feat(trace): Support column lookup via index

This change adds support for looking up the column value through the
column index. This enables faster lookup when processing very large
traces.

2 files changed, 211 insertions, 6 deletions

diff --git a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/TableReader.kt b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/TableReader.kt
index b5e7669f..8a796e6c 100644
--- a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/TableReader.kt
+++ b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/TableReader.kt
@@ -34,34 +34,129 @@ public interface TableReader : AutoCloseable {
     public fun nextRow(): Boolean
 
     /**
+     * Resolve the index of the specified [column] for this reader.
+     *
+     * @param column The column to lookup.
+     * @return The zero-based index of the column or a negative value if the column is not present in this table.
+     */
+    public fun resolve(column: TableColumn<*>): Int
+
+    /**
      * Determine whether the [TableReader] supports the specified [column].
      */
-    public fun hasColumn(column: TableColumn<*>): Boolean
+    public fun hasColumn(column: TableColumn<*>): Boolean = resolve(column) >= 0
+
+    /**
+     * Determine whether the specified [column] has a `null` value for the current row.
+     *
+     * @param index The zero-based index of the column to check for a null value.
+     * @throws IllegalArgumentException if the column index is not valid for this reader.
+     * @return `true` if the column value for the current value has a `null` value, `false` otherwise.
+     */
+    public fun isNull(index: Int): Boolean
+
+    /**
+     * Obtain the object value of the column with the specified [index].
+     *
+     * @param index The zero-based index of the column to obtain the value for.
+     * @throws IllegalArgumentException if the column index is not valid for this reader.
+     * @return The object value of the column.
+     */
+    public fun get(index: Int): Any?
+
+    /**
+     * Obtain the boolean value of the column with the specified [index].
+     *
+     * @param index The zero-based index of the column to obtain the value for.
+     * @throws IllegalArgumentException if the column index is not valid for this reader.
+     * @return The boolean value of the column or `false` if the column is `null`.
+     */
+    public fun getBoolean(index: Int): Boolean
+
+    /**
+     * Obtain the integer value of the column with the specified [index].
+     *
+     * @param index The zero-based index of the column to obtain the value for.
+     * @throws IllegalArgumentException if the column index is not valid for this reader.
+     * @return The integer value of the column or `0` if the column is `null`.
+     */
+    public fun getInt(index: Int): Int
+
+    /**
+     * Obtain the double value of the column with the specified [index].
+     *
+     * @param index The zero-based index of the column to obtain the value for.
+     * @throws IllegalArgumentException if the column index is not valid for this reader.
+     * @return The long value of the column or `0` if the column is `null`.
+     */
+    public fun getLong(index: Int): Long
+
+    /**
+     * Obtain the double value of the column with the specified [index].
+     *
+     * @param index The zero-based index of the column to obtain the value for.
+     * @throws IllegalArgumentException if the column index is not valid for this reader.
+     * @return The double value of the column or [Double.NaN] if the column is `null`.
+     */
+    public fun getDouble(index: Int): Double
+
+    /**
+     * Determine whether the specified [column] has a `null` value for the current row.
+     *
+     * @param column The column to lookup.
+     * @throws IllegalArgumentException if the column is not valid for this table.
+     * @return `true` if the column value for the current value has a `null` value, `false` otherwise.
+     */
+    public fun isNull(column: TableColumn<*>): Boolean = isNull(resolve(column))
 
     /**
      * Obtain the value of the current column with type [T].
+     *
+     * @param column The column to obtain the value for.
+     * @throws IllegalArgumentException if the column is not valid for this reader.
+     * @return The object value of the column.
      */
-    public fun <T> get(column: TableColumn<T>): T
+    public fun <T> get(column: TableColumn<T>): T {
+        // This cast should always succeed since the resolve the index of the typed column
+        @Suppress("UNCHECKED_CAST")
+        return get(resolve(column)) as T
+    }
 
     /**
      * Read the specified [column] as boolean.
+     *
+     * @param column The column to obtain the value for.
+     * @throws IllegalArgumentException if the column is not valid for this reader.
+     * @return The boolean value of the column or `false` if the column is `null`.
      */
-    public fun getBoolean(column: TableColumn<Boolean>): Boolean
+    public fun getBoolean(column: TableColumn<Boolean>): Boolean = getBoolean(resolve(column))
 
     /**
      * Read the specified [column] as integer.
+     *
+     * @param column The column to obtain the value for.
+     * @throws IllegalArgumentException if the column is not valid for this reader.
+     * @return The integer value of the column or `0` if the column is `null`.
      */
-    public fun getInt(column: TableColumn<Int>): Int
+    public fun getInt(column: TableColumn<Int>): Int = getInt(resolve(column))
 
     /**
      * Read the specified [column] as long.
+     *
+     * @param column The column to obtain the value for.
+     * @throws IllegalArgumentException if the column is not valid for this reader.
+     * @return The long value of the column or `0` if the column is `null`.
      */
-    public fun getLong(column: TableColumn<Long>): Long
+    public fun getLong(column: TableColumn<Long>): Long = getLong(resolve(column))
 
     /**
      * Read the specified [column] as double.
+     *
+     * @param column The column to obtain the value for.
+     * @throws IllegalArgumentException if the column is not valid for this reader.
+     * @return The double value of the column or [Double.NaN] if the column is `null`.
      */
-    public fun getDouble(column: TableColumn<Double>): Double
+    public fun getDouble(column: TableColumn<Double>): Double = getDouble(resolve(column))
 
     /**
      * Closes the reader so that no further iteration or data access can be made.
diff --git a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/util/CompositeTableReader.kt b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/util/CompositeTableReader.kt
new file mode 100644
index 00000000..dafc0798
--- /dev/null
+++ b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/util/CompositeTableReader.kt
@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.trace.util
+
+import org.opendc.trace.TableColumn
+import org.opendc.trace.TableReader
+
+/**
+ * A helper class to chain multiple [TableReader]s.
+ */
+public abstract class CompositeTableReader : TableReader {
+    /**
+     * A flag to indicate that the reader has starting, meaning the user called [nextRow] at least once
+     * (and in turn [nextReader]).
+     */
+    private var hasStarted = false
+
+    /**
+     * The active [TableReader] instance.
+     */
+    private var delegate: TableReader? = null
+
+    /**
+     * Obtain the next [TableReader] instance to read from or `null` if there are no more readers to read from.
+     */
+    protected abstract fun nextReader(): TableReader?
+
+    override fun nextRow(): Boolean {
+        if (!hasStarted) {
+            assert(delegate == null) { "Duplicate initialization" }
+            delegate = nextReader()
+            hasStarted = true
+        }
+
+        var delegate = delegate
+
+        while (delegate != null) {
+            if (delegate.nextRow()) {
+                break
+            }
+
+            delegate.close()
+            delegate = nextReader()
+            this.delegate = delegate
+        }
+
+        return delegate != null
+    }
+
+    override fun resolve(column: TableColumn<*>): Int {
+        val delegate = delegate
+        return delegate?.resolve(column) ?: -1
+    }
+
+    override fun isNull(index: Int): Boolean {
+        val delegate = checkNotNull(delegate) { "Invalid reader state" }
+        return delegate.isNull(index)
+    }
+
+    override fun get(index: Int): Any? {
+        val delegate = checkNotNull(delegate) { "Invalid reader state" }
+        return delegate.get(index)
+    }
+
+    override fun getBoolean(index: Int): Boolean {
+        val delegate = checkNotNull(delegate) { "Invalid reader state" }
+        return delegate.getBoolean(index)
+    }
+
+    override fun getInt(index: Int): Int {
+        val delegate = checkNotNull(delegate) { "Invalid reader state" }
+        return delegate.getInt(index)
+    }
+
+    override fun getLong(index: Int): Long {
+        val delegate = checkNotNull(delegate) { "Invalid reader state" }
+        return delegate.getLong(index)
+    }
+
+    override fun getDouble(index: Int): Double {
+        val delegate = checkNotNull(delegate) { "Invalid reader state" }
+        return delegate.getDouble(index)
+    }
+
+    override fun close() {
+        delegate?.close()
+    }
+
+    override fun toString(): String = "CompositeTableReader"
+}