mqliang commented on a change in pull request #6710:
URL: https://github.com/apache/incubator-pinot/pull/6710#discussion_r599306832
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File path:
pinot-core/src/main/java/org/apache/pinot/core/common/datatable/DataTableImplV2V3.java
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@@ -33,12 +33,15 @@
import org.apache.pinot.common.utils.DataTable;
import org.apache.pinot.common.utils.StringUtil;
import org.apache.pinot.core.common.ObjectSerDeUtils;
+import org.apache.pinot.core.query.request.context.ThreadTimer;
import org.apache.pinot.spi.utils.ByteArray;
import org.apache.pinot.spi.utils.BytesUtils;
-public class DataTableImplV2 implements DataTable {
- private static final int VERSION = 2;
+public class DataTableImplV2V3 implements DataTable {
Review comment:
I name it as DataTableImplV2V3 since V2 and V3 share a lot of common
logic. If V2 and V3 has major changes, as you suggest:
> Since we are anyway bumping up the version, how about we move the existing
metadata of key-value pairs to the end of file to keep consistency in the
format. So, all the metadata stuff (aka key-value pairs) + new positional stuff
can be a file footer.
If we do that, I vote for put V2 logic into DataTableImplV2 and V3 logic
into DataTableImplV3, and extract common logic (e.g. serialize/de-serialize
metada/dictionaryMap into DataTableUtils.java)
> move the existing metadata of key-value pairs to the end of file
Actually I considered that. I also considered to make metadata as a
`String[]` instead of `Map<String, String>` and make all meta data keys as enum
value. Also make "serialization_cpu_times_ns" as part of metadata. In other
words, "serialization_cpu_times_ns" is part of mate data and footer section
only contains meta data. In this way:
* all meta data is positional, we can replace values in metadata even after
data table is serialized. (`Map<String, String>` is not positional because when
loop over a hashmap, the order of items is not deterministic, but loop over of
an array, the order is deterministic)
* meta data previously is `Map<String, String>`, where we need to write
keys(type string) to byte buffer. When replaces as `String[]`, we don't write
the enum constant itself. Just the value (length+bytes) corresponding to the
ordinal/position of the constant. So less data is transfered between
server/broker.
But if we change in this way, as I previously stated, I vote to keep the
current DataTableImplV2.java as it is, and create a DataTableImplV3.java to put
all V3 logic (with extracting common into DataTableUtils.java ). Otherwise,
puting all V2/V3 logic in same file will make the code hard to read.
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