Fix purgeRealms in LocalPolarisMetaStoreManagerFactory does not clear entityCacheMap

[ayushtkn]

Describe the bug

LocalPolarisMetaStoreManagerFactory.purgeRealms() removes entries from sessionSupplierMap and metaStoreManagerMap but does not remove the corresponding entry from entityCacheMap.

polaris/polaris-core/src/main/java/org/apache/polaris/core/persistence/LocalPolarisMetaStoreManagerFactory.java

Lines 136 to 139 in 6382476

	sessionSupplierMap.remove(realm);
	metaStoreManagerMap.remove(realm);
	}

This means after a realm is purged and re-bootstrapped, getOrCreateEntityCache() returns the stale cache from the previous realm lifecycle — containing references to entities that no longer exist.

Additionally, purgeRealms is not synchronized, unlike the other map-mutating methods (bootstrapRealms, getOrCreateMetaStoreManager, getOrCreateSession), creating a potential race with
concurrent reads/writes to the shared maps.

To Reproduce

No response

Actual Behavior

Returns stale entires post rebootstrap

Expected Behavior

should return fresh entries after bootstrap

Additional context

No response

System information

No response

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment if you think it's still relevant.

[ayushtkn]

not stale