Fixed for Ia64 + delayed key creation + a lot of small bug fixes

1 files changed, 22 insertions, 0 deletions

diff --git a/Docs/internals.texi b/Docs/internals.texi
index 01f5b0a346c..06a9c1d9265 100644
--- a/Docs/internals.texi
+++ b/Docs/internals.texi
@@ -121,6 +121,28 @@ After this it will give other threads a possibility to open the
 same tables.
 @end itemize
 
+@node Filesort
+@chapter How do MySQL do 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.
+- Repeate the above until all rows has 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.
+- 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.
+  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) .
+
 @node Index
 @unnumbered Index