SourabhBadhya commented on code in PR #4672:
URL: https://github.com/apache/hive/pull/4672#discussion_r1336734175
##########
iceberg/iceberg-handler/src/main/java/org/apache/iceberg/mr/hive/HiveIcebergStorageHandler.java:
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@@ -1644,4 +1647,81 @@ public void
validatePartSpec(org.apache.hadoop.hive.ql.metadata.Table hmsTable,
}
}
}
+
+ /**
+ * A function to decide whether a given truncate query can perform a
metadata delete or not.
+ * If its not possible to perform metadata delete then try to perform a
positional delete.
+ * The steps to decide whether truncate is possible is as follows - <br>
+ * a. Create an expression based on the partition spec columns and partition
spec values. <br>
+ * b. Find files which match the expression using Apache Iceberg's FindFiles
API. <br>
+ * c. Do strict evaluation on whether the expression can clearly match all
rows in the file. <br>
+ * If for all files, the strict evaluation returns true, it means that we
safely delete all files
+ * by performing a metadata delete operation. If not, we must convert the
truncate to delete query
+ * which eventually performs a positional delete.
+ * @param hmsTable A Hive table instance.
+ * @param partitionSpec Map containing partition specification given by user.
+ * @return true if we can perform metadata delete, otherwise false.
+ * @throws SemanticException Exception raised when a partition transform is
being used
+ * or when partition column is not present in the table.
+ */
+ @Override
+ public boolean shouldTruncate(org.apache.hadoop.hive.ql.metadata.Table
hmsTable, Map<String, String> partitionSpec)
+ throws SemanticException {
+ Table table = IcebergTableUtil.getTable(conf, hmsTable.getTTable());
+ if (MapUtils.isEmpty(partitionSpec) || !isPartitionEvolution(table)) {
+ return true;
+ }
+
+ Map<String, PartitionField> partitionFieldMap =
Maps.newHashMapWithExpectedSize(table.spec().fields().size());
+ table.spec().fields().forEach(partField ->
partitionFieldMap.put(partField.name(), partField));
+ Expression finalExp = Expressions.alwaysTrue();
+ for (Map.Entry<String, String> entry : partitionSpec.entrySet()) {
+ String partColName = entry.getKey();
+ if (partitionFieldMap.containsKey(partColName)) {
+ PartitionField partitionField = partitionFieldMap.get(partColName);
+ Type resultType =
partitionField.transform().getResultType(table.schema()
+ .findField(partitionField.sourceId()).type());
+ TransformSpec.TransformType transformType =
IcebergTableUtil.getTransformType(partitionField.transform());
+ Object value = Conversions.fromPartitionString(resultType,
entry.getValue());
+ Iterable iterable = () -> Collections.singletonList(value).iterator();
+ if (transformType.equals(TransformSpec.TransformType.IDENTITY)) {
+ Expression boundPredicate = Expressions.in(partitionField.name(),
iterable);
+ finalExp = Expressions.and(finalExp, boundPredicate);
+ } else {
+ throw new SemanticException(
+ String.format("Partition transforms are not supported via
truncate operation: %s", partColName));
+ }
+ } else {
+ throw new SemanticException(String.format("No partition
column/transform by the name: %s", partColName));
+ }
+ }
+ FindFiles.Builder builder = new
FindFiles.Builder(table).withRecordsMatching(finalExp).includeColumnStats();
+ Set<DataFile> dataFiles =
Sets.newHashSet(Iterables.transform(builder.collect(), file -> file));
Review Comment:
Removed the lambda. Done.
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