diff --git a/coordinator/src/main/scala/filodb.coordinator/queryplanner/ShardKeyRegexPlanner.scala b/coordinator/src/main/scala/filodb.coordinator/queryplanner/ShardKeyRegexPlanner.scala
index 14040f97fa..7a7897917d 100644
--- a/coordinator/src/main/scala/filodb.coordinator/queryplanner/ShardKeyRegexPlanner.scala
+++ b/coordinator/src/main/scala/filodb.coordinator/queryplanner/ShardKeyRegexPlanner.scala
@@ -117,7 +117,11 @@ class ShardKeyRegexPlanner(val dataset: Dataset,
       val result = walkLogicalPlanTree(logicalPlan, qContext)
       if (result.plans.size > 1) {
         MultiPartitionDistConcatExec(qContext, inProcessPlanDispatcher, result.plans)
-      } else result.plans.head
+      } else if (result.plans.size == 1) {
+        result.plans.head
+      } else {
+        EmptyResultExec(qContext, dataset.ref, inProcessPlanDispatcher)
+      }
     }
   }
 
@@ -148,21 +152,6 @@ class ShardKeyRegexPlanner(val dataset: Dataset,
   override def walkLogicalPlanTree(logicalPlan: LogicalPlan,
                                    qContext: QueryContext,
                                    forceInProcess: Boolean = false): PlanResult = {
-    // Materialize with the inner planner if:
-    //   - all plan data lies on one partition
-    //   - all RawSeries filters are identical
-    val qParams = qContext.origQueryParams.asInstanceOf[PromQlQueryParams]
-    val shardKeyFilterGroups = LogicalPlan.getRawSeriesFilters(logicalPlan)
-      .map(_.filter(cf => dataset.options.nonMetricShardColumns.contains(cf.column)))
-    val headFilters = shardKeyFilterGroups.headOption.map(_.toSet)
-    // Note: unchecked .get is OK here since it will only be called for each tail element.
-    val hasSameShardKeyFilters = shardKeyFilterGroups.tail.forall(_.toSet == headFilters.get)
-    val partitions = getShardKeys(logicalPlan)
-      .flatMap(filters => getPartitions(logicalPlan.replaceFilters(filters), qParams))
-    if (hasSameShardKeyFilters && isSinglePartition(partitions)) {
-      val plans = generateExec(logicalPlan, getShardKeys(logicalPlan), qContext)
-      return PlanResult(plans)
-    }
     logicalPlan match {
       case lp: ApplyMiscellaneousFunction  => materializeApplyMiscellaneousFunction(qContext, lp)
       case lp: ApplyInstantFunction        => materializeApplyInstantFunction(qContext, lp)
@@ -241,16 +230,21 @@ class ShardKeyRegexPlanner(val dataset: Dataset,
 
     // maps individual partitions to the set of shard-keys they contain.
     val partitionsToKeys = new mutable.HashMap[String, mutable.Buffer[Seq[ColumnFilter]]]()
+    val partitionSplitKeys = new mutable.ArrayBuffer[Seq[ColumnFilter]]
     keys.foreach { key =>
       val newLogicalPlan = logicalPlan.replaceFilters(key)
       // Querycontext should just have the part of query which has regex
       // For example for exp(sum(test{_ws_ = "demo", _ns_ =~ "App.*"})), sub queries should be
       // sum(test{_ws_ = "demo", _ns_ = "App-1"}), sum(test{_ws_ = "demo", _ns_ = "App-2"}) etc
       val newQueryParams = updateQueryParams(newLogicalPlan, queryParams)
-      getPartitions(newLogicalPlan, newQueryParams)
+      val partitions = getPartitions(newLogicalPlan, newQueryParams)
         .map(_.partitionName)
         .distinct
-        .foreach(part => partitionsToKeys.getOrElseUpdate(part, new mutable.ArrayBuffer).append(key))
+      if (partitions.size > 1) {
+        partitionSplitKeys.append(key)
+      } else {
+        partitions.foreach(part => partitionsToKeys.getOrElseUpdate(part, new mutable.ArrayBuffer).append(key))
+      }
     }
 
     // Sort each key into the same order as nonMetricShardKeys, then group keys with the same prefix.
@@ -261,6 +255,7 @@ class ShardKeyRegexPlanner(val dataset: Dataset,
         .map(key => key.sortBy(filter => nonMetricShardKeyColToIndex.getOrElse(filter.column, 0)))
         .groupBy(_.dropRight(1))
         .values
+        .flatMap(group => group.grouped(10))  // TODO(a_theimer)
       (partition, prefixGroups)
     }
 
@@ -269,7 +264,7 @@ class ShardKeyRegexPlanner(val dataset: Dataset,
                                     partitionToKeyGroups.values.headOption.map(_.size).getOrElse(0) > 1
 
     // Create one plan per key group.
-    partitionToKeyGroups.flatMap{ case (partition, keyGroups) =>
+    val groupedPlans = partitionToKeyGroups.flatMap{ case (partition, keyGroups) =>
       // NOTE: partition is intentionally unused; the inner planner will again determine which partitions own the data.
       keyGroups.map{ keys =>
         // Create a map of key->values, then create a ColumnFilter for each key.
@@ -296,6 +291,15 @@ class ShardKeyRegexPlanner(val dataset: Dataset,
         queryPlanner.materialize(newLogicalPlan, newQueryContext)
       }
     }.toSeq
+    val splitPlans = partitionSplitKeys.map{ key =>
+      // Update the LogicalPlan with the new partition-specific filters, then materialize.
+      val newLogicalPlan = logicalPlan.replaceFilters(key)
+      val newQueryParams = updateQueryParams(newLogicalPlan, queryParams)
+      val newQueryContext = qContext.copy(origQueryParams = newQueryParams, plannerParams = qContext.plannerParams.
+        copy(skipAggregatePresent = skipAggregatePresentValue))
+      queryPlanner.materialize(newLogicalPlan, newQueryContext)
+    }
+    groupedPlans ++ splitPlans
   }
   // scalastyle:on method.length
 
@@ -438,14 +442,27 @@ class ShardKeyRegexPlanner(val dataset: Dataset,
    * Sub query could be across multiple partitions so concatenate using MultiPartitionDistConcatExec
    * */
   private def materializeOthers(logicalPlan: LogicalPlan, queryContext: QueryContext): PlanResult = {
+    // Materialize with the inner planner if:
+    //   - all plan data lies on one partition
+    //   - all RawSeries filters are identical
+    val qParams = queryContext.origQueryParams.asInstanceOf[PromQlQueryParams]
+    val shardKeyFilterGroups = LogicalPlan.getRawSeriesFilters(logicalPlan)
+      .map(_.filter(cf => dataset.options.nonMetricShardColumns.contains(cf.column)))
+    val headFilters = shardKeyFilterGroups.headOption.map(_.toSet)
+    // Note: unchecked .get is OK here since it will only be called for each tail element.
+    val hasSameShardKeyFilters = shardKeyFilterGroups.tail.forall(_.toSet == headFilters.get)
+    val partitions = getShardKeys(logicalPlan)
+      .flatMap(filters => getPartitions(logicalPlan.replaceFilters(filters), qParams))
+    if (partitions.nonEmpty && hasSameShardKeyFilters && isSinglePartition(partitions)) {
+      val plans = generateExec(logicalPlan, getShardKeys(logicalPlan), queryContext)
+      return PlanResult(plans)
+    }
     val nonMetricShardKeyFilters =
       LogicalPlan.getNonMetricShardKeyFilters(logicalPlan, dataset.options.nonMetricShardColumns)
-    // For queries which don't have RawSeries filters like metadata and fixed scalar queries
-    val exec = if (nonMetricShardKeyFilters.head.isEmpty) queryPlanner.materialize(logicalPlan, queryContext)
-    else {
-      val execPlans = generateExecWithoutRegex(logicalPlan, nonMetricShardKeyFilters.head, queryContext)
-      if (execPlans.size == 1)
-        execPlans.head
+    val execPlans = generateExecWithoutRegex(logicalPlan, nonMetricShardKeyFilters.head, queryContext)
+    val exec = if (execPlans.size == 1) {
+      execPlans.head
+    } else if (execPlans.size > 1) {
       // TODO
       // here we essentially do not allow to optimize the physical plan for subqueries
       // as we concat the results with MultiPartitionDisConcatExec,
@@ -453,11 +470,12 @@ class ShardKeyRegexPlanner(val dataset: Dataset,
       // max_over_time(rate(foo{_ws_ = "demo", _ns_ =~ ".*Ns", instance = "Inst-1" }[10m])[1h:1m])
       // sum_over_time(foo{_ws_ = "demo", _ns_ =~ ".*Ns", instance = "Inst-1" }[5d:300s])
       // would have suboptimal performance. See subquery tests in PlannerHierarchySpec
-      else
-        MultiPartitionDistConcatExec(
-          queryContext, inProcessPlanDispatcher,
-          execPlans.sortWith((x, _) => !x.isInstanceOf[PromQlRemoteExec])
-        )
+      MultiPartitionDistConcatExec(
+        queryContext, inProcessPlanDispatcher,
+        execPlans.sortWith((x, _) => !x.isInstanceOf[PromQlRemoteExec])
+      )
+    } else {
+      EmptyResultExec(queryContext, dataset.ref, inProcessPlanDispatcher)
     }
     PlanResult(Seq(exec))
   }
diff --git a/query/src/main/scala/filodb/query/exec/StitchRvsExec.scala b/query/src/main/scala/filodb/query/exec/StitchRvsExec.scala
index 88e960d42d..e85bf0c0ae 100644
--- a/query/src/main/scala/filodb/query/exec/StitchRvsExec.scala
+++ b/query/src/main/scala/filodb/query/exec/StitchRvsExec.scala
@@ -81,9 +81,9 @@ object StitchRvsExec {
           // The second condition checks if these values are equal within the tolerable limits and if yes, do not
           // emit NaN.
           // TODO: Make the second check and tolerance configurable?
-          if (minsWithoutNan.tail.isEmpty) {
+          if (minsWithoutNan.size == 1) {
             minsWithoutNan.head
-          } else if (enableApproximatelyEqualCheck &&
+          } else if (minsWithoutNan.size > 1 && enableApproximatelyEqualCheck &&
             minsWithoutNan.map(x => (x.getDouble(1) * weight).toLong / weight).toSet.size == 1) {
             minsWithoutNan.head
           } else {