wypoon commented on a change in pull request #1508:
URL: https://github.com/apache/iceberg/pull/1508#discussion_r501463178
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File path: spark2/src/main/java/org/apache/iceberg/spark/source/Reader.java
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@@ -165,13 +165,23 @@
TableProperties.PARQUET_BATCH_SIZE,
TableProperties.PARQUET_BATCH_SIZE_DEFAULT));
}
+ private Schema getTableSchema() {
+ if (snapshotId != null) {
+ return table.schemaForSnapshot(snapshotId);
+ } else if (asOfTimestamp != null) {
+ return table.schemaForSnapshotAsOfTime(asOfTimestamp);
+ } else {
+ return table.schema();
+ }
+ }
+
private Schema lazySchema() {
if (schema == null) {
if (requestedSchema != null) {
// the projection should include all columns that will be returned,
including those only used in filters
- this.schema = SparkSchemaUtil.prune(table.schema(), requestedSchema,
filterExpression(), caseSensitive);
+ this.schema = SparkSchemaUtil.prune(getTableSchema(), requestedSchema,
filterExpression(), caseSensitive);
} else {
- this.schema = table.schema();
+ this.schema = getTableSchema();
Review comment:
This is the only point I don't understand. As far as I can tell,
`BaseTableScan` is constructed with the user's requested schema. If the user is
wanting to read from an old snapshot, then they should be supplying a requested
schema compatible with the snapshot's schema. I couldn't see anything I needed
to change in `BaseTableScan`. If I'm missing something here, can you please
point out to me the parts I need to change?
I added a new test case where a requested schema is used, and that revealed
a bug in the spark2 `IcebergSource#createReader`. In that method, there is a
call to `SparkSchemaUtil.convert(Schema, StructType)` whose only purpose seems
to be to check that the requested `StructType` does not contain fields in the
`Schema` (for then the call would cause an exception), and here I needed to use
the snapshot `Schema` rather than the table `Schema`. Other than that, the
projection returned by the scan appears to be correct.
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