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mariadb/storage/innobase/include/db0err.h
Marko Mäkelä b8a6719889 MDEV-26642/MDEV-26643/MDEV-32898 Implement innodb_snapshot_isolation 
https://jepsen.io/analyses/mysql-8.0.34 highlights that the
transaction isolation levels in the InnoDB storage engine do not
correspond to any widely accepted definitions, such as
"Generalized Isolation Level Definitions"
https://pmg.csail.mit.edu/papers/icde00.pdf
(PL-1 = READ UNCOMMITTED, PL-2 = READ COMMITTED, PL-2.99 = REPEATABLE READ,
PL-3 = SERIALIZABLE).
Only READ UNCOMMITTED in InnoDB seems to match the above definition.

The issue is that InnoDB does not detect write/write conflicts
(Section 4.4.3, Definition 6) in the above.

It appears that as soon as we implement write/write conflict detection
(SET SESSION innodb_snapshot_isolation=ON), the default isolation level
(SET TRANSACTION ISOLATION LEVEL REPEATABLE READ) will become
Snapshot Isolation (similar to Postgres), as defined in Section 4.2 of
"A Critique of ANSI SQL Isolation Levels", MSR-TR-95-51, June 1995
https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/tr-95-51.pdf

Locking reads inside InnoDB used to read the latest committed version,
ignoring what should actually be visible to the transaction.
The added test innodb.lock_isolation illustrates this. The statement
	UPDATE t SET a=3 WHERE b=2;
is executed in a transaction that was started before a read view or
a snapshot of the current transaction was created, and committed before
the current transaction attempts to execute
	UPDATE t SET b=3;
If SET innodb_snapshot_isolation=ON is in effect when the second
transaction was started, the second transaction will be aborted with
the error ER_CHECKREAD. By default (innodb_snapshot_isolation=OFF),
the second transaction would execute inconsistently, displaying an
incorrect SELECT COUNT(*) FROM t in its read view.

If innodb_snapshot_isolation=ON, if an attempt to acquire a lock on a
record that does not exist in the current read view is made, an error
DB_RECORD_CHANGED (HA_ERR_RECORD_CHANGED, ER_CHECKREAD) will
be raised. This error will be treated in the same way as a deadlock:
the transaction will be rolled back.

lock_clust_rec_read_check_and_lock(): If the current transaction has
a read view where the record is not visible and
innodb_snapshot_isolation=ON, fail before trying to acquire the lock.

row_sel_build_committed_vers_for_mysql(): If innodb_snapshot_isolation=ON,
disable the "semi-consistent read" logic that had been implemented by
myself on the directions of Heikki Tuuri in order to address
https://bugs.mysql.com/bug.php?id=3300 that was motivated by a customer
wanting UPDATE to skip locked rows that do not match the WHERE condition.
It looks like my changes were included in the MySQL 5.1.5
commit ad126d90e019f223470e73e1b2b528f9007c4532; at that time, employees
of Innobase Oy (a recent acquisition of Oracle) had lost write access to
the repository.

The only reason why we set innodb_snapshot_isolation=OFF by default is
backward compatibility with applications, such as the one that motivated
the implementation of "semi-consistent read" back in 2005. In a later
major release, we can default to innodb_snapshot_isolation=ON.

Thanks to Peter Alvaro, Kyle Kingsbury and Alexey Gotsman for their work
on https://github.com/jepsen-io/ and to Kyle and Alexey for explanations
and some testing of this fix.

Thanks to Vladislav Lesin for the initial test for MDEV-26643,
as well as reviewing these changes.
2024-03-20 09:48:03 +02:00

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/*****************************************************************************
Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2015, 2022, MariaDB Corporation.
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
*****************************************************************************/
/**************************************************//**
@file include/db0err.h
Global error codes for the database
Created 5/24/1996 Heikki Tuuri
*******************************************************/
#ifndef db0err_h
#define db0err_h
/* Do not include univ.i because univ.i includes this. */
enum dberr_t {
DB_SUCCESS,
DB_SUCCESS_LOCKED_REC= 9, /*!< like DB_SUCCESS, but a new
explicit record lock was created */
/* The following are error codes */
DB_RECORD_CHANGED,
DB_ERROR,
DB_INTERRUPTED,
DB_OUT_OF_MEMORY,
DB_OUT_OF_FILE_SPACE,
DB_LOCK_WAIT,
DB_DEADLOCK,
DB_DUPLICATE_KEY,
DB_MISSING_HISTORY, /*!< required history data has been
deleted due to lack of space in
rollback segment */
#ifdef WITH_WSREP
DB_ROLLBACK,
#endif
DB_TABLE_NOT_FOUND= 31,
DB_TOO_BIG_RECORD, /*!< a record in an index would not fit
on a compressed page, or it would
become bigger than 1/2 free space in
an uncompressed page frame */
DB_LOCK_WAIT_TIMEOUT, /*!< lock wait lasted too long */
DB_NO_REFERENCED_ROW, /*!< referenced key value not found
for a foreign key in an insert or
update of a row */
DB_ROW_IS_REFERENCED, /*!< cannot delete or update a row
because it contains a key value
which is referenced */
DB_CANNOT_ADD_CONSTRAINT, /*!< adding a foreign key constraint
to a table failed */
DB_CORRUPTION, /*!< data structure corruption
noticed */
DB_CANNOT_DROP_CONSTRAINT, /*!< dropping a foreign key constraint
from a table failed */
DB_NO_SAVEPOINT, /*!< no savepoint exists with the given
name */
DB_TABLESPACE_EXISTS, /*!< we cannot create a new single-table
tablespace because a file of the same
name already exists */
DB_TABLESPACE_DELETED, /*!< tablespace was deleted or is
being dropped right now */
DB_TABLESPACE_NOT_FOUND, /*<! Attempt to delete a tablespace
instance that was not found in the
tablespace hash table */
DB_LOCK_TABLE_FULL, /*!< lock structs have exhausted the
buffer pool (for big transactions,
InnoDB stores the lock structs in the
buffer pool) */
DB_FOREIGN_DUPLICATE_KEY, /*!< foreign key constraints
activated by the operation would
lead to a duplicate key in some
table */
DB_TOO_MANY_CONCURRENT_TRXS, /*!< when InnoDB runs out of the
preconfigured undo slots, this can
only happen when there are too many
concurrent transactions */
DB_UNSUPPORTED, /*!< when InnoDB sees any artefact or
a feature that it can't recoginize or
work with e.g., FT indexes created by
a later version of the engine. */
DB_INVALID_NULL, /*!< a NOT NULL column was found to
be NULL during table rebuild */
DB_STATS_DO_NOT_EXIST, /*!< an operation that requires the
persistent storage, used for recording
table and index statistics, was
requested but this storage does not
exist itself or the stats for a given
table do not exist */
DB_FOREIGN_EXCEED_MAX_CASCADE, /*!< Foreign key constraint related
cascading delete/update exceeds
maximum allowed depth */
DB_CHILD_NO_INDEX, /*!< the child (foreign) table does
not have an index that contains the
foreign keys as its prefix columns */
DB_PARENT_NO_INDEX, /*!< the parent table does not
have an index that contains the
foreign keys as its prefix columns */
DB_TOO_BIG_INDEX_COL, /*!< index column size exceeds
maximum limit */
DB_INDEX_CORRUPT, /*!< we have corrupted index */
DB_UNDO_RECORD_TOO_BIG, /*!< the undo log record is too big */
DB_READ_ONLY, /*!< Update operation attempted in
a read-only transaction */
DB_FTS_INVALID_DOCID, /* FTS Doc ID cannot be zero */
DB_ONLINE_LOG_TOO_BIG, /*!< Modification log grew too big
during online index creation */
DB_IDENTIFIER_TOO_LONG, /*!< Identifier name too long */
DB_FTS_EXCEED_RESULT_CACHE_LIMIT, /*!< FTS query memory
exceeds result cache limit */
DB_TEMP_FILE_WRITE_FAIL, /*!< Temp file write failure */
DB_CANT_CREATE_GEOMETRY_OBJECT, /*!< Cannot create specified Geometry
data object */
DB_CANNOT_OPEN_FILE, /*!< Cannot open a file */
DB_FTS_TOO_MANY_WORDS_IN_PHRASE,
/*< Too many words in a phrase */
DB_DECRYPTION_FAILED, /* Tablespace encrypted and
decrypt operation failed because
of missing key management plugin,
or missing or incorrect key or
incorret AES method or algorithm. */
DB_IO_ERROR = 100, /*!< Generic IO error */
DB_IO_PARTIAL_FAILED, /*!< Partial IO request failed */
DB_TABLE_CORRUPT, /*!< Table/clustered index is
corrupted */
DB_COMPUTE_VALUE_FAILED, /*!< Compute generated value failed */
DB_NO_FK_ON_S_BASE_COL, /*!< Cannot add foreign constrain
placed on the base column of
stored column */
DB_IO_NO_PUNCH_HOLE, /*!< Punch hole not supported by
file system. */
DB_PAGE_CORRUPTED, /* Page read from tablespace is
corrupted. */
/* The following are partial failure codes */
DB_FAIL = 1000,
DB_OVERFLOW,
DB_UNDERFLOW,
DB_STRONG_FAIL,
DB_ZIP_OVERFLOW,
DB_RECORD_NOT_FOUND = 1500,
DB_END_OF_INDEX,
DB_NOT_FOUND, /*!< Generic error code for "Not found"
type of errors */
};
#endif
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