smiklosovic commented on code in PR #4411: URL: https://github.com/apache/cassandra/pull/4411#discussion_r2436431681
########## src/java/org/apache/cassandra/db/virtual/AbstractSchemaMetadataTable.java: ########## @@ -0,0 +1,299 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.cassandra.db.virtual; + +import org.apache.cassandra.db.DecoratedKey; +import org.apache.cassandra.db.marshal.CompositeType; +import org.apache.cassandra.db.marshal.UTF8Type; +import org.apache.cassandra.dht.LocalPartitioner; +import org.apache.cassandra.schema.ColumnMetadata; +import org.apache.cassandra.schema.KeyspaceMetadata; +import org.apache.cassandra.schema.Schema; +import org.apache.cassandra.schema.SchemaProvider; +import org.apache.cassandra.schema.TableMetadata; +import org.apache.cassandra.db.marshal.UserType; +import org.apache.cassandra.utils.NoSpamLogger; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.nio.ByteBuffer; +import java.util.concurrent.TimeUnit; + +import com.google.common.base.Strings; + +/** + * Abstract base class for virtual tables that expose metadata on schema elements. + * <p> + * This class provides a unified implementation for tables that expose metadata across: + * <ul> + * <li>Keyspaces - metadata on keyspaces</li> + * <li>Tables - metadata on tables</li> + * <li>Columns - metadata on columns</li> + * <li>User-Defined Types (UDTs) - metadata on UDTs</li> + * </ul> + * </p> + * <p> + * Subclasses must implement methods to extract the specific metadata field + * (e.g., comment, security label) from each schema element type. + * </p> + */ +abstract class AbstractSchemaMetadataTable extends AbstractVirtualTable +{ + private static final Logger logger = LoggerFactory.getLogger(AbstractSchemaMetadataTable.class); + private static final NoSpamLogger noSpamLogger = NoSpamLogger.getLogger(logger, 1L, TimeUnit.MINUTES); + + private static final String OBJECT_TYPE = "object_type"; + private static final String KEYSPACE_NAME = "keyspace_name"; + private static final String TABLE_NAME = "table_name"; + private static final String COLUMN_NAME = "column_name"; + private static final String UDT_NAME = "udt_name"; + + private final SchemaTableType schemaTableType; + + /** + * Schema object types that can have metadata. + */ + protected enum ObjectType + { + KEYSPACE, + TABLE, + COLUMN, + UDT; + + @Override + public String toString() + { + return name(); + } + + /** + * Parse object type string to enum. + * @param objectType the string representation of the object type + * @return ObjectType enum value or null if invalid + */ + static ObjectType parse(String objectType) + { + try + { + return ObjectType.valueOf(objectType); + } + catch (IllegalArgumentException e) + { + return null; + } + } + } + + protected enum SchemaTableType + { + COMMENT("schema_comments", "comment"), + SECURITY_LABEL("schema_security_labels", "security_label"); + + private final String tableName; + private final String columnName; + + SchemaTableType(String tableName, String columnName) + { + this.tableName = tableName; + this.columnName = columnName; + } + } + + AbstractSchemaMetadataTable(String keyspace, SchemaTableType schemaTableType) + { + super(TableMetadata.builder(keyspace, schemaTableType.tableName) + .kind(TableMetadata.Kind.VIRTUAL) + .partitioner(new LocalPartitioner(CompositeType.getInstance(UTF8Type.instance, UTF8Type.instance))) + .addPartitionKeyColumn(OBJECT_TYPE, UTF8Type.instance) + .addPartitionKeyColumn(KEYSPACE_NAME, UTF8Type.instance) + .addClusteringColumn(TABLE_NAME, UTF8Type.instance) + .addClusteringColumn(COLUMN_NAME, UTF8Type.instance) + .addClusteringColumn(UDT_NAME, UTF8Type.instance) + .addRegularColumn(schemaTableType.columnName, UTF8Type.instance) + .build()); + this.schemaTableType = schemaTableType; + } + + /** + * Extract metadata from a keyspace. + * @param keyspace the keyspace metadata + * @return the metadata value, or null if not present + */ + protected abstract String extractKeyspaceMetadata(KeyspaceMetadata keyspace); + + /** + * Extract metadata from a table. + * @param table the table metadata + * @return the metadata value, or null if not present + */ + protected abstract String extractTableMetadata(TableMetadata table); + + /** + * Extract metadata from a column. + * @param column the column metadata + * @return the metadata value, or null if not present + */ + protected abstract String extractColumnMetadata(ColumnMetadata column); + + /** + * Extract metadata from a UDT. + * @param udt the user-defined type + * @return the metadata value, or null if not present + */ + protected abstract String extractUdtMetadata(UserType udt); + + @Override + public DataSet data() + { + SimpleDataSet result = new SimpleDataSet(metadata()); + SchemaProvider schemaProvider = Schema.instance; + for (String keyspaceName : schemaProvider.getKeyspaces()) + { + KeyspaceMetadata keyspace = schemaProvider.getKeyspaceMetadata(keyspaceName); + if(keyspace == null) Review Comment: `if (keyspace` -- This is an automated message from the Apache Git Service. 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