Added support for add column and drop column

examples/scratch/README.md

@@ -56,6 +56,12 @@ ice delete nyc.taxis --dry-run=false
 # inspect
 ice describe
 
+# Alter table (add column)
+ice alter-table flowers.iris --operations '[{"operation": "add column", "column_name": "age", "type": "int", "comment": "user age"}]'
+
+# Alter table (drop column)
+ice alter-table flowers.iris --operations '[{"operation": "drop column", "column_name": "age"}]'
+
 # open ClickHouse shell, then try SQL below 
 clickhouse local
 ```

ice/src/main/java/com/altinity/ice/cli/Main.java

@@ -10,6 +10,7 @@
 package com.altinity.ice.cli;
 
 import ch.qos.logback.classic.Level;
+import com.altinity.ice.cli.internal.cmd.AlterTable;
 import com.altinity.ice.cli.internal.cmd.Check;
 import com.altinity.ice.cli.internal.cmd.CreateNamespace;
 import com.altinity.ice.cli.internal.cmd.CreateTable;
@@ -34,6 +35,7 @@
 import java.util.Base64;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Scanner;
 import java.util.stream.Collectors;
 import org.apache.iceberg.catalog.Namespace;
@@ -428,6 +430,36 @@ void deleteNamespace(
     }
   }
 
+  @CommandLine.Command(
+      name = "alter-table",
+      description =
+          "Alter table schema by adding or dropping columns. Supported operations: add column, drop column. Example: ice alter-table ns1.table1 --operations '[{\"operation\": \"add column\", \"column_name\": \"age\", \"type\": \"int\", \"comment\": \"user age\"}]'")
+  void alterTable(
+      @CommandLine.Parameters(
+              arity = "1",
+              paramLabel = "<name>",
+              description = "Table name (e.g. ns1.table1)")
+          String name,
+      @CommandLine.Option(
+              names = {"--operations"},
+              required = true,
+              description =
+                  "JSON array of operations: [{'operation': 'add column', 'column_name': 'age', 'type': 'int', 'comment': 'user age'}, {'operation': 'drop column', 'column_name': 'col_name'}]")
+          String operationsJson)
+      throws IOException {
+    try (RESTCatalog catalog = loadCatalog(this.configFile())) {
+      TableIdentifier tableId = TableIdentifier.parse(name);
+
+      ObjectMapper mapper = newObjectMapper();
+      List<Map<String, String>> operations =
+          mapper.readValue(
+              operationsJson,
+              mapper.getTypeFactory().constructCollectionType(List.class, Map.class));
+
+      AlterTable.run(catalog, tableId, operations);
+    }
+  }
+
   @CommandLine.Command(name = "delete", description = "Delete data from catalog.")
   void delete(
       @CommandLine.Parameters(

ice/src/main/java/com/altinity/ice/cli/internal/cmd/AlterTable.java

@@ -0,0 +1,189 @@
+/*
+ * Copyright (c) 2025 Altinity Inc and/or its affiliates. All rights reserved.
+ *
+ * Licensed 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
+ */
+package com.altinity.ice.cli.internal.cmd;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+import org.apache.iceberg.Table;
+import org.apache.iceberg.Transaction;
+import org.apache.iceberg.UpdateSchema;
+import org.apache.iceberg.catalog.Catalog;
+import org.apache.iceberg.catalog.TableIdentifier;
+import org.apache.iceberg.types.Types;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class AlterTable {
+  private static final Logger logger = LoggerFactory.getLogger(AlterTable.class);
+
+  // Static constants for column definition keys
+  private static final String OPERATION_KEY = "operation";
+  private static final String COLUMN_NAME_KEY = "column_name";
+  private static final String TYPE_KEY = "type";
+  private static final String COMMENT_KEY = "comment";
+
+  private AlterTable() {}
+
+  public enum OperationType {
+    ADD("add column"),
+    DROP("drop column");
+
+    private final String key;
+
+    OperationType(String key) {
+      this.key = key;
+    }
+
+    public String getKey() {
+      return key;
+    }
+
+    public static OperationType fromKey(String key) {
+      for (OperationType type : values()) {
+        if (type.key.equals(key)) {
+          return type;
+        }
+      }
+      throw new IllegalArgumentException("Unsupported operation type: " + key);
+    }
+  }
+
+  public record ColumnDefinition(
+      @JsonProperty("operation") String operation,
+      @JsonProperty("column_name") String columnName,
+      @JsonProperty("type") String type,
+      @JsonProperty("comment") String comment) {}
+
+  public static void run(
+      Catalog catalog, TableIdentifier tableId, List<Map<String, String>> operations)
+      throws IOException {
+
+    Table table = catalog.loadTable(tableId);
+
+    // Apply schema changes
+    Transaction transaction = table.newTransaction();
+    UpdateSchema updateSchema = transaction.updateSchema();
+
+    for (Map<String, String> operation : operations) {
+
+      // get the operation type
+      ColumnDefinition columnDef = parseColumnDefinitionMap(operation);
+      OperationType operationType = OperationType.fromKey(columnDef.operation());
+
+      switch (operationType) {
+        case ADD:
+          Types.NestedField field =
+              parseColumnType(columnDef.columnName(), columnDef.type(), columnDef.comment());
+          updateSchema.addColumn(columnDef.columnName(), field.type(), columnDef.comment());
+          logger.info("Adding column '{}' to table: {}", columnDef.columnName(), tableId);
+          break;
+        case DROP:
+          // Validate that the column exists
+          if (table.schema().findField(columnDef.columnName()) == null) {
+            throw new IllegalArgumentException(
+                "Column '" + columnDef.columnName() + "' does not exist in table: " + tableId);
+          }
+          updateSchema.deleteColumn(columnDef.columnName());
+          logger.info("Dropping column '{}' from table: {}", columnDef.columnName(), tableId);
+          break;
+        default:
+          throw new IllegalArgumentException("Unsupported operation type: " + operationType);
+      }
+    }
+
+    updateSchema.commit();
+    transaction.commitTransaction();
+
+    logger.info("Successfully applied {} operations to table: {}", operations.size(), tableId);
+  }
+
+  static ColumnDefinition parseColumnDefinitionMap(Map<String, String> operationMap) {
+    try {
+      String operation = operationMap.get(OPERATION_KEY);
+      String columnName = operationMap.get(COLUMN_NAME_KEY);
+      String type = operationMap.get(TYPE_KEY);
+      String comment = operationMap.get(COMMENT_KEY);
+
+      if (operation == null || operation.trim().isEmpty()) {
+        throw new IllegalArgumentException(OPERATION_KEY + " is required and cannot be empty");
+      }
+
+      if (columnName == null || columnName.trim().isEmpty()) {
+        throw new IllegalArgumentException(COLUMN_NAME_KEY + " is required and cannot be empty");
+      }
+
+      // For drop column operations, type is not required
+      OperationType operationType = OperationType.fromKey(operation);
+      if (operationType == OperationType.ADD) {
+        if (type == null || type.trim().isEmpty()) {
+          throw new IllegalArgumentException(
+              TYPE_KEY + " is required and cannot be empty for add column operations");
+        }
+        if (comment == null || comment.trim().isEmpty()) {
+          throw new IllegalArgumentException(
+              COMMENT_KEY + " is required and cannot be empty for add column operations");
+        }
+      }
+
+      return new ColumnDefinition(operation, columnName, type, comment);
+    } catch (Exception e) {
+      throw new IllegalArgumentException("Invalid column definition: " + e.getMessage());
+    }
+  }
+
+  private static Types.NestedField parseColumnType(String name, String type, String comment) {
+    Types.NestedField field;
+
+    switch (type.toLowerCase()) {
+      case "string":
+      case "varchar":
+        field = Types.NestedField.optional(-1, name, Types.StringType.get(), comment);
+        break;
+      case "int":
+      case "integer":
+        field = Types.NestedField.optional(-1, name, Types.IntegerType.get(), comment);
+        break;
+      case "long":
+      case "bigint":
+        field = Types.NestedField.optional(-1, name, Types.LongType.get(), comment);
+        break;
+      case "double":
+        field = Types.NestedField.optional(-1, name, Types.DoubleType.get(), comment);
+        break;
+      case "float":
+        field = Types.NestedField.optional(-1, name, Types.FloatType.get(), comment);
+        break;
+      case "boolean":
+        field = Types.NestedField.optional(-1, name, Types.BooleanType.get(), comment);
+        break;
+      case "date":
+        field = Types.NestedField.optional(-1, name, Types.DateType.get(), comment);
+        break;
+      case "timestamp":
+        field = Types.NestedField.optional(-1, name, Types.TimestampType.withoutZone(), comment);
+        break;
+      case "timestamptz":
+        field = Types.NestedField.optional(-1, name, Types.TimestampType.withZone(), comment);
+        break;
+      case "binary":
+        field = Types.NestedField.optional(-1, name, Types.BinaryType.get(), comment);
+        break;
+      default:
+        throw new IllegalArgumentException(
+            "Unsupported column type: "
+                + type
+                + ". Supported types: string, int, long, double, float, boolean, date, timestamp, timestamptz, binary");
+    }
+
+    return field;
+  }
+}

ice/src/test/java/com/altinity/ice/cli/internal/cmd/AlterTableTest.java

@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2025 Altinity Inc and/or its affiliates. All rights reserved.
+ *
+ * Licensed 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
+ */
+package com.altinity.ice.cli.internal.cmd;
+
+import static org.testng.Assert.assertEquals;
+import static org.testng.Assert.assertNull;
+
+import java.util.HashMap;
+import java.util.Map;
+import org.testng.annotations.Test;
+
+public class AlterTableTest {
+
+  @Test
+  public void testParseColumnDefinitionJson() {
+
+    Map<String, String> operation = new HashMap<>();
+    operation.put("operation", "add column");
+    operation.put("column_name", "age");
+    operation.put("type", "int");
+    operation.put("comment", "User age");
+    AlterTable.ColumnDefinition columnDef = AlterTable.parseColumnDefinitionMap(operation);
+
+    assertEquals(columnDef.columnName(), "age");
+    assertEquals(columnDef.type(), "int");
+    assertEquals(columnDef.comment(), "User age");
+  }
+
+  @Test(expectedExceptions = IllegalArgumentException.class)
+  public void testParseColumnDefinitionJsonWithoutComment() {
+
+    Map<String, String> operation = new HashMap<>();
+    operation.put("operation", "add column");
+    operation.put("column_name", "name");
+    operation.put("type", "string");
+    AlterTable.ColumnDefinition columnDef = AlterTable.parseColumnDefinitionMap(operation);
+
+    assertEquals(columnDef.columnName(), "name");
+    assertEquals(columnDef.type(), "string");
+    assertNull(columnDef.comment());
+  }
+
+  @Test(expectedExceptions = IllegalArgumentException.class)
+  public void testParseColumnDefinitionJsonMissingColumnName() {
+
+    Map<String, String> operation = new HashMap<>();
+    operation.put("operation", "add column");
+    operation.put("type", "int");
+    operation.put("comment", "User age");
+    AlterTable.parseColumnDefinitionMap(operation);
+  }
+
+  @Test(expectedExceptions = IllegalArgumentException.class)
+  public void testParseColumnDefinitionJsonMissingType() {
+
+    Map<String, String> operation = new HashMap<>();
+    operation.put("operation", "add column");
+    operation.put("column_name", "age");
+    operation.put("comment", "User age");
+    AlterTable.parseColumnDefinitionMap(operation);
+  }
+
+  @Test(expectedExceptions = IllegalArgumentException.class)
+  public void testParseColumnDefinitionJsonEmptyColumnName() {
+
+    Map<String, String> operation = new HashMap<>();
+    operation.put("operation", "add column");
+    operation.put("column_name", "");
+    operation.put("type", "int");
+    AlterTable.parseColumnDefinitionMap(operation);
+  }
+
+  @Test(expectedExceptions = IllegalArgumentException.class)
+  public void testParseColumnDefinitionJsonEmptyType() {
+
+    Map<String, String> operation = new HashMap<>();
+    operation.put("operation", "add column");
+    operation.put("column_name", "age");
+    operation.put("type", "");
+    AlterTable.parseColumnDefinitionMap(operation);
+  }
+
+  @Test(expectedExceptions = IllegalArgumentException.class)
+  public void testParseColumnDefinitionJsonInvalidJson() {
+
+    Map<String, String> operation = new HashMap<>();
+    operation.put("operation2", "add column");
+    operation.put("column_name", "age");
+    operation.put("type", "int");
+    AlterTable.parseColumnDefinitionMap(operation);
+  }
+
+  @Test
+  public void testOperationTypeFromKey() {
+    assertEquals(AlterTable.OperationType.fromKey("add column"), AlterTable.OperationType.ADD);
+    assertEquals(AlterTable.OperationType.fromKey("drop column"), AlterTable.OperationType.DROP);
+  }
+
+  @Test(expectedExceptions = IllegalArgumentException.class)
+  public void testOperationTypeFromKeyInvalid() {
+    AlterTable.OperationType.fromKey("invalid");
+  }
+
+  @Test
+  public void testParseColumnDefinitionMapForDropColumn() {
+
+    // Test drop column operation - only needs column_name
+    Map<String, String> operation = new HashMap<>();
+    operation.put("operation", "drop column");
+    operation.put("column_name", "age");
+    AlterTable.ColumnDefinition columnDef = AlterTable.parseColumnDefinitionMap(operation);
+
+    assertEquals(columnDef.operation(), "drop column");
+    assertEquals(columnDef.columnName(), "age");
+    assertNull(columnDef.type());
+    assertNull(columnDef.comment());
+  }
+}