[GitHub] [iceberg] dramaticlly commented on a diff in pull request #7613: Core: Minor metadata table code harmonization for readable_metrics

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

dramaticlly commented on code in PR #7613:
URL: https://github.com/apache/iceberg/pull/7613#discussion_r1198287876


##########
core/src/main/java/org/apache/iceberg/BaseFilesTable.java:
##########
@@ -192,14 +181,46 @@ private CloseableIterable<? extends ContentFile<?>> files(Schema fileProjection)
       }
     }
 
-    private StructLike withReadableMetrics(ContentFile<?> file, int metricsPosition) {
+    /**
+     * Given content file metadata, append a 'readable_metrics' column that return the file's
+     * metrics in human-readable form.
+     *
+     * @file content file metadata
+     * @param readableMetricsField projected "readable_metrics" field
+     * @return struct representing content file, with appended readable_metrics field
+     */
+    private StructLike withReadableMetrics(
+        ContentFile<?> file, Types.NestedField readableMetricsField) {
+      int metricsPosition = projection.columns().indexOf(readableMetricsField);
       int columnCount = projection.columns().size();

Review Comment:
   maybe we can reuse the `projectionColumnCount` as variable name above ?



##########
core/src/main/java/org/apache/iceberg/BaseFilesTable.java:
##########
@@ -192,14 +181,46 @@ private CloseableIterable<? extends ContentFile<?>> files(Schema fileProjection)
       }
     }
 
-    private StructLike withReadableMetrics(ContentFile<?> file, int metricsPosition) {
+    /**
+     * Given content file metadata, append a 'readable_metrics' column that return the file's
+     * metrics in human-readable form.
+     *
+     * @file content file metadata
+     * @param readableMetricsField projected "readable_metrics" field
+     * @return struct representing content file, with appended readable_metrics field
+     */
+    private StructLike withReadableMetrics(
+        ContentFile<?> file, Types.NestedField readableMetricsField) {
+      int metricsPosition = projection.columns().indexOf(readableMetricsField);
       int columnCount = projection.columns().size();
-      StructType projectedMetricType =
-          projection.findField(MetricsUtil.READABLE_METRICS).type().asStructType();
+
+      StructType projectedMetricType = readableMetricsField.type().asStructType();
       MetricsUtil.ReadableMetricsStruct readableMetrics =
           MetricsUtil.readableMetricsStruct(dataTableSchema, file, projectedMetricType);
-      return new ContentFileStructWithMetrics(
-          columnCount, metricsPosition, (StructLike) file, readableMetrics);
+      return new MetricsUtil.StructWithReadableMetrics(
+          (StructLike) file, readableMetrics, columnCount, metricsPosition);
+    }
+
+    /**
+     * Create a projection on content files metadata by removing virtual 'readable_column' and
+     * ensuring that the underlying metrics used to create that column are part of the final
+     * projection.
+     *
+     * @param projectionSchema projection to transform

Review Comment:
   nit: `projection to transform` read a bit weird as first time I read it I am not clear on why do we need to transform, maybe `requested projection` or `intended projection` which correspond to returning of actual projection ?



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