From 3c03a6b94fc8709b1665a04e281e898bc53c07ee Mon Sep 17 00:00:00 2001
From: lidongsjtu <lidong_sjtu@126.com>
Date: Sun, 18 Oct 2015 11:21:13 +0800
Subject: [PATCH] KYLIN-1075 select [MeasureCol] from [FactTbl] is not
 supported

---
 .../kylin/query/enumerator/OLAPEnumerator.java     | 61 ++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/query/src/main/java/org/apache/kylin/query/enumerator/OLAPEnumerator.java b/query/src/main/java/org/apache/kylin/query/enumerator/OLAPEnumerator.java
index 38883f0..2f94d61 100644
--- a/query/src/main/java/org/apache/kylin/query/enumerator/OLAPEnumerator.java
+++ b/query/src/main/java/org/apache/kylin/query/enumerator/OLAPEnumerator.java
@@ -29,6 +29,11 @@ import org.apache.kylin.metadata.filter.CompareTupleFilter;
 import org.apache.kylin.metadata.filter.TimeConditionLiteralsReplacer;
 import org.apache.kylin.metadata.filter.TupleFilter;
 import org.apache.kylin.metadata.filter.TupleFilterSerializer;
+import org.apache.kylin.metadata.model.FunctionDesc;
+import org.apache.kylin.metadata.model.MeasureDesc;
+import org.apache.kylin.metadata.model.ParameterDesc;
+import org.apache.kylin.metadata.model.TblColRef;
+import org.apache.kylin.metadata.realization.SQLDigest;
 import org.apache.kylin.metadata.tuple.ITuple;
 import org.apache.kylin.metadata.tuple.ITupleIterator;
 import org.apache.kylin.query.relnode.OLAPContext;
@@ -110,6 +115,9 @@ public class OLAPEnumerator implements Enumerator<Object[]> {
         olapContext.filter = modifyTimeLiterals(olapContext.filter);
         olapContext.resetSQLDigest();
 
+        // hack simple select query for better result
+        hackNoGroupByAggregation();
+
         // query storage engine
         IStorageQuery storageEngine = StorageFactory.createQuery(olapContext.realization);
         ITupleIterator iterator = storageEngine.search(olapContext.storageContext, olapContext.getSQLDigest(), olapContext.returnTupleInfo);
@@ -160,4 +168,57 @@ public class OLAPEnumerator implements Enumerator<Object[]> {
         int threshold = Integer.valueOf(propThreshold);
         olapContext.storageContext.setThreshold(threshold);
     }
+
+    // Hack for better results
+    private void hackNoGroupByAggregation() {
+        SQLDigest sqlDigest = olapContext.getSQLDigest();
+
+        // If no group by and metric found, then it's simple query like select ... from ... where ...,
+        // But we have no raw data stored, in order to return better results, we hack to output sum of metric data,
+        if (sqlDigest.groupbyColumns.isEmpty() && sqlDigest.metricColumns.isEmpty()) {
+            logger.warn("No group by and aggregation found in this query, will hack some result for better look of output...");
+
+            // If it's select * from ...,
+            // We need to retrieve cube to manually add columns into sqlDigest,
+            // So that we have full-columns results as output.
+            boolean isSelectAll = sqlDigest.allColumns.isEmpty() || sqlDigest.allColumns.equals(sqlDigest.filterColumns);
+            for (TblColRef cubeColRef : olapContext.realization.getAllColumns()) {
+                if (cubeColRef.getTable().equals(sqlDigest.factTable) && (olapContext.realization.getAllDimensions().contains(cubeColRef) || isSelectAll)) {
+                    sqlDigest.allColumns.add(cubeColRef);
+                }
+            }
+
+            for (TblColRef colRef : sqlDigest.allColumns) {
+                // For dimension columns, take them as group by columns.
+                if (olapContext.realization.getAllDimensions().contains(colRef)) {
+                    sqlDigest.groupbyColumns.add(colRef);
+                }
+                // For measure columns, take them as metric columns with aggregation function SUM().
+                else {
+                    ParameterDesc colParameter = new ParameterDesc();
+                    colParameter.setType("column");
+                    colParameter.setValue(colRef.getName());
+                    FunctionDesc sumFunc = new FunctionDesc();
+                    sumFunc.setExpression("SUM");
+                    sumFunc.setParameter(colParameter);
+
+                    boolean measureHasSum = false;
+                    for (MeasureDesc colMeasureDesc : olapContext.realization.getMeasures()) {
+                        if (colMeasureDesc.getFunction().equals(sumFunc)) {
+                            measureHasSum = true;
+                            break;
+                        }
+                    }
+                    if (measureHasSum) {
+                        sqlDigest.aggregations.add(sumFunc);
+                    }
+                    else {
+                        logger.warn("SUM is not defined for measure column " + colRef + ", output will be meaningless.");
+                    }
+
+                    sqlDigest.metricColumns.add(colRef);
+                }
+            }
+        }
+    }
 }
-- 
2.3.8 (Apple Git-58)