This patch implements support for implicit query block (QB) names in
optimizer hints, allowing hints to reference query blocks and tables
within derived tables, views and CTEs without requiring explicit
QB_NAME hints.
Examples.
-- Addressing a table inside a derived table using implicit QB name
select /*+ no_index(t1@dt) */ *
from (select * from t1 where a > 10) as DT;
-- this is an equivalent to:
select /*+ no_index(t1@dt) */ * from
(select /*+ qb_name(dt)*/ * from t1 where a > 10) as DT;
-- Addressing a query block corresponding to the derived table
select /*+ no_bnl(@dt) */ *
from (select * from t1, t2 where t.1.a > t2.a) as DT;
-- View
create view v1 as select * from t1 where a > 10 and b > 100;
-- referencing a table inside a view by implicit QB name:
select /*+ index_merge(t1@v1 idx_a, idx_b) */ *
from v1, t2 where v1.a = t2.a;
-- equivalent to:
create view v1 as select /*+ qb_name(qb_v1) */ *
from t1 where a > 10 and b > 100;
select /*+ index_merge(t1@qb_v1 idx_a, idx_b) */ *
from v1, t2 where v1.a = t2.a;
-- CTE
with aless100 as (select a from t1 where b <100)
select /*+ index(t1@aless100) */ * from aless100;
-- equivalent to:
with aless100 as (select /*+ qb_name(aless100) */ a from t1 where b <100)
select /*+ index(t1@aless100) */ * from aless100;
Limitations:
- Only SELECT statements support implicit QB names. DML operations
(UPDATE, DELETE, INSERT) only support explicit QB names
Remove the unscoped #pragma GCC diagnostic ignored
"-Wdeprecated-declarations" from include/violite.h and replace all
sprintf/vsprintf calls with snprintf/vsnprintf across the codebase.
Where possible, pass actual buffer sizes as function parameters
instead of using hardcoded constants or recomputing strlen().
Notable API changes:
- get_date(): added to_len parameter for buffer size
- nice_time(), end_timer() in client/mysql.cc: added buff_size
- generate_new_name(): added name_size parameter
- calc_md5(): added buffer_size parameter (fixes off-by-one)
- MD5_HASH_TO_STRING macro: added _size parameter
- Added MYSQL_UDF_MAX_RESULT_LENGTH constant in mysql_com.h
Also fixed a pre-existing bug in sql/rpl_mi.cc where the ellipsis
"..." was written to the wrong buffer (dbuff instead of buff).
Vendored code is excluded: extra/readline, extra/wolfssl,
wsrep-lib, libmariadb, storage/mroonga/vendor, zlib.
Originally two MDL_EXCLUSIVE are used for pure alias of derived table
and its schema which is empty db name. It is concurrency performance
overhead and there is no obvious reason why such MDL should exist.
MDEV-33985 changed pure alias check from `db.str` to `db.length` and
that allowed `empty_c_string` to be pure alias too. It is important
for MDEV-33985 fix with sequences. Now such kind of pure alias skips
MDL initialization and thus derived table fails falsely on BACKUP
namespace as it is default namespace for 0-filled structure (see TODO
comments).
The fix a) keeps MDL_NOT_INITIALIZED for uninitialized MDL and that
was the consequence of MDL_INTENTION_EXCLUSIVE value 0 (see TODO
comment).
And b) does not update MDL type for pure alias when view is
initialized, so it is MDL_NOT_INITIALIZED. `lock_table_names()` code
naturally skips such kind of MDL with (mdl_request.type <
MDL_SHARED_UPGRADABLE) condition when processing tables list.
Optimization in st_select_lex_unit::prepare() removes ORDER BY for
certain subqueries. That excludes ORDER BY items from being fixed, but
sl->window_funcs still contains window function items and those
related to optimized out ORDER BY are unfixed. The error about missing
window spec is thrown when the item is fixed. Hence we get redundant
processing of window function items without checking window spec
existence.
The fix removes the related window function items when ORDER BY is
optimized out. ORDER accumulates window_funcs at parser stage which
are then removed from SELECT_LEX::window_funcs. The fix also updates
similar optimization in mysql_make_view().
MDEV-28650 (7a88776dc1) fixed the case when the DEFAULT flag is
inside the table definition but it can be also in DML command. When we
assign it from the table definition in mysql_make_view() we lose it in
the current command.
The fix does disjunction assignment to keep both values. It is
signalling DML_prelocking_strategy::handle_table() to call
add_internal_tables(), so it will correctly open associated sequence
table.
* rename to follow the standard vprintf name convention
* remove `(LEX_CSTRING*) &lex_string` casts
* remove some redundant casts too
* LEX_CSTRING -> Lex_ident_db in path
* Hash_set<Sroutine_hash_entry>
* move assert out of the loop
* some comments and whitespace changes
don't create a permanent stack of paths on the heap and in THD.
Do it on the stack like for sql_mode, sctx, abort_on_warning, and
other THD properties that often need to be changed temporarily.
Fix Sql_path constructor.
Definition
==========
Implement the SET PATH statement.
```
SET PATH 'schema1, schema2, schema3';
```
Function
--------
In MariaDB, the SQL-path will also be used to lookup packages in
package routine invocations, so the following script:
SET PATH 'sys';
SELECT UTL_ENCODE.BASE64_DECODE('data');
invokes SYS.UTL_ENCODE.BASE64_DECODE('data'), i.e. the function
BASE64_DECODE() in the packge UTL_ENCODE in the database SYS
(if such package and package routine exist).
MariaDB implementation details
------------------------------
The ticket's requirement stated the grammar should support delimited
identifiers with backticks or double quotes within the string quote,
ie: the single tick. A simple parser was implemented to handle this
requirement in Sql_path::from_text.
Only 16 schemas are supported per session - we do not want too many
schemas in the path anyway since it will impact performance. This also
means that the path cache is a simple static array for easier memory
management.
default_used was missing as view is parsed on its own
lex. extend_table_list() decides maybe_need_prelocking based on
default_used and prelocking_strategy->handle_table() was skipped for
view, so internal_tables was not updated (they could be stale from
previous statement).
Query blocks have implicit names, such as `select#1`, formulated
by appending their select number to the string `select#`. This patch
allows hints to scope their applicability by implicit query block
name. For example,
SELECT /*+ JOIN_ORDER(@`select#2` t1, t2) */ ...
@`select#2` is an implicit query block name. Users can control hint
applicability per query block without first naming the blocks with
QB_NAME().
Hints may now be specified within VIEWs during their creation and
they are applied locally within that VIEW's scope. For example,
CREATE VIEW v1 AS
SELECT /*+ IGNORE_INDEX(t1 idx1) */ FROM t1 ... GROUP BY ... HAVING ...
In many cases and for some parts of the VIEW, the query plan
doesn't really depend on how the VIEW is used, so it makes sense
to control a part of the query plan from the VIEW definition.
Implicit names are not yet supported in VIEWs. Attempting to create
a VIEW with an implicit name reference will cause the server to create
the VIEW, but it will emit a warning and exclude that hint from the query.
This patch adds support for SYS_REFCURSOR (a weakly typed cursor)
for both sql_mode=ORACLE and sql_mode=DEFAULT.
Works as a regular stored routine variable, parameter and return value:
- can be passed as an IN parameter to stored functions and procedures
- can be passed as an INOUT and OUT parameter to stored procedures
- can be returned from a stored function
Note, strongly typed REF CURSOR will be added separately.
Note, to maintain dependencies easier, some parts of sql_class.h
and item.h were moved to new header files:
- select_results.h:
class select_result_sink
class select_result
class select_result_interceptor
- sp_cursor.h:
class sp_cursor_statistics
class sp_cursor
- sp_rcontext_handler.h
class Sp_rcontext_handler and its descendants
The implementation consists of the following parts:
- A new class sp_cursor_array deriving from Dynamic_array
- A new class Statement_rcontext which contains data shared
between sub-statements of a compound statement.
It has a member m_statement_cursors of the sp_cursor_array data type,
as well as open cursor counter. THD inherits from Statement_rcontext.
- A new data type handler Type_handler_sys_refcursor in plugins/type_cursor/
It is designed to store uint16 references -
positions of the cursor in THD::m_statement_cursors.
- Type_handler_sys_refcursor suppresses some derived numeric features.
When a SYS_REFCURSOR variable is used as an integer an error is raised.
- A new abstract class sp_instr_fetch_cursor. It's needed to share
the common code between "OPEN cur" (for static cursors) and
"OPER cur FOR stmt" (for SYS_REFCURSORs).
- New sp_instr classes:
* sp_instr_copen_by_ref - OPEN sys_ref_curor FOR stmt;
* sp_instr_cfetch_by_ref - FETCH sys_ref_cursor INTO targets;
* sp_instr_cclose_by_ref - CLOSE sys_ref_cursor;
* sp_instr_destruct_variable - to destruct SYS_REFCURSOR variables when
the execution goes out of the BEGIN..END block
where SYS_REFCURSOR variables are declared.
- New methods in LEX:
* sp_open_cursor_for_stmt - handles "OPEN sys_ref_cursor FOR stmt".
* sp_add_instr_fetch_cursor - "FETCH cur INTO targets" for both
static cursors and SYS_REFCURSORs.
* sp_close - handles "CLOSE cur" both for static cursors and SYS_REFCURSORs.
- Changes in cursor functions to handle both static cursors and SYS_REFCURSORs:
* Item_func_cursor_isopen
* Item_func_cursor_found
* Item_func_cursor_notfound
* Item_func_cursor_rowcount
- A new system variable @@max_open_cursors - to limit the number
of cursors (static and SYS_REFCURSORs) opened at the same time.
Its allowed range is [0-65536], with 50 by default.
- A new virtual method Type_handler::can_return_bool() telling
if calling item->val_bool() is allowed for Items of this data type,
or if otherwise the "Illegal parameter for operation" error should be raised
at fix_fields() time.
- New methods in Sp_rcontext_handler:
* get_cursor()
* get_cursor_by_ref()
- A new class Sp_rcontext_handler_statement to handle top level statement
wide cursors which are shared by all substatements.
- A new virtual method expr_event_handler() in classes Item and Field.
It's needed to close (and make available for a new OPEN)
unused THD::m_statement_cursors elements which do not have any references
any more. It can happen in various moments in time, e.g.
* after evaluation parameters of an SQL routine
* after assigning a cursor expression into a SYS_REFCURSOR variable
* when leaving a BEGIN..END block with SYS_REFCURSOR variables
* after setting OUT/INOUT routine actual parameters from formal
parameters.
Problem was incorrect handling of partitioned tables,
because db_type == DB_TYPE_PARTITION_DB
wsrep_should_replicate_ddl incorrectly marked
DDL as not replicatable. However, in partitioned
tables we should check implementing storage engine
from table->file->partition_ht() if available because
if partition handler is InnoDB all DDL should be allowed
even with wsrep_strict_ddl. For other storage engines
DDL should not be allowed and error should be issued.
This is 10.5 version of the fix.
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>
create templates
thd->alloc<X>(n) to use instead of (X*)thd->alloc(sizeof(X)*n)
and the same for thd->calloc(). By the default the type is char,
so old usage of thd->alloc(size) works too.
Fix for MDEV-31466 - add optional derived table column names.
Column names within a SELECT_LEX structure can be left in a non-reparsable
state (as printed out from *::print) after JOIN::prepare. This caused
an incorrect view definition to be written into the .FRM file.
Fixed by resetting item list names in SELECT_LEX structures representing
derived tables before writing out the view definition.
Reviewed by Igor Babaev (igor@mariadb.com)
This task is to ensure we have a clear definition and rules of how to
repair or optimize a table.
The rules are:
- REPAIR should be used with tables that are crashed and are
unreadable (hardware issues with not readable blocks, blocks with
'unexpected data' etc)
- OPTIMIZE table should be used to optimize the storage layout for the
table (recover space for delete rows and optimize the index
structure.
- ALTER TABLE table_name FORCE should be used to rebuild the .frm file
(the table definition) and the table (with the original table row
format). If the table is from and older MariaDB/MySQL release with a
different storage format, it will convert the data to the new
format. ALTER TABLE ... FORCE is used as part of mariadb-upgrade
Here follows some more background:
The 3 ways to repair a table are:
1) ALTER TABLE table_name FORCE" (not other options).
As an alias we allow: "ALTER TABLE table_name ENGINE=original_engine"
2) "REPAIR TABLE" (without FORCE)
3) "OPTIMIZE TABLE"
All of the above commands will optimize row space usage (which means that
space will be needed to hold a temporary copy of the table) and
re-generate all indexes. They will also try to replicate the original
table definition as exact as possible.
For ALTER TABLE and "REPAIR TABLE without FORCE", the following will hold:
If the table is from an older MariaDB version and data conversion is
needed (for example for old type HASH columns, MySQL JSON type or new
TIMESTAMP format) "ALTER TABLE table_name FORCE, algorithm=COPY" will be
used.
The differences between the algorithms are
1) Will use the fastest algorithm the engine supports to do a full repair
of the table (except if data conversions are is needed).
2) Will use the storage engine internal REPAIR facility (MyISAM, Aria).
If the engine does not support REPAIR then
"ALTER TABLE FORCE, ALGORITHM=COPY" will be used.
If there was data incompatibilities (which means that FORCE was used)
then there will be a warning after REPAIR that ALTER TABLE FORCE is
still needed.
The reason for this is that REPAIR may be able to go around data
errors (wrong incompatible data, crashed or unreadable sectors) that
ALTER TABLE cannot do.
3) Will use the storage engine internal OPTIMIZE. If engine does not
support optimize, then "ALTER TABLE FORCE" is used.
The above will ensure that ALTER TABLE FORCE is able to
correct almost any errors in the row or index data. In case of
corrupted blocks then REPAIR possible followed by ALTER TABLE is needed.
This is important as mariadb-upgrade executes ALTER TABLE table_name
FORCE for any table that must be re-created.
Bugs fixed with InnoDB tables when using ALTER TABLE FORCE:
- No error for INNODB_DEFAULT_ROW_FORMAT=COMPACT even if row length
would be too wide. (Independent of innodb_strict_mode).
- Tables using symlinks will be symlinked after any of the above commands
(Independent of the setting of --symbolic-links)
If one specifies an algorithm together with ALTER TABLE FORCE, things
will work as before (except if data conversion is required as then
the COPY algorithm is enforced).
ALTER TABLE .. OPTIMIZE ALL PARTITIONS will work as before.
Other things:
- FORCE argument added to REPAIR to allow one to first run internal
repair to fix damaged blocks and then follow it with ALTER TABLE.
- REPAIR will not update frm_version if ha_check_for_upgrade() finds
that table is still incompatible with current version. In this case the
REPAIR will end with an error.
- REPAIR for storage engines that does not have native repair, like InnoDB,
is now using ALTER TABLE FORCE.
- REPAIR csv-table USE_FRM now works.
- It did not work before as CSV tables had extension list in wrong
order.
- Default error messages length for %M increased from 128 to 256 to not
cut information from REPAIR.
- Documented HA_ADMIN_XX variables related to repair.
- Added HA_ADMIN_NEEDS_DATA_CONVERSION to signal that we have to
do data conversions when converting the table (and thus ALTER TABLE
copy algorithm is needed).
- Fixed typo in error message (caused test changes).
This patch also fixes:
MDEV-33050 Build-in schemas like oracle_schema are accent insensitive
MDEV-33084 LASTVAL(t1) and LASTVAL(T1) do not work well with lower-case-table-names=0
MDEV-33085 Tables T1 and t1 do not work well with ENGINE=CSV and lower-case-table-names=0
MDEV-33086 SHOW OPEN TABLES IN DB1 -- is case insensitive with lower-case-table-names=0
MDEV-33088 Cannot create triggers in the database `MYSQL`
MDEV-33103 LOCK TABLE t1 AS t2 -- alias is not case sensitive with lower-case-table-names=0
MDEV-33109 DROP DATABASE MYSQL -- does not drop SP with lower-case-table-names=0
MDEV-33110 HANDLER commands are case insensitive with lower-case-table-names=0
MDEV-33119 User is case insensitive in INFORMATION_SCHEMA.VIEWS
MDEV-33120 System log table names are case insensitive with lower-cast-table-names=0
- Removing the virtual function strnncoll() from MY_COLLATION_HANDLER
- Adding a wrapper function CHARSET_INFO::streq(), to compare
two strings for equality. For now it calls strnncoll() internally.
In the future it will turn into a virtual function.
- Adding new accent sensitive case insensitive collations:
- utf8mb4_general1400_as_ci
- utf8mb3_general1400_as_ci
They implement accent sensitive case insensitive comparison.
The weight of a character is equal to the code point of its
upper case variant. These collations use Unicode-14.0.0 casefolding data.
The result of
my_charset_utf8mb3_general1400_as_ci.strcoll()
is very close to the former
my_charset_utf8mb3_general_ci.strcasecmp()
There is only a difference in a couple dozen rare characters, because:
- the switch from "tolower" to "toupper" comparison, to make
utf8mb3_general1400_as_ci closer to utf8mb3_general_ci
- the switch from Unicode-3.0.0 to Unicode-14.0.0
This difference should be tolarable. See the list of affected
characters in the MDEV description.
Note, utf8mb4_general1400_as_ci correctly handles non-BMP characters!
Unlike utf8mb4_general_ci, it does not treat all BMP characters
as equal.
- Adding classes representing names of the file based database objects:
Lex_ident_db
Lex_ident_table
Lex_ident_trigger
Their comparison collation depends on the underlying
file system case sensitivity and on --lower-case-table-names
and can be either my_charset_bin or my_charset_utf8mb3_general1400_as_ci.
- Adding classes representing names of other database objects,
whose names have case insensitive comparison style,
using my_charset_utf8mb3_general1400_as_ci:
Lex_ident_column
Lex_ident_sys_var
Lex_ident_user_var
Lex_ident_sp_var
Lex_ident_ps
Lex_ident_i_s_table
Lex_ident_window
Lex_ident_func
Lex_ident_partition
Lex_ident_with_element
Lex_ident_rpl_filter
Lex_ident_master_info
Lex_ident_host
Lex_ident_locale
Lex_ident_plugin
Lex_ident_engine
Lex_ident_server
Lex_ident_savepoint
Lex_ident_charset
engine_option_value::Name
- All the mentioned Lex_ident_xxx classes implement a method streq():
if (ident1.streq(ident2))
do_equal();
This method works as a wrapper for CHARSET_INFO::streq().
- Changing a lot of "LEX_CSTRING name" to "Lex_ident_xxx name"
in class members and in function/method parameters.
- Replacing all calls like
system_charset_info->coll->strcasecmp(ident1, ident2)
to
ident1.streq(ident2)
- Taking advantage of the c++11 user defined literal operator
for LEX_CSTRING (see m_strings.h) and Lex_ident_xxx (see lex_ident.h)
data types. Use example:
const Lex_ident_column primary_key_name= "PRIMARY"_Lex_ident_column;
is now a shorter version of:
const Lex_ident_column primary_key_name=
Lex_ident_column({STRING_WITH_LEN("PRIMARY")});
