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Dear Sergei Golubchik,

Hope this mail finds you well.

I am Kesha Shah, a third year undergraduate from DA-IICT, Gandhinagar,
India. I was a Google Summer of Code student previous year as well as
Google Code-In mentor with BRL-CAD open source solid modeling
software. The activities related to my contributions at BRL-CAD at
logged by me at -
http://brlcad.org/wiki/User:KeshaSShah/GSoC13/Reports. My other
projects can be found at -
I have good programming hands on C and C++ and would like to take up
and contribute at the Mariadb task of 'CREATE OR REPLACE, CREATE IF
NOT EXISTS, and DROP IF EXISTS' [MDEV-5359] as part of GSOC 2014. I
have studied database systems and compiler construction during my
academics. Your project would help to apply my knowledge by working at
deeper level of coding database internals, thereby contributing to
open source software.

I had checked out the mariadb master branch from bazaar and started
looking into the source code. I found the task more related to update
of the existing mariadb SQL parser. The parser seems to be implemented
as ascendant parser using bison parser generator (GNU version of
YACC). From the current findings I could see the YACC grammar file
sql_yacc.yy under maria/sql/ where I can see the rules defined for
Alternatively I can see the *_SYM lexical tokens defined under the
/maria/sql/lex.h file. Similarly for DROP TABLESPACE_SYM, DROP
TRIGGER_SYM etc could be found. So when sql text input stream is
encountered from SQL interface, it is read and categorized into
lexical tokens by the lexer /maria/sql/sql_lex.cc in the lexical
analysis step. I tried to figure out that we will have to define
additional token 'IF' in the lex.h and 'NOT' and 'EXISTS' are already
defined. I am also looking at the existing user defined actions that
builds the AST nodes (sp_head being the root node for most types) when
relevant grammar rule is satisfied in case of DDL statements. After
semantic analysis (create of stored procs/functions), the next step
would be to amend/define actions for the newly introduced grammar of
handling check of existence of db artefact at the time of DDL
execution. Also at this step the compiler will have to query the
relevant storage engine on DB level or repository level to check if
the DB object exists. This would require me to spend more time on
understanding design pattern followed for the implementation of
classes and behaviours of each of the underlying db artefacts.

It would be interesting for me to know if the steps proposed by me
above are in the right direction or not ?  Also I am aware that I am
late in discussing my proposal with you. But I can assure that I will
be able to deliver the requirements in timely manner under your
guidance. I have formulated initial draft of my proposal and would
like to submit it at the earliest.

Looking forward to you reply. Have a nice day!

Thanks and Regards,
Kesha Shah

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