Cassandra 4.0 JVM port (Elassandra integration code)

This repository now ships the Cassandra 4.0.x + OpenSearch 1.3.x line. This note remains useful as an inventory of the API shifts that were required to move the Elassandra integration from the old 3.11-based line to the merged modern baseline:

Run scripts/use-cassandra-40-submodule.sh — aligns buildSrc/version.properties cassandra= with server/cassandra/build.xml base.version and checks out cassandra-4.0.x-elassandra.
Port Elassandra-specific classes against 4.0 APIs (types and method signatures differ from 3.11; mechanical rename is not enough).

Representative API shifts (non-exhaustive)

org.apache.cassandra.config.CFMetaData → org.apache.cassandra.schema.TableMetadata (and related schema types live under org.apache.cassandra.schema).
org.apache.cassandra.config.ColumnDefinition → org.apache.cassandra.schema.ColumnMetadata.
Secondary index Index.indexerFor — parameters moved from PartitionColumns / OpOrder.Group to RegularAndStaticColumns / WriteContext (see upstream org.apache.cassandra.index.Index in the 4.0 sources).
ExtendedElasticSecondaryIndex.validateOptions — prefer the overload taking TableMetadata when both static methods exist.

Primary touchpoints in this repo

org.elassandra.index.ElasticSecondaryIndex / ExtendedElasticSecondaryIndex
org.elassandra.cluster.SchemaManager, QueryManager, SchemaListener, ColumnDescriptor
org.opensearch.cluster.service.ClusterService and metadata services that bridge C* schema to OpenSearch mappings
Tests under server/src/test/java/org/elassandra/

For current-tree validation, run ./scripts/check-cassandra-submodule.sh and ./gradlew :server:compileJava with Java 11+.

Merged in-tree: ElasticSecondaryIndex / ExtendedElasticSecondaryIndex are updated for Cassandra 4.0 index APIs (TableMetadata, ColumnMetadata, RegularAndStaticColumns, WriteContext). The current merged tree uses OpenSearch bridge classes under org.opensearch.cluster / org.opensearch.index.mapper together with org.elassandra.* integration code.