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Problem:
The logic in store_column_type() with a switch on field type was
hard to follow. The part for MEDIUMINT (MYSQL_TYPE_INT24) was not correct.
It erroneously calculated the precision of MEDIUMINT UNSIGNED
as 7 instead of 8.
A similar hard-to-follow switch doing some type specific calculations
resided in adjust_max_effective_column_length(). It was also wrong for
MEDIUMINT (reported as a separate issue in MDEV-15946).
Solution:
1. Introducing a new class Information_schema_numeric_attributes
2. Adding a new virtual method Field::information_schema_numeric_attributes()
3. Splitting the logic in store_column_type() into virtual
implementations of information_schema_numeric_attributes().
4. In order to avoid adding duplicate code for the integer data types,
adding a new virtual method Field_int::numeric_precision(),
which returns the number of digits.
Additional changes:
1. Adding the "const" qualifier to Field::max_display_length()
2. Moving the code from adjust_max_effective_column_length()
directly to Field::max_display_length().
There was no any sense to have two implementations:
- a set of wrong virtual implementations for Field_xxx::max_display_length()
- additional code in adjust_max_effective_column_length() fixing
bad results of Field_xxx::max_display_length()
This change is safe:
- The code using Field::max_display_length()
in field.cc, sql_show.cc, sql_type.cc is not affected.
- The code in rpl_utility.cc is also not affected.
See a new DBUG_ASSSERT and new comments explaining why.
In the new reduction, Field_xxx::max_display_length() returns
correct results for all integer types (except MEDIUMINT, see below).
Putting implementations of numeric_precision() and max_display_length()
near each other in field.h made the logic much clearer and thus
helped to reveal bad results for Field_medium::max_display_length(),
which returns 9 instead of 8 for signed MEDIUMINT fields.
This problem will be addressed separately (MDEV-15946).
Note, this change is also useful for pluggable data types (see MDEV-4912),
as now a user defined Field_xxx has a way to control what's returned
in INFORMATION_SCHEMA.COLUMNS.NUMERIC_PRECISION and
INFORMATION_SCHEMA.COLUMNS.NUMERIC_SCALE by implementing
a desired behavior in Field_xxx::information_schema_numeric_attributes().
2008-02-29 Matthias Leich
=========================
1. The testsuite "funcs_1" is mostly intended for additional (compared
to the common regression tests stored in mysql-test/t) checks
of features (VIEWS, INFORMATION_SCHEMA, STORED PROCEDURES,...)
introduced with MySQL 5.0.
2. There were some extensions of this suite when new information_schema
views were introduced. But in most cases the tests for these views
were stored within the regression testsuite (mysql-test/t).
INFORMATION_SCHEMA views introduced with MySQL 5.1
==================================================
ENGINES (partially tested here)
EVENTS (partially tested here)
FILES
GLOBAL_STATUS
GLOBAL_VARIABLES
PARTITIONS
PLUGINS
PROCESSLIST (full tested here)
PROFILING
REFERENTIAL_CONSTRAINTS
SESSION_STATUS
SESSION_VARIABLES
3. Some hints for maintainers of this suite:
- SHOW TABLES ... LIKE '<pattern>'
does a case sensitive comparison between the tablename and
the pattern.
The names of the tables within the informationschema are in uppercase.
So please use something like
SHOW TABLES FOR information_schema LIKE 'TABLES'
when you intend to get the same non empty result set on OS with and
without case sensitive filesystems and default configuration.
- The name of the data dictionary is 'information_schema' (lowercase).
- Server on OS with filesystem with case sensitive filenames
(= The files 'abc' and 'Abc' can coexist.)
+ default configuration
Example of behaviour:
DROP DATABASE information_schema;
ERROR 42000: Access denied for user ... to database 'information_schema'
DROP DATABASE INFORMATION_SCHEMA;
ERROR 42000: Access denied for user ... to database 'INFORMATION_SCHEMA'
- Try to unify results by
--replace_result $engine_type <engine_to_be_tested>
if we could expect that the results for storage engine variants of a
test differ only in the engine names.
This makes future maintenance easier.
- Avoid the use of include/show_msg*.inc.
They produce "SQL" noise which annoys during server debugging and can be
easy replaced by "--echo ...".