[GitHub] [iceberg] szehon-ho commented on a change in pull request #2358: Core: Add predicate push down for Partitions table

[GitBox <gi...@apache.org>]

szehon-ho commented on a change in pull request #2358:
URL: https://github.com/apache/iceberg/pull/2358#discussion_r606473839



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File path: core/src/main/java/org/apache/iceberg/PartitionsTable.java
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@@ -98,21 +105,46 @@ private DataTask task(TableScan scan) {
     return StaticDataTask.Row.of(partition.key, partition.recordCount, partition.fileCount);
   }
 
-  private static Iterable<Partition> partitions(Table table, Long snapshotId) {
+  private Iterable<Partition> partitions(StaticTableScan scan) {
+    CloseableIterable<FileScanTask> tasks = planTasks(scan);
+
     PartitionMap partitions = new PartitionMap(table.spec().partitionType());
-    TableScan scan = table.newScan();
+    for (FileScanTask task : tasks) {
+      partitions.get(task.file().partition()).update(task.file());
+    }
+    return partitions.all();
+  }
 
-    if (snapshotId != null) {
-      scan = scan.useSnapshot(snapshotId);
+  @VisibleForTesting
+  CloseableIterable<FileScanTask> planTasks(StaticTableScan scan) {
+    boolean caseSensitive = scan.isCaseSensitive();
+    boolean ignoreResiduals = scan.shouldIgnoreResiduals();
+    long snapshotId = scan.snapshot().snapshotId();
+
+    ManifestEvaluator eval = ManifestEvaluator.forPartitionFilter(
+        Projections.metadata(table.spec(), caseSensitive).project(scan.filter()),

Review comment:
       Hi yes, it's basically this but it's a little more.  I should have explained a bit more my thinking in the PR.
   
   Beyond transforming predicate "partition.x" => "x", there's also logic to handle predicates that don't have to do with the partitions, for example "record_count" > 0.  It seems the other Projections (InclusiveProjection/StrictProjection) were handling this logic (returning false for non-partition predicates, and all the and/or/not, etc),so I thought to re-use it.  It seems we have to 'project' those out, as  ManifestEvaluator Constructor tries bind predicates to the table's partitionSpec, and non-partition predicates will fail to be bound.
   
   I can probably use a cloned partition spec as you said, but the problem would still remain, and I would have to write my own ExpressionVisitor that does the same logic?  Or let me know if I misunderstand.




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