Enhancement CBO (#2563) (#2566)

Author: ti-chi-bot

tikv-client/src/main/java/com/pingcap/tikv/predicates/TiKVScanAnalyzer.java

@@ -157,68 +157,72 @@ public TiDAGRequest buildTiDAGReq(
       TiTimestamp ts,
       TiDAGRequest dagRequest) {
 
-    TiKVScanPlan minPlan = null;
+    TiKVScanPlan minCostPlan = null;
     if (canUseTiKV) {
-      minPlan = buildTableScan(conditions, table, tableStatistics);
-    }
-    if (canUseTiFlash) {
-      // it is possible that only TiFlash plan exists due to isolation read.
-      TiKVScanPlan plan = buildTiFlashScan(columnList, conditions, table, tableStatistics);
-      if (minPlan == null || plan.getCost() < minPlan.getCost()) {
-        minPlan = plan;
-      }
-    } else if (canUseTiKV && allowIndexScan) {
-      minPlan.getFilters().forEach(dagRequest::addDowngradeFilter);
-      if (table.isPartitionEnabled()) {
-        // disable index scan
-      } else {
-        TiKVScanPlan minIndexPlan = null;
-        double minIndexCost = Double.MAX_VALUE;
-        for (TiIndexInfo index : table.getIndices()) {
-          if (table.isCommonHandle() && table.getPrimaryKey().equals(index)) {
-            continue;
-          }
+      // tikv table scan
+      minCostPlan = buildTableScan(conditions, table, tableStatistics);
+      // tikv index scan
+      if (allowIndexScan) {
+        minCostPlan.getFilters().forEach(dagRequest::addDowngradeFilter);
+        if (table.isPartitionEnabled()) {
+          // disable index scan
+        } else {
+          TiKVScanPlan minCostIndexPlan = null;
+          double minIndexCost = Double.MAX_VALUE;
+          for (TiIndexInfo index : table.getIndices()) {
+            if (table.isCommonHandle() && table.getPrimaryKey().equals(index)) {
+              continue;
+            }
 
-          if (supportIndexScan(index, table)) {
-            TiKVScanPlan plan =
-                buildIndexScan(columnList, conditions, index, table, tableStatistics, false);
-            if (plan.getCost() < minIndexCost) {
-              minIndexPlan = plan;
-              minIndexCost = plan.getCost();
+            if (supportIndexScan(index, table)) {
+              TiKVScanPlan plan =
+                  buildIndexScan(columnList, conditions, index, table, tableStatistics, false);
+              if (plan.getCost() < minIndexCost) {
+                minCostIndexPlan = plan;
+                minIndexCost = plan.getCost();
+              }
             }
           }
+          if (minCostIndexPlan != null
+              && (minIndexCost < minCostPlan.getCost() || useIndexScanFirst)) {
+            minCostPlan = minCostIndexPlan;
+          }
         }
-        if (minIndexPlan != null && (minIndexCost < minPlan.getCost() || useIndexScanFirst)) {
-          minPlan = minIndexPlan;
-        }
       }
     }
-    if (minPlan == null) {
+    if (canUseTiFlash) {
+      // it is possible that only TiFlash plan exists due to isolation read.
+      TiKVScanPlan plan = buildTiFlashScan(columnList, conditions, table, tableStatistics);
+      if (minCostPlan == null || plan.getCost() < minCostPlan.getCost()) {
+        minCostPlan = plan;
+      }
+    }
+    if (minCostPlan == null) {
       throw new TiClientInternalException(
           "No valid plan found for table '" + table.getName() + "'");
     }
 
-    TiStoreType minPlanStoreType = minPlan.getStoreType();
+    TiStoreType minCostPlanStoreType = minCostPlan.getStoreType();
     // TiKV should not use CHBlock as Encode Type.
-    if (minPlanStoreType == TiStoreType.TiKV
+    if (minCostPlanStoreType == TiStoreType.TiKV
         && dagRequest.getEncodeType() == EncodeType.TypeCHBlock) {
       dagRequest.setEncodeType(EncodeType.TypeChunk);
     }
-    // Set DAG Request's store type as minPlan's store type.
-    dagRequest.setStoreType(minPlanStoreType);
-
-    dagRequest.addRanges(minPlan.getKeyRanges());
-    dagRequest.setPrunedParts(minPlan.getPrunedParts());
-    dagRequest.addFilters(new ArrayList<>(minPlan.getFilters()));
-    if (minPlan.isIndexScan()) {
-      dagRequest.setIndexInfo(minPlan.getIndex());
+    // Set DAG Request's store type as minCostPlan's store type.
+    dagRequest.setStoreType(minCostPlanStoreType);
+
+    dagRequest.addRanges(minCostPlan.getKeyRanges());
+    dagRequest.setPrunedParts(minCostPlan.getPrunedParts());
+    dagRequest.addFilters(new ArrayList<>(minCostPlan.getFilters()));
+    if (minCostPlan.isIndexScan()) {
+      dagRequest.setIndexInfo(minCostPlan.getIndex());
       // need to set isDoubleRead to true for dagRequest in case of double read
-      dagRequest.setIsDoubleRead(minPlan.isDoubleRead());
+      dagRequest.setIsDoubleRead(minCostPlan.isDoubleRead());
     }
 
     dagRequest.setTableInfo(table);
     dagRequest.setStartTs(ts);
-    dagRequest.setEstimatedCount(minPlan.getEstimatedRowCount());
+    dagRequest.setEstimatedCount(minCostPlan.getEstimatedRowCount());
     return dagRequest;
   }