If the internal ID is stored in the buffer when it is moving inside the
readwritesplit router, the RWBackend can manage the execution of all
commands with a statement ID by replacing the stored ID with the correct
value.
When a COM_STMT_EXECUTE or a COM_STMT_SEND_LONG_DATA command is executed,
the query type of the prepared statement is used. This allows read-only
prepared statements to be load balanced across slaves.
Mapping the handles returned to the client to a session command ID allows
the mapping of client handle to the backend specific handle. Currently,
the mapping is used for diagnostic output only.
The class manages both text and binary protocol prepared statement ID to
type mapping. The text protocol statements are mapped by their plaintext
name and the binary protocol statements are mapped by the session command
ID of the prepared statement.
By mapping the binary protocol prepared statement type to the session
command identifier, we can store the types for both styles of prepared
statements in a very similar manner. When the prepared statement handle is
received from the backend and is sent to the client, the client handle to
session command ID mapping can be done. This allows the mapping of both
client and backend PS handles to internal session command IDs.
The readwritesplit Backend implementation maps the returned PS handles to
session command identifiers. This allows the handles to be retrieven later
on when the prepared statements are executed.
The mxs_mysql_extract_ps_response function extracts the binary protocol
prepared statement components and stores them in a common structure.
The mxs_mysql_get_command extracts the command byte from a GWBUF object
containing a complete MySQL packet.
The firewall uses a bitmask for representing what operations a
particular rule should be applied to. Consquently it cannot use
the query classifier qc_query_op_t enumerator values as such,
as they are consecutive numbers.
The initial setting of sql_mode affects how MaxScale initially
behaves with respect to autocommit.
When 'set sql_mode=[default|oracle];" is encountered, the query
classifier and autocommit modes are adjusted accordingly.
The default sql mode must now be provided explicitly when the query
classifier is setup. This is in preparation for "sql_mode" becoming
a global configuration parameter of MaxScale.
That's where it belongs as it is only the mysql client protocol that
will use it. It's a bit unfortunate that the qc test program compare
now needs to include a file from a protocol module directory, but
the fact is that the query classifier implementation and the test
programs should actually be *under* the mysql client protocol module.
The current sql mode will be tracked in that variable. Since one
thread will handle multiple sessions, we need to track the sql mode
of a session, so that the sql mode of the query classifier can be
set whenever we handle a request of a particular session.
As the sql-mode will be managed by the client protocol, the data
can be private to it as well.
The parser is needed not only by mysql_client but also by the test
program of the qc-plugins, so it need to be available someplace
common.
Not that nice that both a qc-component and mysql_client will include
stuff from server/core/maxscale, but at least temporarily ok.
SetSqlModeParser is a custom parser for detecting "SET SQL_MODE=..."
statements. It will be used in mysql_client and the result will be
used for updating the sql_mode of a session (that is to be added).
Thereafter, whenever a statement arrives, the value of that sql_mode
will be used for setting the mode of the query_classifier.
A custom parser for detecting "set sql_mode=ORACLE" is needed
and writing that is C++ is more convenient than writing it in
C. Consequently, so as to be able to use that parser, mysql_client
must be compiled as C++.
The sql mode is now a property of the info object used for storing
parsing related information. It is initialized with the value of the
sql mode qc_sqlite was initialized with.
This will be further changed so that the mode can be adjusted at
runtime so that the sql mode can be the property of a session. That
is, once set it will affect all future parsing for that session.
