voonhous commented on code in PR #19205:
URL: https://github.com/apache/hudi/pull/19205#discussion_r3671829444
##########
hudi-client/hudi-client-common/src/main/java/org/apache/hudi/table/upgrade/NineToTenUpgradeHandler.java:
##########
@@ -34,6 +46,12 @@ public UpgradeDowngrade.TableConfigChangeSet upgrade(
HoodieEngineContext context,
String instantTime,
SupportsUpgradeDowngrade upgradeDowngradeHelper) {
- return new UpgradeDowngrade.TableConfigChangeSet();
+ HoodieTableConfig tableConfig =
+ upgradeDowngradeHelper.getTable(config,
context).getMetaClient().getTableConfig();
+ // Resolves from the legacy boolean for a version 9 table, since the mode
property is absent.
+ MetaFieldsMode metaFieldsMode = tableConfig.getMetaFieldsMode();
+ Map<ConfigProperty, String> propertiesToUpdate = Collections.singletonMap(
+ HoodieTableConfig.META_FIELDS_MODE, metaFieldsMode.name());
+ return new UpgradeDowngrade.TableConfigChangeSet(propertiesToUpdate,
Collections.emptySet());
Review Comment:
This is a scenario for upgrade + downgrade round trip.
**State A -- v9 table today (created pre-1.3 with virtual keys):**
hoodie.properties:
```
hoodie.table.version=9
hoodie.populate.meta.fields=false
```
Data files on disk have no meta columns. Readers resolve
`populateMetaFields() == false` and use the user's key field.
**State B -- after 9 -> 10**
if the upgrade removed the legacy property (the symmetry that
EightToNineUpgradeHandler follows for `PAYLOAD_CLASS_NAME` at :171-172 and
`PRECOMBINE_FIELD` at :240-241):
hoodie.properties:
```
hoodie.table.version=10
hoodie.meta.fields.mode=NONE
```
It is still correct -- at v10 the mode is the source of truth.
**State C -- after 10 -> 9 downgrade.**
`TenToNineDowngradeHandler:75` deletes `META_FIELDS_MODE`, and it has to: v9
cannot interpret it.
hoodie.properties:
```
hoodie.table.version=9
```
Neither property is present now.
**State D -- a v9 reader opens it**
`HoodieTableConfig.getMetaFieldsMode() (:1281)` falls back to
`legacyPopulateMetaFields()` -> `getStringOrDefault(POPULATE_META_FIELDS)` ->
`#defaultValue(true) (:338-341)` -> **ALL**.
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