1. Before this PR if rowset does not contain column which should be read for related SlotDescriptor will call `insert_default` to column, but it's not this real defautl value.Real default value relevant information should be provided by the frontend side.
2. Support fetch when light schema change is not enabled, but disable for AGG or UNIQUE MOR model
1. Get DataTypeSerde in advance to avoid get temporary DataTypeSerde iterate each column
2. Iterate the original row once is enoungh for deserializing by introducing a map for record the index of each column's unique id
Currently, there are some useless includes in the codebase. We can use a tool named include-what-you-use to optimize these includes. By using a strict include-what-you-use policy, we can get lots of benefits from it.
This PR optimize topn query like `SELECT * FROM tableX ORDER BY columnA ASC/DESC LIMIT N`.
TopN is is compose of SortNode and ScanNode, when user table is wide like 100+ columns the order by clause is just a few columns.But ScanNode need to scan all data from storage engine even if the limit is very small.This may lead to lots of read amplification.So In this PR I devide TopN query into two phase:
1. The first phase we just need to read `columnA`'s data from storage engine along with an extra RowId column called `__DORIS_ROWID_COL__`.The other columns are pruned from ScanNode.
2. The second phase I put it in the ExchangeNode beacuase it's the central node for topn nodes in the cluster.The ExchangeNode will spawn a RPC to other nodes using the RowIds(sorted and limited from SortNode) read from the first phase and read row by row from storage engine.
After the second phase read, Block will contain all the data needed for the query
