Issue Number: close#31569
Fix fe connection hang after too high qps
After fix, the third SQL will return error instead of hang:
ERROR 1203 (HY000): #42000Too many connections
* Test the unique model by modify a value type from BOOLEAN to other type
* Test the unique model by modify a key type from BOOLEAN to other type
* Test the unique model by modify a key type from BOOLEAN to other type
It supports predicate composite as following:
materialized view define
> select l_shipdate, o_orderdate, l_partkey, l_suppkey
> from lineitem_1
> left join orders_1
> on lineitem_1.l_orderkey = orders_1.o_orderkey
> where l_shipdate > '2023-10-19'
the query as following can be rewritten by the materialized view above
> select l_shipdate, o_orderdate, l_partkey, l_suppkey
> from lineitem_1
> left join orders_1
> on lineitem_1.l_orderkey = orders_1.o_orderkey
> where l_shipdate > '2023-10-25'
When left join with no edge in outer side, we should add outer side to minimal require of left tables
Co-authored-by: libinfeng <libinfeng@selectdb.com>
When compaction, if some segments miss variant root, there is chance to get emtpy root variant.So add some defence
code in OlapColumnDataConvertorVariant to prevent from accessing null root
```
5# doris::vectorized::ColumnObject::Subcolumn::get_finalized_column_ptr() const at /mnt/ssd01/selectdb-doris-package/enterprise-core/be/src/vec/columns/column_object.cpp:556
6# doris::vectorized::OlapBlockDataConvertor::OlapColumnDataConvertorVariant::set_source_column(doris::vectorized::ColumnWithTypeAndName const&, unsigned long, unsigned long) at /mnt/ssd01/selectdb-doris-package/enterprise-core/be/src
/vec/olap/olap_data_convertor.cpp:1076
7# doris::vectorized::OlapBlockDataConvertor::set_source_content(doris::vectorized::Block const*, unsigned long, unsigned long) at /mnt/ssd01/selectdb-doris-package/enterprise-core/be/src/vec/olap/olap_data_convertor.cpp:207
8# doris::segment_v2::SegmentWriter::append_block(doris::vectorized::Block const*, unsigned long, unsigned long) at /mnt/ssd01/selectdb-doris-package/enterprise-core/be/src/olap/rowset/segment_v2/segment_writer.cpp:727
9# doris::VerticalBetaRowsetWriter::add_columns(doris::vectorized::Block const*, std::vector > const&, bool, unsigned int) at /mnt/ssd01/selectdb-doris-package/enterprise-core/be/src/olap/row
set/vertical_beta_rowset_writer.cpp:125
```
