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https://issues.apache.org/jira/browse/DRILL-3623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15014506#comment-15014506
]
ASF GitHub Bot commented on DRILL-3623:
---------------------------------------
Github user sudheeshkatkam commented on a diff in the pull request:
https://github.com/apache/drill/pull/193#discussion_r45408655
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/handlers/FindLimit0Visitor.java
---
@@ -36,16 +48,62 @@
* executing a schema-only query.
*/
public class FindLimit0Visitor extends RelShuttleImpl {
- private static final org.slf4j.Logger logger =
org.slf4j.LoggerFactory.getLogger(FindLimit0Visitor.class);
+// private static final org.slf4j.Logger logger =
org.slf4j.LoggerFactory.getLogger(FindLimit0Visitor.class);
+
+ /**
+ * Values in the {@link
DrillConstExecutor#DRILL_TO_CALCITE_TYPE_MAPPING} map.
+ * + without {@link SqlTypeName#ANY} (avoid late binding)
+ * + without {@link SqlTypeName#VARBINARY} ({@link DrillValuesRel
values} does not support this)
+ * + with {@link SqlTypeName#CHAR} ({@link DrillValuesRel values}
supports this, but the above mapping does not
+ * contain this type.
+ */
+ private static final ImmutableSet<SqlTypeName> TYPES =
ImmutableSet.<SqlTypeName>builder()
+ .add(SqlTypeName.INTEGER, SqlTypeName.BIGINT, SqlTypeName.FLOAT,
SqlTypeName.DOUBLE, SqlTypeName.VARCHAR,
+ SqlTypeName.BOOLEAN, SqlTypeName.DATE, SqlTypeName.DECIMAL,
SqlTypeName.TIME, SqlTypeName.TIMESTAMP,
+ SqlTypeName.INTERVAL_YEAR_MONTH, SqlTypeName.INTERVAL_DAY_TIME,
SqlTypeName.MAP, SqlTypeName.ARRAY,
+ SqlTypeName.TINYINT, SqlTypeName.SMALLINT, SqlTypeName.CHAR)
+ .build();
private boolean contains = false;
+ /**
+ * Checks if the root portion of the RelNode tree contains a limit 0
pattern.
+ */
public static boolean containsLimit0(RelNode rel) {
FindLimit0Visitor visitor = new FindLimit0Visitor();
rel.accept(visitor);
return visitor.isContains();
}
+ /**
+ * If all field types of the given node are {@link #TYPES recognized
types}, then this method returns the tree:
+ * DrillLimitRel(0)
+ * \
+ * DrillValuesRel(field types)
+ * Otherwise, the method returns null.
+ */
+ public static DrillRel getValuesRelIfFullySchemaed(final RelNode rel) {
+ final List<RelDataTypeField> fieldList =
rel.getRowType().getFieldList();
+ final ImmutableList.Builder<RexLiteral> tupleBuilder = new
ImmutableList.Builder<>();
+ final RexBuilder literalBuilder = new
RexBuilder(rel.getCluster().getTypeFactory());
+ for (final RelDataTypeField field : fieldList) {
+ if (!TYPES.contains(field.getType().getSqlTypeName())) {
+ return null;
+ } else {
+ tupleBuilder.add((RexLiteral) literalBuilder.makeLiteral(null,
field.getType(), false));
+ }
+ }
+
+ final ImmutableList<ImmutableList<RexLiteral>> tuples = new
ImmutableList.Builder<ImmutableList<RexLiteral>>()
+ .add(tupleBuilder.build())
+ .build();
+ final RelTraitSet traits =
rel.getTraitSet().plus(DrillRel.DRILL_LOGICAL);
+ // TODO: ideally, we want the limit to be pushed into values
+ final DrillValuesRel values = new DrillValuesRel(rel.getCluster(),
rel.getRowType(), tuples, traits);
--- End diff --
I did this to avoid logical transformation completely, as this is an
exceptional case.
LogicalValues [allows an empty list of
tuples](https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/logical/LogicalValues.java#L101)
but as Jacques pointed out Drill does not handle that well (we use data to
encode types).
> Hive query hangs with limit 0 clause
> ------------------------------------
>
> Key: DRILL-3623
> URL: https://issues.apache.org/jira/browse/DRILL-3623
> Project: Apache Drill
> Issue Type: Bug
> Components: Storage - Hive
> Affects Versions: 1.1.0
> Environment: MapR cluster
> Reporter: Andries Engelbrecht
> Assignee: Sudheesh Katkam
> Fix For: Future
>
>
> Running a select * from hive.table limit 0 does not return (hangs).
> Select * from hive.table limit 1 works fine
> Hive table is about 6GB with 330 files with parquet using snappy compression.
> Data types are int, bigint, string and double.
> Querying directory with parquet files through the DFS plugin works fine
> select * from dfs.root.`/user/hive/warehouse/database/table` limit 0;
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