mariadb/sql/unireg.h
Nikita Malyavin e2e79ad916 MDEV-35915 Implement Global temporary tables
Global temporary table (GTT) is a table with globally defined metadata,
but per-session data.

That is, the life duration of this data is limited with session
duration. Here we have two options:

1. ON COMMIT DELETE ROWS: a default option. The life duration of data is
transaction duration.
2. ON COMMIT PRESERVE ROWS: The life duration of data is session
duration.

# Implementation

The implementation consists of the following fundamental parts.

## Part 1: CREATE TABLE + frm format

1. Store GLOBAL TEMPORARY and ON COMMIT bits in
   create_info->table_options
2. Store higher word of create_info->table_options in frm header
3. Also disallow ON COMMIT keyword for (local) temporary tables

As a result, the bits will be available in share->db_create_options.

New Table_type enum element: TABLE_TYPE_GLOBAL_TEMPORARY (datadict.h)

## Part 2: open_table: a local data table is created on demand

On open, a session-local temporary table copy is created from a global
TABLE_SHARE. Let us refer to the former as "local data table of GTT",
and the latter as "global metadata table of GTT".

There is a number of cases, when a global metadata table is opened
instead, like ALTER, DROP, SHOW CREATE

A local data table holds:

1. A reference to that share, and holds the increased
tdc reference count.
2. An explicit MDL lock to the duration of local copy's
existence.

While at least one local data table exists
(2) guarantees that ALTER, DROP or RENAME will not happen.
(1) guarantees that a global metadata table will not be flushed

At an implementation level, a local data table is a temporary table,
invisible for a user and augmented with (1) and (2).

The reference and lock are released upon dropping this local data table,
which happens due to:
a) TRUNCATE TABLE
b) Connection close
c) If ON COMMIT DELETE ROWS is used, then on transaction commit/rollback

## Part 3: ALTER, DROP, RENAME

These operations always open a real global temporary table.

ALTER, RENAME and DROP TABLE require all local data tables to be
destroyed, thus, having no references to a modified/deleted table.
For that, they:
1. acquire an EXCLUSIVE MDL lock. To match oracle behavior,
lock_wait_timeout is 0 in ALTER TABLE.
2. Check that there is no matching local temporary table in the same
connection (which is not guaranteed by 1)

## Part 4 ON COMMIT DELETE ROWS

This clause is assumed by default, i.e. it is implicit.

When ON COMMIT DELETE ROWS, the local data table is dropped on
commit/rollback.

On table open, global_temporary_tables handlerton is injected,
implementing this behavior.

# Limitations

The following is forbidden for GTT:
system versioning
partitioning
fk
ONLINE ALTER
CREATE GLOBAL TEMPORARY under LOCK TABLES
FLUSH TABLE on Global temporary table is no-op for now

# Refactorings, details

1. Extract drop_tmp_table_share (temporary_tables.cc)
2. Extract THD::open_temporary_table_impl (temporary_tables.cc)
3. information_schema support:
 x) "GLOBAL TEMPORARY" type is show in information_schema.tables
 y) an artifical temporary table is hidden from SHOW TABLE STATUS

4. VIEWs are supported.
5. AS SELECT support

 x) Made in Oracle style, so that the data is only inserted in the
 session that creates GTT
 y) ON COMMIT DELETE ROWS inserts the data for real, and then deletes
 the data table on implicit commit

6. CREATE TABLE ... LIKE is supported.

7. Replication support
 x) Set share->table_creation_was_logged to 0 to make the table ignored
 for replication.
 y) Statements with GTT involved will be logged in Row-based style
 (RBR)
 z) Global temporary table creation and alter/drop will be logged.
2025-08-12 17:54:52 +02:00

238 lines
7.9 KiB
C

#ifndef UNIREG_INCLUDED
#define UNIREG_INCLUDED
/*
Copyright (c) 2000, 2011, Oracle and/or its affiliates.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
#include <mysql_version.h> /* FRM_VER */
/* Extra functions used by unireg library */
#ifndef NO_ALARM_LOOP
#define NO_ALARM_LOOP /* lib5 and popen can't use alarm */
#endif
/* These paths are converted to other systems (WIN95) before use */
#define LANGUAGE "english/"
#define ERRMSG_FILE "errmsg.sys"
#define TEMP_PREFIX "MY"
#define LOG_PREFIX "ML"
#define PROGDIR "bin/"
#ifndef MYSQL_DATADIR
#define MYSQL_DATADIR "data/"
#endif
#ifndef SHAREDIR
#define SHAREDIR "share/"
#endif
#ifndef PLUGINDIR
#define PLUGINDIR "lib/plugin"
#endif
#define MAX_ERROR_RANGES 4 /* 1000-2000, 2000-3000, 3000-4000, 4000-5000 */
#define ERRORS_PER_RANGE 1000
#define DEFAULT_ERRMSGS my_default_lc_messages->errmsgs->errmsgs
#define CURRENT_THD_ERRMSGS (current_thd)->variables.errmsgs
#ifndef mysqld_error_find_printf_error_used
#define ER_DEFAULT(X) DEFAULT_ERRMSGS[((X)-ER_ERROR_FIRST) / ERRORS_PER_RANGE][(X)% ERRORS_PER_RANGE]
#define ER_THD(thd,X) ((thd)->variables.errmsgs[((X)-ER_ERROR_FIRST) / ERRORS_PER_RANGE][(X) % ERRORS_PER_RANGE])
#define ER(X) ER_THD(current_thd, (X))
#endif
#define ER_THD_OR_DEFAULT(thd,X) ((thd) ? ER_THD(thd, (X)) : ER_DEFAULT(X))
#define SPECIAL_USE_LOCKS 1 /* Lock used databases */
#define SPECIAL_NO_NEW_FUNC 2 /* Skip new functions */
#define SPECIAL_SKIP_SHOW_DB 4 /* Don't allow 'show db' */
#define SPECIAL_WAIT_IF_LOCKED 8 /* Wait if locked database */
#define SPECIAL_SAME_DB_NAME 16 /* form name = file name */
#define SPECIAL_ENGLISH 32 /* English error messages */
#define SPECIAL_NO_RESOLVE 64 /* Obsolete */
#define SPECIAL_NO_PRIOR 128 /* Obsolete */
#define SPECIAL_BIG_SELECTS 256 /* Don't use heap tables */
#define SPECIAL_NO_HOST_CACHE 512 /* Don't cache hosts */
#define SPECIAL_SHORT_LOG_FORMAT 1024
#define SPECIAL_SAFE_MODE 2048
#define SPECIAL_LOG_QUERIES_NOT_USING_INDEXES 4096 /* Obsolete */
/* Extern defines */
#define store_record(A,B) memcpy((A)->B,(A)->record[0],(size_t) (A)->s->reclength)
#define restore_record(A,B) memcpy((A)->record[0],(A)->B,(size_t) (A)->s->reclength)
#define cmp_record(A,B) memcmp((A)->record[0],(A)->B,(size_t) (A)->s->reclength)
#define empty_record(A) { \
restore_record((A),s->default_values); \
if ((A)->s->null_bytes) \
bfill((A)->null_flags,(A)->s->null_bytes,255); \
}
/* Defines for use with openfrm, openprt and openfrd */
#define READ_ALL (1 << 0) /* openfrm: Read all parameters */
#define EXTRA_RECORD (1 << 3) /* Reserve space for an extra record */
#define DELAYED_OPEN (1 << 12) /* Open table later */
#define OPEN_VIEW_NO_PARSE (1 << 14) /* Open frm only if it's a view,
but do not parse view itself */
/**
This flag is used in function get_all_tables() which fills
I_S tables with data which are retrieved from frm files and storage engine
The flag means that we need to open FRM file only to get necessary data.
*/
#define OPEN_FRM_FILE_ONLY (1 << 15)
/**
This flag is used in function get_all_tables() which fills
I_S tables with data which are retrieved from frm files and storage engine
The flag means that we need to process tables only to get necessary data.
Views are not processed.
*/
#define OPEN_TABLE_ONLY (1 << 16)
/**
This flag is used in function get_all_tables() which fills
I_S tables with data which are retrieved from frm files and storage engine
The flag means that we need to process views only to get necessary data.
Tables are not processed.
*/
#define OPEN_VIEW_ONLY (1 << 17)
/**
This flag is used in function get_all_tables() which fills
I_S tables with data which are retrieved from frm files and storage engine.
The flag means that we need to open a view using
open_normal_and_derived_tables() function.
*/
#define OPEN_VIEW_FULL (1 << 18)
/**
This flag is used in function get_all_tables() which fills
I_S tables with data which are retrieved from frm files and storage engine.
The flag means that I_S table uses optimization algorithm.
*/
#define OPTIMIZE_I_S_TABLE (1 << 19)
/**
This flag is used to instruct tdc_open_view() to check metadata version.
*/
#define CHECK_METADATA_VERSION (1 << 20)
/*
The flag means that we need to process trigger files only.
*/
#define OPEN_TRIGGER_ONLY (1 << 21)
/**
This flag is used in information schema to determine if handling function
can treat open result extensively and provide some user output even if
table open fails.
*/
#define I_S_EXTENDED_ERROR_HANDLING (1 << 22)
/** This TABLE handle is not suitable for cache and should not be reused. */
#define OPEN_NO_CACHE (1 << 23)
/*
Minimum length pattern before Turbo Boyer-Moore is used
for SELECT "text" LIKE "%pattern%", excluding the two
wildcards in class Item_func_like.
*/
#define MIN_TURBOBM_PATTERN_LEN 3
/*
Defines for binary logging.
Do not decrease the value of BIN_LOG_HEADER_SIZE.
Do not even increase it before checking code.
*/
#define BIN_LOG_HEADER_SIZE 4
#define DEFAULT_KEY_CACHE_NAME "default"
/* Include prototypes for unireg */
#include "mysqld_error.h"
#include "structs.h" /* All structs we need */
#include "sql_list.h" /* List<> */
#include "field.h" /* Create_field */
/*
Types of values in the MariaDB extra2 frm segment.
Each value is written as
type: 1 byte
length: 1 byte (1..255) or \0 and 2 bytes.
binary value of the 'length' bytes.
Older MariaDB servers can ignore values of unknown types if
the type code is less than 128 (EXTRA2_ENGINE_IMPORTANT).
Otherwise older (but newer than 10.0.1) servers are required
to report an error.
*/
enum extra2_frm_value_type {
EXTRA2_TABLEDEF_VERSION=0,
EXTRA2_DEFAULT_PART_ENGINE=1,
EXTRA2_GIS=2,
EXTRA2_APPLICATION_TIME_PERIOD=3,
EXTRA2_PERIOD_FOR_SYSTEM_TIME=4,
EXTRA2_INDEX_FLAGS=5,
#define EXTRA2_ENGINE_IMPORTANT 128
EXTRA2_ENGINE_TABLEOPTS=128,
EXTRA2_FIELD_FLAGS=129,
EXTRA2_FIELD_DATA_TYPE_INFO=130,
EXTRA2_PERIOD_WITHOUT_OVERLAPS=131,
};
enum extra2_field_flags {
VERS_OPTIMIZED_UPDATE= 1 << INVISIBLE_MAX_BITS,
};
enum extra2_index_flags {
EXTRA2_DEFAULT_INDEX_FLAGS,
EXTRA2_IGNORED_KEY
};
static inline size_t extra2_read_len(const uchar **extra2, const uchar *end)
{
size_t length= *(*extra2)++;
if (length)
return length;
if ((*extra2) + 2 >= end)
return 0;
length= uint2korr(*extra2);
(*extra2)+= 2;
if (length < 256 || *extra2 + length > end)
return 0;
return length;
}
LEX_CUSTRING build_frm_image(THD *thd, const LEX_CSTRING &table,
HA_CREATE_INFO *create_info,
List<Create_field> &create_fields,
uint keys, KEY *key_info, handler *db_file);
#define FRM_HEADER_SIZE 64
#define FRM_FORMINFO_SIZE 288
#define FRM_MAX_SIZE (1024*1024)
static inline bool is_binary_frm_header(const uchar *head)
{
return head[0] == 254
&& head[1] == 1
&& head[2] >= FRM_VER
&& head[2] <= FRM_VER_CURRENT;
}
#endif