Github user arina-ielchiieva commented on a diff in the pull request:
https://github.com/apache/drill/pull/794#discussion_r108640631
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillOptiq.java
---
@@ -70,27 +70,65 @@
private static final org.slf4j.Logger logger =
org.slf4j.LoggerFactory.getLogger(DrillOptiq.class);
/**
- * Converts a tree of {@link RexNode} operators into a scalar expression
in Drill syntax.
+ * Converts a tree of {@link RexNode} operators into a scalar expression
in Drill syntax using one input.
+ *
+ * @param context parse context which contains planner settings
+ * @param input data input
+ * @param expr expression to be converted
+ * @return converted expression
*/
public static LogicalExpression toDrill(DrillParseContext context,
RelNode input, RexNode expr) {
- final RexToDrill visitor = new RexToDrill(context, input);
+ return toDrill(context, Lists.newArrayList(input), expr);
+ }
+
+ /**
+ * Converts a tree of {@link RexNode} operators into a scalar expression
in Drill syntax using multiple inputs.
+ *
+ * @param context parse context which contains planner settings
+ * @param inputs multiple data inputs
+ * @param expr expression to be converted
+ * @return converted expression
+ */
+ public static LogicalExpression toDrill(DrillParseContext context,
List<RelNode> inputs, RexNode expr) {
+ final RexToDrill visitor = new RexToDrill(context, inputs);
return expr.accept(visitor);
}
private static class RexToDrill extends
RexVisitorImpl<LogicalExpression> {
- private final RelNode input;
+ private final List<RelNode> inputs;
private final DrillParseContext context;
+ private final List<RelDataTypeField> fieldList;
- RexToDrill(DrillParseContext context, RelNode input) {
+ RexToDrill(DrillParseContext context, List<RelNode> inputs) {
super(true);
this.context = context;
- this.input = input;
+ this.inputs = inputs;
+ this.fieldList = Lists.newArrayList();
+ /*
+ Fields are enumerated by their presence order in input. Details
{@link org.apache.calcite.rex.RexInputRef}.
+ Thus we can merge field list from several inputs by adding them
into the list in order of appearance.
+ Each field index in the list will match field index in the
RexInputRef instance which will allow us
+ to retrieve field from filed list by index in {@link
#visitInputRef(RexInputRef)} method. Example:
+
+ Query: select t1.c1, t2.c1. t2.c2 from t1 inner join t2 on t1.c1
between t2.c1 and t2.c2
+
+ Input 1: $0
+ Input 2: $1, $2
+
+ Result: $0, $1, $2
+ */
+ for (RelNode input : inputs) {
--- End diff --
Yes, in `public LogicalExpression visitInputRef(RexInputRef inputRef)` we
determine to which input field belongs to. Before that we had only one input
thus we did simple get operation `input.getRowType().getFieldList().get(index)`
but now we have two inputs so we have to get operation on one input and if
field in not found try in the second. I could iterate over two inputs and do
get operation and once filed is found break the loop OR I could merge filed
list in one and do simple get operation `fieldList.get(index)`. For performance
reasons, I decided to merge filed lists in constructor and use them in `public
LogicalExpression visitInputRef(RexInputRef inputRef)` rather than iterating
over them for each field.
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