Alias handling must be made so that in a subselect, aliases created
in an outer select are available, but aliases created in another
subselect are not.
The sqlite3 initialization is done a bit more properly now.
It is also ensured that issues are logged at most once, even
if a statement is parsed twice.
All callbacks called by sqlite now only access the thread specific
QcSqliteInfo and call the corresponding function on that instance.
This is the first step in making qc_sqlite exception safe from the
point of view of sqlite3.
As the diff is confusing, basically the ONLY thing that has been
done is:
BEFORE:
-------
class QcSqliteInfo
{
...
};
static void some_helper(...) { ... }
void mxs_someCallback(...)
{
QC_TRACE();
QcSqliteInfo* info = this_thread.pInfo;
ss_dassert(info);
info->m_status = ...;
some_helper(info, ...);
}
AFTER:
------
class QcSqliteInfo
{
...
void some_helper(...) { ... }
void mxs_someCallback(...)
{
m_status = ...;
some_helper(this, ...);
}
};
void mxs_someCallback(...)
{
QC_TRACE();
QcSqliteInfo* pInfo = this_thread.pInfo;
ss_dassert(pInfo);
pInfo->mxs_someCallback(...);
}
With this change, for a statement like
SELECT t2.a FROM t1 t2;
the affected field is reported as t1.a and not as t2.a, as it
was before.
For a statement like
SELECT t.f FROM d.t;
qc_mysqlembedded will now return "d.t.f" as the affected field,
while qc_sqlite will still return "t.f" as both implementations did
before. In qc_mysqlembedded's case that is a side-effect of the
alias handling. To get qc_sqlite to return the same (which would
be good), the table names would have to be collected in a smarter
way than they are now.
Alias names for tables are now collected, so that the true
table name of a referred to field can be reported. That modification
will be made in a subsequent commit.
If a particular table appears in a statement multiple times,
qc_get_table_names will report it as many times as it appears.
Each name should be reported just once. Same applies for
database names.
The update_names() will have to be updated to take a possible alias
name as well. That needs to be tracked inside QcSqliteInfo, so that
when there is a statement like "select t2.a from t1 t2" we report
the field as t1.a and not as t2.a.
The structure for storing statement information is now a C++ class.
At least initially it will not be turned into a full-fledged class
that would contain all functionality, but the code will be a mishmash
of C and C++.
- Fields in CTEs are marked as being used in subselects.
- In qc_mysqlembedded all selects must be walked if CTE is present.
- In qc_sqlite unions need special handling.
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.
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.
In PL/SQL BEGIN starts a block (i.e. not a transaction). Whenever we
see that, we assume it is such a block, consume all input and set the
type to QUERY_TYPE_WRITE to ensure it goes to master.
Both 10.3 and Oracle support sequence pseudo colums and corresponding
functions. Getting the next number in the sequence is in both cases
obtained using nextval/nextval() but the current number is in Oracle
obtained using currval/currval() and in 10.3 using lastval/lastval().
These fields/functions are now ignored, in the sense that they will
not show up in the field/function infos. However, they will cause the
type mask of the statement to contain the bit QUERY_TYPE_WRITE so that
statements accessing the sequence will always be sent to the master.
Oracle SQL accepts statements like
PREPARE stmt FROM 'INSERT INTO t1 VALUES (:a,:b)';
PREPARE stmt FROM 'INSERT INTO t1 VALUES (:"a",:"b")';
That is, the variable may be surrounded by quotes.
