equi-join pair {derived_table, some_other_table}.
Each generated key consists of fields of derived table used in equi-join.
Example:
SELECT * FROM (SELECT * FROM t1 GROUP BY 1) tt JOIN
t1 ON tt.f1=t1.f3 and tt.f2.=t1.f4;
In this case for the derived table tt one key will be generated. It will
consist of two parts f1 and f2.
Example:
SELECT * FROM (SELECT * FROM t1 GROUP BY 1) tt JOIN
t1 ON tt.f1=t1.f3 JOIN
t2 ON tt.f2=t2.f4;
In this case for the derived table tt two keys will be generated.
One key over f1 field, and another key over f2 field.
Currently optimizer may choose to use only one such key, thus the second
one will be dropped after range optimizer is finished.
See also JOIN::drop_unused_derived_keys function.
Example:
SELECT * FROM (SELECT * FROM t1 GROUP BY 1) tt JOIN
t1 ON tt.f1=a_function(t1.f3);
In this case for the derived table tt one key will be generated. It will
consist of one field - f1.
*/
static static
bool generate_derived_keys(DYNAMIC_ARRAY *keyuse_array) bool generate_derived_keys(DYNAMIC_ARRAY *keyuse_array)
{ {

31
sql/table.cc
View File

@@ -9956,37 +9956,6 @@ int TABLE_LIST::fetch_number_of_rows()
return error; return error;
} }
/*
Procedure of keys generation for result tables of materialized derived
tables/views.
A key is generated for each equi-join pair derived table-another table.
Each generated key consists of fields of derived table used in equi-join.
Example:
SELECT * FROM (SELECT * FROM t1 GROUP BY 1) tt JOIN
t1 ON tt.f1=t1.f3 and tt.f2.=t1.f4;
In this case for the derived table tt one key will be generated. It will
consist of two parts f1 and f2.
Example:
SELECT * FROM (SELECT * FROM t1 GROUP BY 1) tt JOIN
t1 ON tt.f1=t1.f3 JOIN
t2 ON tt.f2=t2.f4;
In this case for the derived table tt two keys will be generated.
One key over f1 field, and another key over f2 field.
Currently optimizer may choose to use only one such key, thus the second
one will be dropped after range optimizer is finished.
See also JOIN::drop_unused_derived_keys function.
Example:
SELECT * FROM (SELECT * FROM t1 GROUP BY 1) tt JOIN
t1 ON tt.f1=a_function(t1.f3);
In this case for the derived table tt one key will be generated. It will
consist of one field - f1.
*/
/* /*
@brief @brief