From d1456b02c06f11a04f060516d84ea18018727294 Mon Sep 17 00:00:00 2001
From: Devin Smith <devinsmith@deephaven.io>
Date: Fri, 2 Aug 2024 11:24:33 -0700
Subject: [PATCH] feat: Add TableTools.metaTable(TableDefinition) (#5885)

---
 .../java/io/deephaven/engine/table/Table.java |  3 +-
 .../engine/table/impl/TableDefaults.java      | 23 +---------
 .../io/deephaven/engine/util/TableTools.java  | 42 +++++++++++++++++++
 3 files changed, 45 insertions(+), 23 deletions(-)

diff --git a/engine/api/src/main/java/io/deephaven/engine/table/Table.java b/engine/api/src/main/java/io/deephaven/engine/table/Table.java
index 2fe32eab3b7..b4a101a397e 100644
--- a/engine/api/src/main/java/io/deephaven/engine/table/Table.java
+++ b/engine/api/src/main/java/io/deephaven/engine/table/Table.java
@@ -44,8 +44,7 @@ public interface Table extends
     TableDefinition getDefinition();
 
     /**
-     * Provides column metadata in Table form. Convenience method, behaves exactly the same as
-     * getDefinition().getColumnDefinitionsTable().
+     * Provides column metadata in Table form.
      *
      * @return A Table of metadata about this Table's columns.
      */
diff --git a/engine/table/src/main/java/io/deephaven/engine/table/impl/TableDefaults.java b/engine/table/src/main/java/io/deephaven/engine/table/impl/TableDefaults.java
index 219a9a75ab7..9600e9021d0 100644
--- a/engine/table/src/main/java/io/deephaven/engine/table/impl/TableDefaults.java
+++ b/engine/table/src/main/java/io/deephaven/engine/table/impl/TableDefaults.java
@@ -17,6 +17,7 @@
 import io.deephaven.api.util.ConcurrentMethod;
 import io.deephaven.engine.util.ColumnFormatting;
 import io.deephaven.engine.liveness.LivenessScopeStack;
+import io.deephaven.engine.util.TableTools;
 import io.deephaven.util.annotations.FinalDefault;
 
 import javax.annotation.Nullable;
@@ -47,27 +48,7 @@ default Table coalesce() {
     @ConcurrentMethod
     @FinalDefault
     default Table meta() {
-        List<String> columnNames = new ArrayList<>();
-        List<String> columnDataTypes = new ArrayList<>();
-        List<String> columnTypes = new ArrayList<>();
-        List<Boolean> columnPartitioning = new ArrayList<>();
-        for (ColumnDefinition<?> cDef : getDefinition().getColumns()) {
-            columnNames.add(cDef.getName());
-            final Class<?> dataType = cDef.getDataType();
-            final String dataTypeName = dataType.getCanonicalName();
-            columnDataTypes.add(dataTypeName == null ? dataType.getName() : dataTypeName);
-            columnTypes.add(cDef.getColumnType().name());
-            columnPartitioning.add(cDef.isPartitioning());
-        }
-        final String[] resultColumnNames = {"Name", "DataType", "ColumnType", "IsPartitioning"};
-        final Object[] resultValues = {
-                columnNames.toArray(String[]::new),
-                columnDataTypes.toArray(String[]::new),
-                columnTypes.toArray(String[]::new),
-                columnPartitioning.toArray(new Boolean[0]),
-        };
-
-        return new InMemoryTable(resultColumnNames, resultValues);
+        return TableTools.metaTable(getDefinition());
     }
 
     @Override
diff --git a/engine/table/src/main/java/io/deephaven/engine/util/TableTools.java b/engine/table/src/main/java/io/deephaven/engine/util/TableTools.java
index aa3bcfcaf7e..62a873325e2 100644
--- a/engine/table/src/main/java/io/deephaven/engine/util/TableTools.java
+++ b/engine/table/src/main/java/io/deephaven/engine/util/TableTools.java
@@ -13,6 +13,7 @@
 import io.deephaven.engine.rowset.RowSequence;
 import io.deephaven.engine.rowset.RowSetFactory;
 import io.deephaven.engine.table.*;
+import io.deephaven.engine.table.impl.InMemoryTable;
 import io.deephaven.engine.table.impl.perf.QueryPerformanceRecorder;
 import io.deephaven.internal.log.LoggerFactory;
 import io.deephaven.time.DateTimeUtils;
@@ -768,6 +769,47 @@ public static Table newTable(TableDefinition definition, ColumnHolder<?>... colu
         };
     }
 
+    /**
+     * Creates a metadata {@link Table} representing the columns in {@code definition}. Will include the following
+     * columns:
+     * <dl>
+     * <dt>Name</dt>
+     * <dd>{@link ColumnDefinition#getName()}</dd>
+     * <dt>DataType</dt>
+     * <dd>From {@link ColumnDefinition#getDataType()}, result of {@link Class#getCanonicalName()} if non-{@code null},
+     * else {@link Class#getName()}</dd>
+     * <dt>ColumnType</dt>
+     * <dd>{@code ColumnDefinition#getColumnType()}</dd>
+     * <dt>IsPartitioning</dt>
+     * <dd>{@link ColumnDefinition#isPartitioning()}</dd>
+     * </dl>
+     *
+     * @param definition the definition
+     * @return the metadata Table
+     */
+    public static Table metaTable(TableDefinition definition) {
+        List<String> columnNames = new ArrayList<>();
+        List<String> columnDataTypes = new ArrayList<>();
+        List<String> columnTypes = new ArrayList<>();
+        List<Boolean> columnPartitioning = new ArrayList<>();
+        for (ColumnDefinition<?> cDef : definition.getColumns()) {
+            columnNames.add(cDef.getName());
+            final Class<?> dataType = cDef.getDataType();
+            final String dataTypeName = dataType.getCanonicalName();
+            columnDataTypes.add(dataTypeName == null ? dataType.getName() : dataTypeName);
+            columnTypes.add(cDef.getColumnType().name());
+            columnPartitioning.add(cDef.isPartitioning());
+        }
+        final String[] resultColumnNames = {"Name", "DataType", "ColumnType", "IsPartitioning"};
+        final Object[] resultValues = {
+                columnNames.toArray(String[]::new),
+                columnDataTypes.toArray(String[]::new),
+                columnTypes.toArray(String[]::new),
+                columnPartitioning.toArray(new Boolean[0]),
+        };
+        return new InMemoryTable(resultColumnNames, resultValues);
+    }
+
     private static void checkSizes(ColumnHolder<?>[] columnHolders) {
         final int[] sizes = Arrays.stream(columnHolders).mapToInt(ColumnHolder::size).toArray();
         if (Arrays.stream(sizes).anyMatch(size -> size != sizes[0])) {