WL#4165 Prepared statements: validation
WL#4166 Prepared statements: automatic re-prepare
Fixes
Bug#27430 Crash in subquery code when in PS and table DDL changed after PREPARE
Bug#27690 Re-execution of prepared statement after table was replaced with a view crashes
Bug#27420 A combination of PS and view operations cause error + assertion on shutdown
The basic idea of the patch is to keep track of table metadata between
prepared statement prepare and execute. If some table used in the statement
has changed, the prepared statement is re-prepared before execution.
See WL#4165 and WL#4166 contents and comments in the code for details
of the implementation.
Mixing aggregate functions and non-grouping columns is not allowed in the
ONLY_FULL_GROUP_BY mode. However in some cases the error wasn't thrown because
of insufficient check.
In order to check more thoroughly the new algorithm employs a list of outer
fields used in a sum function and a SELECT_LEX::full_group_by_flag.
Each non-outer field checked to find out whether it's aggregated or not and
the current select is marked accordingly.
All outer fields that are used under an aggregate function are added to the
Item_sum::outer_fields list and later checked by the Item_sum::check_sum_func
function.
Queries like:
SELECT ROW(1, 2) IN (SELECT t1.a, 2)
FROM t1 GROUP BY t1.a
or
SELECT ROW(1, 2) IN (SELECT t1.a, 2 FROM t2)
FROM t1 GROUP BY t1.a
lead to assertion failure in the
Item_in_subselect::row_value_transformer method in debugging
build, or to unexpected error message in release build:
ERROR 1247 (42S22): Reference '<list ref>' not supported (forward
reference in item list)
Unexpected error message and assertion failure have been
eliminated.
The problem is that passing anything other than a integer to a limit
clause in a prepared statement would fail. This limitation was introduced
to avoid replication problems (e.g: replicating the statement with a
string argument would cause a parse failure in the slave).
The solution is to convert arguments to the limit clause to a integer
value and use this converted value when persisting the query to the log.
NAME_CONST('whatever', -1) * MAX(whatever) bombed since -1 was
not seen as constant, but as FUNCTION_UNARY_MINUS(constant)
while we are at the same time pretending it was a basic const
item. This confused the aggregate handlers in exciting ways.
We now make NAME_CONST() behave more consistently.
between 5.0 and 5.1.
The problem was that in the patch for Bug#11986 it was decided
to store original query in UTF8 encoding for the INFORMATION_SCHEMA.
This approach however turned out to be quite difficult to implement
properly. The main problem is to preserve the same IS-output after
dump/restore.
So, the fix is to rollback to the previous functionality, but also
to fix it to support multi-character-set-queries properly. The idea
is to generate INFORMATION_SCHEMA-query from the item-tree after
parsing view declaration. The IS-query should:
- be completely in UTF8;
- not contain character set introducers.
For more information, see WL4052.
breaks replication
NAME_CONST() didn't replicate constant character set and collation
correctly.
With this fix NAME_CONST() inherits collation from the value argument.
when executed in version 5
Zero fill is a field attribute only. So we can't always
propagate constants for zerofill fields : the values and
expression results don't have that flag.
Fixed by converting the const value to a string and
using that in const propagation when the context allows it.
Disable const propagation for fields with ZEROFILL flag in
all the other cases.
but not collation.
The problem here was that text literals in a view were always
dumped with character set introducer. That lead to loosing
collation information.
The fix is to dump character set introducer only if it was
in the original query. That is now possible because there
is no problem any more of loss of character set of string
literals in views -- after WL#4052 the view is dumped
in the original character set.
or trigger crashes server
Under some circumstances a combination of VIEWs, subselects with outer
references and PS/SP/triggers could lead to use of uninitialized memory
and server crash as a result.
Fixed by changing the code in Item_field::fix_fields() so that in cases
when the field is a VIEW reference, we first check whether the field
is also an outer reference, and mark it appropriately before returning.
The unsignedness of large integer user variables was not being
properly preserved when feeded to prepared statements. This was
happening because the unsigned flags wasn't being updated when
converting the user variable is converted to a parameter.
The solution is to copy the unsigned flag when converting the
user variable to a parameter and take the unsigned flag into
account when converting the integer to a string.
Two disjuncts containing equalities of the form key=const1 and key=const2 can
be merged into one if const1 is equal to const2. To check it the common
collation of the constants were used rather than the collation of the field key.
For example when the default collation of the constants was cases insensitive
while the collation of the field was case sensitive, then two or-ed equality
predicates key='b' and key='B' incorrectly were merged into one f='b'. As a
result ref access was used instead of range access and wrong result sets were
returned in many cases.
Fixed the problem by comparing constant in the or-ed predicate with collation of
the key field.
