bug: Insert a space，SELECT COUNT(DISTINCT col2) FROM t1;Error query result

[shangyanwen]

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• I have read the Contributing Guidelines on issues.

Please confirm if bug report does NOT exists already ?

• I confirm there is no existing issue for this

Describe the problem

CREATE TABLE t1(col1 INT, col2 CHAR(5))ENGINE=tianmu;
INSERT INTO t1 VALUES(NULL,''),(1,'a'),(1,'b'),(1,'c'),(2,'dd'),(3,'eee');
SELECT COUNT(DISTINCT col2) FROM t1;

##The error results are as follows
+----------------------+
| COUNT(DISTINCT col2) |
+----------------------+
|                    1 |
+----------------------+

Expected behavior

##The following is：innodb test result,mariadb-Columnstore test result is 5

mysql> SELECT COUNT(DISTINCT col2) FROM t1;
+----------------------+
| COUNT(DISTINCT col2) |
+----------------------+
|                    6 
+----------------------+

How To Reproduce

CREATE TABLE t1(col1 INT, col2 CHAR(5))ENGINE=tianmu;
INSERT INTO t1 VALUES(NULL,''),(1,'a'),(1,'b'),(1,'c'),(2,'dd'),(3,'eee');
SELECT COUNT(DISTINCT col2) FROM t1;

### Environment

Ver 14.14 Distrib 5.7.36-StoneDB

### Are you interested in submitting a PR to solve the problem?

- [ ] Yes, I will!

[shangyanwen]

###Insert data without space, the test result is correct
SELECT COUNT(DISTINCT col1) FROM t1;

[lylth]

The stack for setting the count value is as follows:

Tianmu::core::AggregatorCount32::PutAggregatedValue(Tianmu::core::AggregatorCount32 * const this, unsigned char * buf, int64_t factor) (\opt\litaihong\stonedb\storage\tianmu\core\aggregator.h:300)
Tianmu::core::AggregatorCount32::PutAggregatedValue(Tianmu::core::AggregatorCount32 * const this, unsigned char * buf, const Tianmu::types::BString & v, int64_t factor) (\opt\litaihong\stonedb\storage\tianmu\core\aggregator.h:313)
Tianmu::core::GroupTable::PutAggregatedValue(Tianmu::core::GroupTable * const this, int col, int64_t row, Tianmu::core::MIIterator & mit, int64_t factor, bool as_string) (\opt\litaihong\stonedb\storage\tianmu\core\group_table.cpp:556)
Tianmu::core::GroupByWrapper::PutAggregatedValue(Tianmu::core::GroupByWrapper * const this, int gr_a, int64_t pos, Tianmu::core::MIIterator & mit, int64_t factor) (\opt\litaihong\stonedb\storage\tianmu\core\groupby_wrapper.cpp:509)
Tianmu::core::AggregationAlgorithm::AggregatePackrow(Tianmu::core::AggregationAlgorithm * const this, Tianmu::core::GroupByWrapper & gbw, Tianmu::core::MIIterator * mit, int64_t cur_tuple) (\opt\litaihong\stonedb\storage\tianmu\core\aggregation_algorithm.cpp:591)
Tianmu::core::AggregationAlgorithm::MultiDimensionalGroupByScan(Tianmu::core::AggregationAlgorithm * const this, Tianmu::core::GroupByWrapper & gbw, int64_t & limit, int64_t & offset, Tianmu::core::ResultSender * sender, bool limit_less_than_no_groups, bool force_parall) (\opt\litaihong\stonedb\storage\tianmu\core\aggregation_algorithm.cpp:292)
Tianmu::core::AggregationAlgorithm::Aggregate(Tianmu::core::AggregationAlgorithm * const this, bool just_distinct, int64_t & limit, int64_t & offset, Tianmu::core::ResultSender * sender) (\opt\litaihong\stonedb\storage\tianmu\core\aggregation_algorithm.cpp:197)
Tianmu::core::TempTable::Materialize(Tianmu::core::TempTable * const this, bool in_subq, Tianmu::core::ResultSender * sender, bool lazy) (\opt\litaihong\stonedb\storage\tianmu\core\temp_table.cpp:1972)
Tianmu::core::Engine::Execute(Tianmu::core::Engine * const this, THD * thd, LEX * lex, Query_result * result_output, SELECT_LEX_UNIT * unit_for_union) (\opt\litaihong\stonedb\storage\tianmu\core\engine_execute.cpp:426)
Tianmu::core::Engine::HandleSelect(Tianmu::core::Engine * const this, THD * thd, LEX * lex, Query_result *& result, ulong setup_tables_done_option, int & res, int & optimize_after_tianmu, int & tianmu_free_join, int with_insert) (\opt\litaihong\stonedb\storage\tianmu\core\engine_execute.cpp:232)
Tianmu::dbhandler::TIANMU_HandleSelect(THD * thd, LEX * lex, Query_result *& result, ulong setup_tables_done_option, int & res, int & optimize_after_tianmu, int & tianmu_free_join, int with_insert) (\opt\litaihong\stonedb\storage\tianmu\handler\ha_rcengine.cpp:82)
execute_sqlcom_select(THD * thd, TABLE_LIST * all_tables) (\opt\litaihong\stonedb\sql\sql_parse.cc:5182)
mysql_execute_command(THD * thd, bool first_level) (\opt\litaihong\stonedb\sql\sql_parse.cc:2831)
mysql_parse(THD * thd, Parser_state * parser_state) (\opt\litaihong\stonedb\sql\sql_parse.cc:5621)
dispatch_command(THD * thd, const COM_DATA * com_data, enum_server_command command) (\opt\litaihong\stonedb\sql\sql_parse.cc:1495)
do_command(THD * thd) (\opt\litaihong\stonedb\sql\sql_parse.cc:1034)
handle_connection(void * arg) (\opt\litaihong\stonedb\sql\conn_handler\connection_handler_per_thread.cc:313)
pfs_spawn_thread(void * arg) (\opt\litaihong\stonedb\storage\perfschema\pfs.cc:2197)
libpthread.so.0!start_thread (未知源:0)
libc.so.6!clone (未知源:0)

The FindCurrentRow function returns GBIMODE_AS_TEXT to enter the accumulation process, and the FindCurrentRowByVMTable function returns GDT_EXISTS to enter the re-counting process, resulting in the string type of count being always 1.

Tianmu::core::GroupDistinctTable::FindCurrentRow(Tianmu::core::GroupDistinctTable * const this, bool find_only) (\opt\litaihong\stonedb\storage\tianmu\core\group_distinct_table.cpp:282)
Tianmu::core::GroupDistinctTable::Add(Tianmu::core::GroupDistinctTable * const this, int64_t group, Tianmu::core::MIIterator & mit) (\opt\litaihong\stonedb\storage\tianmu\core\group_distinct_table.cpp:179)
Tianmu::core::GroupTable::PutAggregatedValue(Tianmu::core::GroupTable * const this, int col, int64_t row, Tianmu::core::MIIterator & mit, int64_t factor, bool as_string) (\opt\litaihong\stonedb\storage\tianmu\core\group_table.cpp:538)
Tianmu::core::GroupByWrapper::PutAggregatedValue(Tianmu::core::GroupByWrapper * const this, int gr_a, int64_t pos, Tianmu::core::MIIterator & mit, int64_t factor) (\opt\litaihong\stonedb\storage\tianmu\core\groupby_wrapper.cpp:509)
Tianmu::core::AggregationAlgorithm::AggregatePackrow(Tianmu::core::AggregationAlgorithm * const this, Tianmu::core::GroupByWrapper & gbw, Tianmu::core::MIIterator * mit, int64_t cur_tuple) (\opt\litaihong\stonedb\storage\tianmu\core\aggregation_algorithm.cpp:591)
Tianmu::core::AggregationAlgorithm::MultiDimensionalGroupByScan(Tianmu::core::AggregationAlgorithm * const this, Tianmu::core::GroupByWrapper & gbw, int64_t & limit, int64_t & offset, Tianmu::core::ResultSender * sender, bool limit_less_than_no_groups, bool force_parall) (\opt\litaihong\stonedb\storage\tianmu\core\aggregation_algorithm.cpp:292)
Tianmu::core::AggregationAlgorithm::Aggregate(Tianmu::core::AggregationAlgorithm * const this, bool just_distinct, int64_t & limit, int64_t & offset, Tianmu::core::ResultSender * sender) (\opt\litaihong\stonedb\storage\tianmu\core\aggregation_algorithm.cpp:197)
Tianmu::core::TempTable::Materialize(Tianmu::core::TempTable * const this, bool in_subq, Tianmu::core::ResultSender * sender, bool lazy) (\opt\litaihong\stonedb\storage\tianmu\core\temp_table.cpp:1972)
Tianmu::core::Engine::Execute(Tianmu::core::Engine * const this, THD * thd, LEX * lex, Query_result * result_output, SELECT_LEX_UNIT * unit_for_union) (\opt\litaihong\stonedb\storage\tianmu\core\engine_execute.cpp:426)
Tianmu::core::Engine::HandleSelect(Tianmu::core::Engine * const this, THD * thd, LEX * lex, Query_result *& result, ulong setup_tables_done_option, int & res, int & optimize_after_tianmu, int & tianmu_free_join, int with_insert) (\opt\litaihong\stonedb\storage\tianmu\core\engine_execute.cpp:232)
Tianmu::dbhandler::TIANMU_HandleSelect(THD * thd, LEX * lex, Query_result *& result, ulong setup_tables_done_option, int & res, int & optimize_after_tianmu, int & tianmu_free_join, int with_insert) (\opt\litaihong\stonedb\storage\tianmu\handler\ha_rcengine.cpp:82)
execute_sqlcom_select(THD * thd, TABLE_LIST * all_tables) (\opt\litaihong\stonedb\sql\sql_parse.cc:5182)
mysql_execute_command(THD * thd, bool first_level) (\opt\litaihong\stonedb\sql\sql_parse.cc:2831)
mysql_parse(THD * thd, Parser_state * parser_state) (\opt\litaihong\stonedb\sql\sql_parse.cc:5621)
dispatch_command(THD * thd, const COM_DATA * com_data, enum_server_command command) (\opt\litaihong\stonedb\sql\sql_parse.cc:1495)
do_command(THD * thd) (\opt\litaihong\stonedb\sql\sql_parse.cc:1034)
handle_connection(void * arg) (\opt\litaihong\stonedb\sql\conn_handler\connection_handler_per_thread.cc:313)
pfs_spawn_thread(void * arg) (\opt\litaihong\stonedb\storage\perfschema\pfs.cc:2197)
libpthread.so.0!start_thread (未知源:0)
libc.so.6!clone (未知源:0)

[lylth]

The AggregatePackrow function call flow is as follows：

AggregationAlgorithm::AggregatePackrow
--------------------------->AggregateRough--->FindCurrentRow--->GroupTable::FindCurrentRow--->FindCurrentRow
--------------------------------------------------------------------------------------------->GetAggregationRow
--------------------------------------------->AddGroup
--------------------------------------------->InvalidateAggregationStatistics
--------------------------------------------->PackWillNotUpdateAggregation
--------------------------->GroupByWrapper::PutAggregatedValue--->GroupTable::PutAggregatedValue--->GroupDistinctTable::Add--->ColumnBinEncoder::ValEncode--->ColumnBinEncoder::EncoderInt::ValEncode--->GetNotNullValueInt64--->GetNotNullValueInt64
------------------------------------------------------------------------------------------------------------------------------>FindCurrentRowByVMTable
--------------------------------------------------------------------------------------------------->PutAggregatedValue
--------------------------->GroupByWrapper::PutAggregatedValue--->GroupTable::PutAggregatedValue