vagetablechicken edited a comment on issue #3469:
URL:
https://github.com/apache/incubator-doris/issues/3469#issuecomment-639358916
### Prepare Phase Detail Design
#### Sender BE:
```
Get batch from json_scanner
For partialrow in batch:
// If missing key cols, returns error. Otherwise returns ok.
// If we want to support default values(only for non-key cols) for each
write txn,
// those default values need to be pass to receiver BE
// (e.g. PTabletWriterOpenRequest adds a field). And no need to
// modify rows here, coz we only need key cols here. Filling non-key
cols
// could exec in commit phase.
RETURN_IF_ERROR(calc_partition_and_tablet(partialrow, &channel,
&tablet_id))
channel.add_row(partialrow, tablet_id)
```
#### Receiver BE:
```
Get batch from sender BE
For partialrow, tablet_id of batch:
get delta_writer by tablet_id
delta_writer.write(partialrow)
```
##### DeltaWriter(DeltaWriter has two mode, one for disk engine, one for
memory engine. Sets up the mode upon initialization)
```
// change arg Tuple* to void*
// disk engine MemTable will convert it to Tuple
// memory engine MemTable will convert it to PartialRow
DeltaWriter::insert(void* row):
mem_table.insert(row)
if memory_usage > config:
_flush_memtable_async()
_reset_mem_table()
```
##### WTDMemTable(WriteTxnData MemTable, flush WriteTxnData files)
Member var: _buffer, ...
```
WTDMemTable::insert(void* row):
append(_buffer, row, sizeof(uint32_t)+*(uint32_t*)row)
num_rows++;
WTDMemTable::flush():
// footer will save the default values of non-key cols in schema
part(ColumnMetaPB).
// Use the default values for this write txn, otherwise use the default
values
// in tablet schema.
append(_buffer, footer)
write_to_disk(_buffer)
```
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