Now column `Array<T>` contains column `offsets` and `data`, and type of column `offsets` is UInt32 now.
If we call array_union to merge arrays repeatedly, the size of array may overflow.
So we need to extend it before `Array Data Type` release.
## Design:
For now, there are two categories of types in Doris, one is for scalar types (such as int, char and etc.) and the other is for composite types (array and etc.). For the sake of performance, we can cache type info of scalar types globally (unique objects) due to the limited number of scalar types. When we consider the composite types, normally, the type info is generated in runtime (we can also use some cache strategy to speed up). The memory thereby should be reclaimed when we create type info for composite types.
There are a lots of interfaces to get the type info of a specific type. I reorganized those as the following describes.
1. `const TypeInfo* get_scalar_type_info(FieldType field_type)`
The function is used to get the type info of scalar types. Due to the cache, the caller uses the result **WITHOUT** considering the problems about memory reclaim.
2. `const TypeInfo* get_collection_type_info(FieldType sub_type)`
The function is used to get the type info of array types with just **ONE** depth. Due to the cache, the caller uses the result **WITHOUT** considering the problems about memory reclaim.
3. `TypeInfoPtr get_type_info(segment_v2::ColumnMetaPB* column_meta_pb)`
4. `TypeInfoPtr get_type_info(const TabletColumn* col)`
These functions are used to get the type info of **BOTH** scalar types and composite types. The caller should be responsible to manage the resources returned.
#### About the new type `TypeInfoPtr`
`TypeInfoPtr` is an alias type to `unique_ptr` with a custom deleter.
1. For scalar types, the deleter does nothing.
2. For composite types, the deleter reclaim the memory.
By analyzing the callers of `get_type_info`, these classes should hold TypeInfoPtr:
1. `Field`
2. `ColumnReader`
3. `DefaultValueColumnIterator`
Other classes are either constructed by the foregoing classes or hold those, so they can just use the raw pointer of `TypeInfo` directly for the sake of performance.
1. `ScalarColumnWriter` - holds `Field`
1. `ZoneMapIndexWriter` - created by `ScalarColumnWriter`, use `type_info` from the field in `ScalarColumnWriter`
1. `IndexedColumnWriter` - created by `ZoneMapIndexWriter`, only uses scalar types.
2. `BitmapIndexWriter` - created by `ScalarColumnWriter`, uses `type_info` from the field in `ScalarColumnWriter`
1. `IndexedColumnWriter` - created by `BitmapIndexWriter`, uses `type_info` in `BitmapIndexWriter` and `BitmapIndexWriter` doesn't support `ArrayType`.
3. `BloomFilterIndexWriter` - created by `ScalarColumnWriter`, uses `type_info` from the field in `ScalarColumnWriter`
1. `IndexedColumnWriter` - created by `BloomFilterIndexWriter`, only uses scalar types.
2. `IndexedColumnReader` initializes `type_info` by the field type in meta (only scalar types).
3. `ColumnVectorBatch`
1. `ZoneMapIndexReader` creates `ColumnVectorBatch`, `ColumnVectorBatch` uses `type_info` in `IndexedColumnReader`
2. `BitmapIndexReader` supports scalar types only and it creates `ColumnVectorBatch`, `ColumnVectorBatch` uses `type_info` in `BitmapIndexReader`
3. `BloomFilterIndexWriter` supports scalar types only and it creates `ColumnVectorBatch`, `ColumnVectorBatch` uses `type_info` in `BloomFilterIndexWriter`
Add a new column-type to speed up the approximation of quantiles.
1. The new column-type is named `quantile_state` with fixed aggregation function `quantile_union`, which stores the intermediate results of pre-aggregated approximation calculations for quantiles.
2. support pre-aggregation of new column-type and quantile_state related functions.
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
This CL includes:
* Change the column metadata to a tree structure.
* Refactor the segment_v2.ColumnReader and sgment_v2.ColumnWriter to support complex type.
* Implements the reading and writing of array type.
