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nexedi
MariaDB
Commits
1777d4db
Commit
1777d4db
authored
Aug 15, 2000
by
sasha@mysql.sashanet.com
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Merge work:/home/bk/mysql
into mysql.sashanet.com:/home/sasha/src/bk/mysql
parents
ac9de478
c442a5dd
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Docs/internals.texi
Docs/internals.texi
+11
-13
Docs/manual.texi
Docs/manual.texi
+41
-42
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Docs/internals.texi
View file @
1777d4db
...
...
@@ -7,7 +7,7 @@
@c @synindex tp fn cp
@synindex cp fn
@iftex
@c Well this is normal in Europe. Maybe this shold go into the include.texi?
@c Well this is normal in Europe. Maybe this sho
u
ld go into the include.texi?
@afourpaper
@end iftex
@c Get version and other info
...
...
@@ -47,10 +47,10 @@ This is a manual about @strong{MySQL} internals.
@end menu
@node caching
@chapter How
do MySQL handle
caching
@chapter How
MySQL handles
caching
MySQL has the following caches:
(Note that the some of the filename ha
s wrong spelling of cache
:)
(Note that the some of the filename ha
ve a wrong spelling of cache.
:)
@itemize @bullet
@item Key cache
...
...
@@ -76,17 +76,17 @@ cached for each user/database combination. sql/sql_acl.cc
@item Heap table cache
Many use of GROUP BY or DISTINCT caches all found
rows in a HEAP table (this is a very quick
, in
memory table with hash index)
rows in a HEAP table (this is a very quick
in-
memory table with hash index)
@item Join row cache.
For every full join in a SELECT statement (a full join here means there
w
as
no keys that one could use to find the next table in a list), the
w
ere
no keys that one could use to find the next table in a list), the
found rows are cached in a join cache. One SELECT query can use many
join caches in the worst case.
@end itemize
@node flush tables
@chapter How
do MySQL handle
flush tables
@chapter How
MySQL handles
flush tables
@itemize @bullet
@item
...
...
@@ -122,23 +122,23 @@ same tables.
@end itemize
@node Filesort
@chapter How
do MySQL do
sorting (filesort)
@chapter How
MySQL does
sorting (filesort)
- Read all rows according to key or by table-scanning.
- Store the sort-key in a buffer (sort
_
buffer).
- When the buffer gets full, run a qsort on it and store the result
in a temporary file. Save a pointer to the sorted block.
- Repeat
e the above until all rows has
been read.
- Repeat
the above until all rows have
been read.
- Repeat the following until there is less than MERGEBUFF2 (15) blocks left.
- Do a multi-merge of up to MERGEBUFF (7) regions to one block in
another temporary file. Repeat until all blocks from the first file
is
in the second file.
are
in the second file.
- On the last multi-merge, only the pointer to the row (last part of
the sort-key) is written to a result file.
- Now the code in sql/records.cc will be used to read through the
in sorted order by using the row pointersin the result file.
- Now the code in sql/records.cc will be used to read through the
m
in sorted order by using the row pointers
in the result file.
To optimize this, we read in a big block of row pointers, sort these
and then we read the rows in the sorted order into a row buffer
(record
_
buffer) .
...
...
@@ -152,5 +152,3 @@ same tables.
@contents
@bye
Do text here do something ??
Docs/manual.texi
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1777d4db
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