Github user jinfengni commented on a diff in the pull request:
https://github.com/apache/drill/pull/397#discussion_r54765563
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/DrillFunctionRegistry.java
---
@@ -92,38 +94,110 @@ public DrillFunctionRegistry(ScanResult classpathScan)
{
}
public int size(){
- return methods.size();
+ return registeredFunctions.size();
}
/** Returns functions with given name. Function name is case
insensitive. */
public List<DrillFuncHolder> getMethods(String name) {
- return this.methods.get(name.toLowerCase());
+ return this.registeredFunctions.get(name.toLowerCase());
+ }
+
+ public Collection<DrillFuncHolder> getAllMethods() {
+ return
Collections.unmodifiableCollection(registeredFunctions.values());
}
public void register(DrillOperatorTable operatorTable) {
- SqlOperator op;
- for (Entry<String, Collection<DrillFuncHolder>> function :
methods.asMap().entrySet()) {
- Set<Integer> argCounts = Sets.newHashSet();
- String name = function.getKey().toUpperCase();
+ for (Entry<String, Collection<DrillFuncHolder>> function :
registeredFunctions.asMap().entrySet()) {
+ final ArrayListMultimap<Pair<Integer, Integer>, DrillFuncHolder>
functions = ArrayListMultimap.create();
+ final ArrayListMultimap<Integer, DrillFuncHolder> aggregateFunctions
= ArrayListMultimap.create();
+ final String name = function.getKey().toUpperCase();
+ boolean isDeterministic = true;
for (DrillFuncHolder func : function.getValue()) {
- if (argCounts.add(func.getParamCount())) {
- if (func.isAggregating()) {
- op = new DrillSqlAggOperator(name, func.getParamCount());
- } else {
- boolean isDeterministic;
- // prevent Drill from folding constant functions with types
that cannot be materialized
- // into literals
- if
(DrillConstExecutor.NON_REDUCIBLE_TYPES.contains(func.getReturnType().getMinorType()))
{
- isDeterministic = false;
- } else {
- isDeterministic = func.isDeterministic();
- }
- op = new DrillSqlOperator(name, func.getParamCount(),
func.getReturnType(), isDeterministic);
- }
- operatorTable.add(function.getKey(), op);
+ final int paramCount = func.getParamCount();
+ if(func.isAggregating()) {
+ aggregateFunctions.put(paramCount, func);
+ } else {
+ final Pair<Integer, Integer> argNumerRange =
getArgNumerRange(name, func);
+ functions.put(argNumerRange, func);
}
+
+ if(!func.isDeterministic()) {
+ isDeterministic = false;
+ }
+ }
+ for (Entry<Pair<Integer, Integer>, Collection<DrillFuncHolder>>
entry : functions.asMap().entrySet()) {
+ final DrillSqlOperator drillSqlOperator;
+ final Pair<Integer, Integer> range = entry.getKey();
+ final int max = range.getRight();
+ final int min = range.getLeft();
+ drillSqlOperator = new DrillSqlOperator(
+ name,
+ Lists.newArrayList(entry.getValue()),
+ min,
+ max,
+ isDeterministic);
+ operatorTable.add(name, drillSqlOperator);
+ }
+ for (Entry<Integer, Collection<DrillFuncHolder>> entry :
aggregateFunctions.asMap().entrySet()) {
+ operatorTable.add(name, new DrillSqlAggOperator(name,
Lists.newArrayList(entry.getValue()), entry.getKey()));
}
}
+
+ registerCalcitePlaceHolderFunction(operatorTable);
+ }
+
+ /**
+ * These {@link DrillSqlOperator} merely act as a placeholder so that
Calcite
+ * allows convert_to(), convert_from(), flatten(), date_part() functions
in SQL.
+ */
+ private void registerCalcitePlaceHolderFunction(DrillOperatorTable
operatorTable) {
+ final String convert_to = "CONVERT_TO";
+ final String convert_from = "CONVERT_FROM";
+ final String flatten = "FLATTEN";
+ final String date_part = "DATE_PART";
+
+ operatorTable.add(convert_to,
+ new DrillSqlOperator(convert_to,
+ 2,
+ true));
+ operatorTable.add(convert_from,
+ new DrillSqlOperator(convert_from,
+ 2,
+ true));
+ operatorTable.add(flatten,
+ new DrillSqlOperator(flatten,
+ 1,
+ true));
+ operatorTable.add(date_part,
+ new DrillSqlOperator(date_part,
+ 2,
+ true));
}
+ private Pair<Integer, Integer> getArgNumerRange(final String name, final
DrillFuncHolder func) {
+ switch(name.toUpperCase()) {
+ case "CONCAT":
+ return Pair.of(1, Integer.MAX_VALUE);
+
+ // Drill does not have a FunctionTemplate for the lpad/rpad with two
arguments.
+ // It relies on DrillOptiq.java to add a third dummy argument to be
acceptable
+ // by the FunctionTemplate in StringFunctions.java
+ case "LPAD":
+ case "RPAD":
+ return Pair.of(2, 3);
+
+ // Similar to the reason above, DrillOptiq.java is used for
rewritting
+ case "LTRIM":
+ case "RTRIM":
+ case "BTRIM":
+ return Pair.of(1, 2);
+
+ // Similar to the reason above, DrillOptiq.java is used for
rewritting
+ case "LENGTH":
+ return Pair.of(1, 2);
+
+ default:
+ return Pair.of(func.getParamCount(), func.getParamCount());
+ }
+ }
--- End diff --
@jacques-n , here is my understanding about the dummy functions @hsuanyi is
talking about.
For 'lpad' function, Calcite allows both 2 arguments or 3 arguments. Drill
has only implementation for the case of 3 arguments. What Drill did is
DrillOptiq will rewrite the case of 2 arguments into 3 arguments [2]. The dummy
function is for the case of 2 arguments, since Drill's run-time generate logic
does not need the implementation of 2 arguments at all, due to the rewrite in
DrillOptiq.
Another option is 1) to remove the rewrite in DrillOptiq and 2) add the
implementation for the case of 2 arguments (which is essentially same as the
one for 3 arguments). The new implementation for 2 arguments case is not dummy
at all.
[1]
https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/StringFunctions.java#L702-L707
[2]
https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillOptiq.java#L429-L434
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