If you manage to shut down PrimProc just before plugin is trying to send
Calpont Select Execution Plan to PrimProc, you now get a nice error
message about PrimProc being down instead of endless logs of failed
reconnection attempts.
There were numerous memory leaks in plugin's code and associated code.
During typical run of MTR tests it leaked around 65 megabytes of
objects. As a result they may severely affect long-lived connections.
This patch fixes (almost) all leaks found in the plugin. The exceptions
are two leaks associated with SHOW CREATE TABLE columnstore_table and
getting information of columns of columnstore-handled table. These
should be fixed on the server side and work is on the way.
For UPDATEs involving a single table, the server call to handler::direct_update_rows() is used to correctly set the count for the number of updated rows in the UPDATE statement.
However, for UPDATEs involving multi-tables, the server does not call handler::direct_update_rows(). This patch adds support to correctly report the number of updated rows to the client by setting
multi_update::updated and multi_update::found in handler::rnd_end().
This patch improves handling of NULLs in textual fields in ColumnStore.
Previously empty strings were considered NULLs and it could be a problem
if data scheme allows for empty strings. It was also one of major
reasons of behavior difference between ColumnStore and other engines in
MariaDB family.
Also, this patch fixes some other bugs and incorrect behavior, for
example, incorrect comparison for "column <= ''" which evaluates to
constant True for all purposes before this patch.
Analyze needs to be completed differently than a normal query. In server, when an ANALYZE is seen, it calls init_scan() immediatly followed by end_scan(). This leaves the sqlfrontendsession (ExeMgr) in a state where it expects to return rows. This patch fixes end_scan to clean this up via reads and writes to get everything back in synch.
ANALYZE should display the number of rows to be displayed if the query were run normally. We have that information available, but no way to return it. A modification to server side to ask for that in the handler is required.
This patch also includes a beautification of sqlfrontsessionthread.cpp since it looked bad. The important change is at line 774
if (!swallowRows)
which short circuits the actual return of data
Exit early from the plugin execution of ALTER TABLE statements
on the replica nodes. This is to prevent re-execution of syscat
table population from the replica nodes which should only be
executed once by the primary node in a CS cluster setup.
Part 1:
As part of MCOL-3776 to address synchronization issue while accessing
the fTimeZone member of the Func class, mutex locks were added to the
accessor and mutator methods. However, this slows down processing
of TIMESTAMP columns in PrimProc significantly as all threads across
all concurrently running queries would serialize on the mutex. This
is because PrimProc only has a single global object for the functor
class (class derived from Func in utils/funcexp/functor.h) for a given
function name. To fix this problem:
(1) We remove the fTimeZone as a member of the Func derived classes
(hence removing the mutexes) and instead use the fOperationType
member of the FunctionColumn class to propagate the timezone values
down to the individual functor processing functions such as
FunctionColumn::getStrVal(), FunctionColumn::getIntVal(), etc.
(2) To achieve (1), a timezone member is added to the
execplan::CalpontSystemCatalog::ColType class.
Part 2:
Several functors in the Funcexp code call dataconvert::gmtSecToMySQLTime()
and dataconvert::mySQLTimeToGmtSec() functions for conversion between seconds
since unix epoch and broken-down representation. These functions in turn call
the C library function localtime_r() which currently has a known bug of holding
a global lock via a call to __tz_convert. This significantly reduces performance
in multi-threaded applications where multiple threads concurrently call
localtime_r(). More details on the bug:
https://sourceware.org/bugzilla/show_bug.cgi?id=16145
This bug in localtime_r() caused processing of the Functors in PrimProc to
slowdown significantly since a query execution causes Functors code to be
processed in a multi-threaded manner.
As a fix, we remove the calls to localtime_r() from gmtSecToMySQLTime()
and mySQLTimeToGmtSec() by performing the timezone-to-offset conversion
(done in dataconvert::timeZoneToOffset()) during the execution plan
creation in the plugin. Note that localtime_r() is only called when the
time_zone system variable is set to "SYSTEM".
This fix also required changing the timezone type from a std::string to
a long across the system.
DML statements executed on the primary node in a ColumnStore
cluster do not need to be written to the primary's binlog. This
is due to ColumnStore's distributed storage architecture.
With this patch, we disable writing to binlog when a DML statement
(INSERT/DELETE/UPDATE/LDI/INSERT..SELECT) is performed on a ColumnStore
table. HANDLER::external_lock() calls are used to
1. Turn OFF the OPTION_BIN_LOG flag
2. Turn ON the OPTION_BIN_TMP_LOG_OFF flag
in THD::variables.option_bits during a WRITE lock call.
THD::variables.option_bits is restored back to the original state
during the UNLOCK call in HANDLER::external_lock().
Further, isDMLStatement() function is added to reduce code verbosity
to check if a given statement is a DML statement.
Note that with this patch, not writing to primary's binlog means
DML replication from a ColumnStore cluster to another ColumnStore
cluster or to another foreign engine will not work.
on a non-ColumnStore table does not work.
As part of MCOL-4617, we moved the in-to-exists predicate creation
and injection from the server into the engine. However, when query
with an IN Subquery contains a non-ColumnStore table, the server
still performs the in-to-exists predicate transformation for the
foreign engine table. This caused ColumnStore's execution plan to
contain incorrect WHERE predicates. As a fix, we call
mutate_optimizer_flags() for the WRITE lock, in addition to the READ
table lock. And in mutate_optimizer_flags(), we change the optimizer
flag from OPTIMIZER_SWITCH_IN_TO_EXISTS to OPTIMIZER_SWITCH_MATERIALIZATION.
1. Add a new system variable, columnstore_use_cpimport_for_cache_inserts,
that when set to ON, uses cpimport for the cache flush into ColumnStore.
This variable is set to OFF by default. By default, we perform batch inserts
for the cache flush.
2. Disable DMLProc logging of the SQL statement text for the cache
flush operation in case of batch inserts. Under certain heavy loads
involving INSERT statements, this logging becomes a bottleneck for
the cache flush, causing subsequent inserts into the cache table to hang.
cross-engine join with a ColumnStore table errors out.
ColumnStore cannot directly update a foreign table. We detect whether
a multi-table UPDATE operation is performed on a foreign table, if so,
do not create the select_handler and let the server execute the UPDATE
operation instead.
This feature allows a query execution to fallback to the server,
in case query execution using the select_handler (SH) fails. In case
of fallback, a warning message containing the original reason for
query failure using SH is generated.
To accomplish this task, SH execution is moved to an earlier step when
we create the SH in create_columnstore_select_handler(), instead of the
previous call to SH execution in ha_columnstore_select_handler::init_scan().
This requires some pre-requisite steps that occur in the server in
JOIN::optimize() and JOIN::exec() to be performed before starting SH execution.
In addition, missing test cases from MCOL-424 are also added to the MTR suite,
and the corresponding fix using disable_indices_for_CEJ() is reverted back
since the original fix now appears to be redundant.
This is a subtask of MCOL-4525 Implement select_handler=AUTO.
Server performs outer join to inner join conversion using simplify_joins()
in sql/sql_select.cc, by updating the TABLE_LIST::outer_join variable.
In order to perform this conversion, permanent changes are made in some
cases to the SELECT_LEX::JOIN::conds and/or TABLE_LIST::on_expr.
This is undesirable for MCOL-4525 which will attemp to fallback and execute
the query inside the server, in case the query execution fails in ColumnStore
using the select_handler.
For a query such as:
SELECT * FROM t1 LEFT JOIN t2 ON expr1 LEFT JOIN t3 ON expr2
In some cases, server can update the original SELECT_LEX::JOIN::conds
and/or TABLE_LIST::on_expr and create new Item_cond_and objects
(e.g. with 2 Item's expr1 and expr2 in Item_cond_and::list).
Instead of making changes to the original query structs, we use
gp_walk_info::tableOnExprList and gp_walk_info::condList. 2 Item's,
expr1 and expr2, in the condList, mean Item_cond_and(expr1, expr2), and
hence avoid permanent transformations to the SELECT_LEX.
We also define a new member variable
ha_columnstore_select_handler::tableOuterJoinMap
which saves the original TABLE_LIST::outer_join values before they are
updated. This member variable will be used later on to restore to the original
state of TABLE_LIST::outer_join in case of a query fallback to server execution.
The original simplify_joins() implementation in the server also performs a
flattening of the JOIN nest, however we don't perform this operation in
convertOuterJoinToInnerJoin() since it is not required for ColumnStore.
mcsconfig.h and my_config.h have the following
pre-processor definitions:
1. Conflicting definitions coming from the standard cmake definitions:
- PACKAGE
- PACKAGE_BUGREPORT
- PACKAGE_NAME
- PACKAGE_STRING
- PACKAGE_TARNAME
- PACKAGE_VERSION
- VERSION
2. Conflicting definitions of other kinds:
- HAVE_STRTOLL - this is a dirt in MariaDB headers.
Should be fixed in the server code. my_config.h erroneously
performs "#define HAVE_STRTOLL" instead of "#define HAVE_STRTOLL 1".
in some cases. The former is not CMake compatible style. The latter is.
3. Non-conflicting definitions:
Otherwise, mcsconfig.h and my_config.h should be mutually compatible,
because both are generated by cmake on the same host machine. So
they should have exactly equal definitions like "HAVE_XXX", "SIZEOF_XXX", etc.
Observations:
- It's OK to include both mcsconfig.h and my_config.h providing that we
suppress duplicate definition of the above conflicting types #1 and #2.
- There is no a need to suppress duplicate definitions mentioned in #3,
as they are compatible!
- my_sys.h and m_ctype.h must always follow a CMake configuation header,
either my_config.h or mcsconfig.h (or both).
They must never be included without any preceeding configuration header.
This change make sure that we resolve conflicts by:
- either disallowing inclusion of mcsconfig.h and my_config.h
at the same time
- or by hiding conflicting definitions #1 and #2
(with their later restoring).
- also, by making sure that my_sys.h and m_ctype.h always follow
a CMake configuration file.
Details:
- idb_mysql.h can now only be included only after my_config.h
An attempt to use idb_mysql.h with mcsconfig.h instead of
my_config.h is caught by the "#error" preprocessor directive.
- mariadb_my_sys.h can now be only included after mcsconfig.h.
An attempt to use mariadb_my_sys.h without mcscofig.h
(e.g. with my_config.h) is also caught by "#error".
- collation.h now can now be included in two ways.
It now has the following effective structure:
#if defined(PREFER_MY_CONFIG_H) && defined(MY_CONFIG_H)
// Remember current conflicting definitions on the preprocessor stack
// Undefine current conflicting definitions
#endif
#include "mcsconfig.h"
#include "m_ctype.h"
#if defined(PREFER_MY_CONFIG_H) && defined(MY_CONFIG_H)
# Restore conflicting definitions from the preprocessor stack
#endif
and can be included as follows:
a. using only mcsconfig.h as a configuration header:
// my_config.h must not be included so far
#include "collation.h"
b. using my_config.h as the first included configuration file:
#define PREFER_MY_CONFIG_H // Force conflict resolution
#include "my_config.h" // can be included directly or indirectly
...
#include "collation.h"
Other changes:
- Adding helper header files
utils/common/mcsconfig_conflicting_defs_remember.h
utils/common/mcsconfig_conflicting_defs_restore.h
utils/common/mcsconfig_conflicting_defs_undef.h
to perform conflict resolution easier.
- Removing `#include "collation.h"` from a number of files,
as it's automatically included from rowgroup.h.
- Removing redundant `#include "utils_utf8.h"`.
This change is not directly related to the problem being fixed,
but it's nice to remove redundant directives for both collation.h
and utils_utf8.h from all the files that do not really need them.
(this change could probably have gone as a separate commit)
- Changing my_init() to MY_INIT(argv[0]) in the MCS services sources.
After the fix of the complitation failure it appeared that ColumnStore
services compiled with the debug build crash due to recent changes in
safemalloc. The crash happened in strcmp() with `my_progname` as an argument
(where my_progname is a mysys global variable). This problem should
probably be fixed on the server side as well to avoid passing NULL.
But, the majority of MariaDB executable programs also use MY_INIT(argv[0])
rather than my_init(). So let's make MCS do like the other programs do.
An INSERT .. SELECT performed on a master node caused an infinite
loop on the slave node with columnstore_replication_slave=OFF.
The issue was ha_mcs_impl_select_next() was returning 0 if
the executing thread is a slave and returning early to avoid DML
execution on the slave. The calling code in select_handler::execute()
ran into an infinite loop due to this as it checked the return code
of the function as 0, and incorrectly thought there are more rows
to process.
The fix is to return HA_ERR_END_OF_FILE as the return value,
instead of 0. This is for the case of the query running on the
slave node with columnstore_replication_slave=OFF.
For now it consists of only:
using int128_t = __int128;
using uint128_t = unsigned __int128;
All new privitive data types should go into this file in the future.
2. Set Decimal precision in SimpleColumn::evaluate().
3. Add support for int128_t in ConstantColumn.
4. Set IDB_Decimal::s128Value in buildDecimalColumn().
5. Use width 16 as first if predicate for branching based on decimal width.
