maria-developers team mailing list archive

[Mohammed Hammaad Mateen <myfriendhammad@xxxxxxxxx>]

Greetings,
Hope you are safe and doing great,

This post describes the things I've done in my third week [ 18-24 May ] of
Community Bonding Period under the mentor-ship of Sergei Golubchik and
Oleksandr Byelkin for GSoC-20. The tasks taken up for this week was to
study and analyze:

*INSERT.... RETURNING:*
• *TableList* consists of 1 table instance to use, where each instance is a
structure consisting of db argument, table name argument, alias argument
and lock type argument. *Referenced this from the table.h file.*
• In *sql_parse.cc* <http://sql_parse.cc> under *case SQLCOM_INSERT*:
   we do a DBUG_ASSERT where first_table == all_table && first_table!=0 //
we check if only 1 table is used and the table used is already created.
• if lex-> has_returning() we increment the system status var by 1 and
perform analyze.. insert.. returning.
• we compute result by mysql_insert function by passing the following
arguments.
- Thread Handler thd
- all table instances
- list of all the fields used
- the values we want to insert
- the list of update feilds
- and update value list
- duplicate flag
- ignore
- result of select
• if Inserting fails due to some reason we equate result to
send_explain(thd)
• we also update the MYSQL_INSERT_DONE with result of insert and the the
row count.

*INSERT.. SELECT.. RETURNING:*
• We fix the lock on first table.
• lock other tables until command is written to the binary log.
• the procedure is same as discussed earlier with respect to insert....
returning.
• To switch to the second table we traverse from first_table to (->)
next_local and we compute select result with the help of select insert
function.
• we can now unlock the tables and we also need to check if something
changed after unlocking, of that happens we should invalidate the table
from the query cache using query_cache_invalidate3 function.
• Manual cleaning of select result obtained from select insert must be done.

Regards,
Mohammed Hammaad Mateen