[GitHub] [iceberg] RussellSpitzer commented on a diff in pull request #5376: Core: Add readable metrics columns to files metadata tables

[GitBox]

RussellSpitzer commented on code in PR #5376:
URL: https://github.com/apache/iceberg/pull/5376#discussion_r1017037292


##########
core/src/main/java/org/apache/iceberg/BaseFilesTable.java:
##########
@@ -140,42 +142,75 @@ protected CloseableIterable<FileScanTask> doPlanFiles() {
   }
 
   static class ManifestReadTask extends BaseFileScanTask implements DataTask {
+
+    private static final Set<Integer> READABLE_METRICS_FIELD_IDS =
+        TypeUtil.getProjectedIds(DataFile.READABLE_METRICS.type());
+    private static final Schema MIN_PROJECTION_FOR_READABLE_METRICS =
+        new Schema(
+            DataFile.COLUMN_SIZES,
+            DataFile.VALUE_COUNTS,
+            DataFile.NULL_VALUE_COUNTS,
+            DataFile.NAN_VALUE_COUNTS,
+            DataFile.LOWER_BOUNDS,
+            DataFile.UPPER_BOUNDS);
+
     private final FileIO io;
     private final Map<Integer, PartitionSpec> specsById;
     private final ManifestFile manifest;
-    private final Schema schema;
+    private final Schema dataTableSchema;
+    private final Schema projection;
 
     ManifestReadTask(
         Table table,
         ManifestFile manifest,
-        Schema schema,
+        Schema projection,
         String schemaString,
         String specString,
         ResidualEvaluator residuals) {
       super(DataFiles.fromManifest(manifest), null, schemaString, specString, 
residuals);
       this.io = table.io();
       this.specsById = Maps.newHashMap(table.specs());
       this.manifest = manifest;
-      this.schema = schema;
+      this.dataTableSchema = table.schema();
+      this.projection = projection;
     }
 
     @Override
     public CloseableIterable<StructLike> rows() {
-      return CloseableIterable.transform(manifestEntries(), file -> 
(StructLike) file);
+      if (projection.findColumnName(DataFile.READABLE_METRICS.fieldId()) == 
null) {
+        return CloseableIterable.transform(files(projection), file -> 
(StructLike) file);
+      } else {
+        Schema fileProjection = TypeUtil.selectNot(projection, 
READABLE_METRICS_FIELD_IDS);
+
+        // If readable_metrics is selected,
+        // original metrics columns need to be selected for derivation
+        Schema minProjection = TypeUtil.join(fileProjection, 
MIN_PROJECTION_FOR_READABLE_METRICS);

Review Comment:
   As we discussed offline I think this is a bit mislabeled, this is actually 
the maximal projection required correct? Ie if I only select VALUE_COUNTS for 
example, I do not actually need to get the rest of the metrics. I think this is 
fine for now since that's just an optimization but the name of the variable 
probably should be changed?



-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org

For queries about this service, please contact Infrastructure at:
us...@infra.apache.org


---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org
For additional commands, e-mail: issues-h...@iceberg.apache.org