[GitHub] [cassandra] adelapena commented on a diff in pull request #2110: CASSANDRA-18068 trunk: Allow to attach native masking functions to table columns

["adelapena (via GitHub)" <gi...@apache.org>]

adelapena commented on code in PR #2110:
URL: https://github.com/apache/cassandra/pull/2110#discussion_r1126264716


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src/java/org/apache/cassandra/cql3/functions/masking/ColumnMask.java:
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@@ -0,0 +1,231 @@
+/*
+ * 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.cql3.functions.masking;
+
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+
+import com.google.common.collect.ImmutableList;
+import org.apache.commons.lang3.StringUtils;
+
+import org.apache.cassandra.cql3.AssignmentTestable;
+import org.apache.cassandra.cql3.CQL3Type;
+import org.apache.cassandra.cql3.ColumnIdentifier;
+import org.apache.cassandra.cql3.CqlBuilder;
+import org.apache.cassandra.cql3.Term;
+import org.apache.cassandra.cql3.Terms;
+import org.apache.cassandra.cql3.functions.Function;
+import org.apache.cassandra.cql3.functions.FunctionName;
+import org.apache.cassandra.cql3.functions.FunctionResolver;
+import org.apache.cassandra.cql3.functions.ScalarFunction;
+import org.apache.cassandra.db.marshal.AbstractType;
+import org.apache.cassandra.db.marshal.ReversedType;
+import org.apache.cassandra.transport.ProtocolVersion;
+
+import static java.lang.String.format;
+import static org.apache.cassandra.cql3.statements.RequestValidations.invalidRequest;
+
+/**
+ * Dynamic data mask that can be applied to a schema column.
+ * <p>
+ * It consists on a partial application of a certain {@link MaskingFunction} to the values of a column, with the
+ * precondition that the type of any masked column is compatible with the type of the first argument of the function.
+ * <p>
+ * This partial application is meant to be associated to specific columns in the schema, acting as a mask for the values
+ * of those columns. It's associated to queries such as:
+ * <pre>
+ *    CREATE TABLE %t (k int PRIMARY KEY, v int MASKED WITH mask_inner(1, 1));
+ *    ALTER TABLE t ALTER v MASKED WITH mask_inner(2, 1);
+ *    ALTER TABLE t ALTER v DROP MASKED;
+ * </pre>
+ * Note that in the example above we are referencing the {@code mask_inner} function with two arguments. However, that
+ * CQL function actually has three arguments. The first argument is always ommitted when attaching the function to a
+ * schema column. The value of that first argument is always the value of the masked column, in this case an int.
+ */
+public class ColumnMask
+{
+    /** The CQL function used for masking. */
+    public final ScalarFunction function;
+
+    /** The values of the arguments of the partially applied masking function. */
+    public final List<ByteBuffer> partialArgumentValues;
+
+    public ColumnMask(ScalarFunction function, List<ByteBuffer> partialArgumentValues)
+    {
+        assert function.argTypes().size() == partialArgumentValues.size() + 1;
+        this.function = function;
+        this.partialArgumentValues = partialArgumentValues;
+    }
+
+    /**
+     * @return The types of the arguments of the partially applied masking function.
+     */
+    public List<AbstractType<?>> partialArgumentTypes()
+    {
+        List<AbstractType<?>> argTypes = function.argTypes();
+        return argTypes.size() == 1
+               ? Collections.emptyList()
+               : argTypes.subList(1, argTypes.size());
+    }
+
+    /**
+     * @return A copy of this mask for a version of its masked column that has its type reversed.
+     */
+    public ColumnMask withReversedType()
+    {
+        AbstractType<?> reversed = ReversedType.getInstance(function.argTypes().get(0));
+        List<AbstractType<?>> args = ImmutableList.<AbstractType<?>>builder()
+                                                  .add(reversed)
+                                                  .addAll(partialArgumentTypes())
+                                                  .build();
+        Function newFunction = FunctionResolver.get(function.name().keyspace, function.name(), args, null, null, null);
+        assert newFunction != null;
+        return new ColumnMask((ScalarFunction) newFunction, partialArgumentValues);
+    }
+
+    /**
+     * @param protocolVersion the used version of the transport protocol
+     * @param value           a column value to be masked
+     * @return the specified value after having been masked by the masked function
+     */
+    public ByteBuffer mask(ProtocolVersion protocolVersion, ByteBuffer value)
+    {
+        List<ByteBuffer> args = new ArrayList<>(partialArgumentValues.size() + 1);
+        args.add(value);
+        args.addAll(partialArgumentValues);
+        return function.execute(protocolVersion, args);
+    }
+
+    @Override
+    public boolean equals(Object o)
+    {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        ColumnMask mask = (ColumnMask) o;
+        return function.name().equals(mask.function.name())
+               && partialArgumentValues.equals(mask.partialArgumentValues);
+    }
+
+    @Override
+    public int hashCode()
+    {
+        return Objects.hash(function.name(), partialArgumentValues);
+    }
+
+    @Override
+    public String toString()
+    {
+        List<AbstractType<?>> types = partialArgumentTypes();
+        List<String> arguments = new ArrayList<>(types.size());
+        for (int i = 0; i < types.size(); i++)
+        {
+            CQL3Type type = types.get(i).asCQL3Type();
+            ByteBuffer value = partialArgumentValues.get(i);
+            arguments.add(type.toCQLLiteral(value, ProtocolVersion.CURRENT));
+        }
+        return format("%s(%s)", function.name(), StringUtils.join(arguments, ", "));
+    }
+
+    public void appendCqlTo(CqlBuilder builder)
+    {
+        builder.append(" MASKED WITH ").append(toString());
+    }
+
+    /**
+     * A parsed but not prepared column mask.
+     */
+    public final static class Raw
+    {
+        public final FunctionName name;
+        public final List<Term.Raw> rawPartialArguments;
+
+        public Raw(FunctionName name, List<Term.Raw> rawPartialArguments)
+        {
+            this.name = name;
+            this.rawPartialArguments = rawPartialArguments;
+        }
+
+        public ColumnMask prepare(String keyspace, String table, ColumnIdentifier column, AbstractType<?> type)
+        {
+            ScalarFunction function = findMaskingFunction(keyspace, table, column, type);
+

Review Comment:
   I'll remove them on commit.



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