This is part of the array type support and has not been fully completed.
The following functions are implemented
1. fe array type support and implementation of array function, support array syntax analysis and planning
2. Support import array type data through insert into
3. Support select array type data
4. Only the array type is supported on the value lie of the duplicate table
this pr merge some code from #4655#4650#4644#4643#4623#2979
fix a bug of const union query like `select null union select null`, this because the type of SlotDescriptor when clause is `select null` is null ,this will cause BE core dump, and FE find wrong cast function.
Add a new type: Object. Currently, it's mainly for complex aggregate metrics(HLL , Bitmap).
The Object type has the following constraints:
1 Object type could not as key column type
2 Object type doesn't support all indices (BloomFilter, short key, zone map, invert index)
3 Object type doesn't support filter and group by
In the implementation:
The Object type reuse the StringValue and StringVal, because in storage engine, the Object type is binary, it has a pointer and length.