SQL: Do not compile against matrix aggs module

Since matrix aggs module isn't on the classpath at runtime, we shouldn't
compile with it on the classpath. Doing so makes it possible for us to
die with dignity when we can't load the class. Which happens right now.

Original commit: elastic/x-pack-elasticsearch@6d2ca5e367

sql/server/build.gradle

@@ -4,7 +4,6 @@ dependencies {
   compile project(':x-pack-elasticsearch:sql:jdbc-proto')
   compile project(':x-pack-elasticsearch:sql:cli-proto')
   compile project(':x-pack-elasticsearch:sql:shared-proto')
-  provided "org.elasticsearch.plugin:aggs-matrix-stats-client:${project.versions.elasticsearch}"
   compile 'org.antlr:antlr4-runtime:4.5.3'
   provided "org.elasticsearch:elasticsearch:${project.versions.elasticsearch}"
 

sql/server/src/main/java/org/elasticsearch/xpack/sql/querydsl/agg/MatrixStatsAgg.java

@@ -6,10 +6,9 @@
 package org.elasticsearch.xpack.sql.querydsl.agg;
 
 import java.util.List;
-
+import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.search.aggregations.AggregationBuilder;
-
-import static org.elasticsearch.search.aggregations.MatrixStatsAggregationBuilders.matrixStats;
+import org.elasticsearch.xpack.sql.planner.PlanningException;
 
 public class MatrixStatsAgg extends LeafAgg {
 
@@ -18,10 +17,11 @@ public class MatrixStatsAgg extends LeafAgg {
     public MatrixStatsAgg(String id, String propertyPath, List<String> fields) {
         super(id, propertyPath, "<multi-field>");
         this.fields = fields;
+        throw new PlanningException("innerkey/matrix stats not handled (yet)", RestStatus.BAD_REQUEST);
     }
 
     @Override
     AggregationBuilder toBuilder() {
-        return matrixStats(id()).fields(fields);
+        throw new UnsupportedOperationException();
     }
 }