[GitHub] [iceberg] wypoon commented on a change in pull request #1508: Use schema at the time of the snapshot when reading a snapshot.

[GitBox]

wypoon commented on a change in pull request #1508:
URL: https://github.com/apache/iceberg/pull/1508#discussion_r501457611



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File path: core/src/main/java/org/apache/iceberg/BaseTable.java
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@@ -59,6 +60,45 @@ public Schema schema() {
     return ops.current().schema();
   }
 
+  @Override
+  public Schema schemaForSnapshot(long snapshotId) {
+    TableMetadata current = ops.current();
+    if (current.currentSnapshot() != null &&
+        current.currentSnapshot().snapshotId() == snapshotId) {
+      return current.schema();
+    }
+    Long snapshotTs = null;
+    for (HistoryEntry logEntry : current.snapshotLog()) {
+      if (logEntry.snapshotId() == snapshotId) {
+        snapshotTs = logEntry.timestampMillis();
+      }
+    }
+    Preconditions.checkArgument(snapshotTs != null,
+        "Cannot find a snapshot with id %s", snapshotId);
+    TableMetadata.MetadataLogEntry metadataLogEntry = null;
+    for (TableMetadata.MetadataLogEntry logEntry : current.previousFiles()) {
+      if (logEntry.timestampMillis() <= snapshotTs) {
+        metadataLogEntry = logEntry;
+      }
+    }
+    String metadataFile = metadataLogEntry.file();
+    TableMetadata metadata = TableMetadataParser.read(io(), metadataFile);
+    return metadata.schema();
+  }
+
+  @Override
+  public Schema schemaForSnapshotAsOfTime(long timestampMillis) {

Review comment:
       I have kept `schemaForSnapshotAsOfTime` for convenience. Since the 
`Table` API is unchanged, I think it is ok.




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