Merge lp:~mmcm/akiban-server/sql-empty-index-range into lp:~akiban-technologies/akiban-server/trunk

[Mike McMahon]

Properly cost estimate and assemble an empty index scan UNION.

Index range processing merges constant conditions from a disjunction, assemblying the corresponding union of ranges. If each arm of the disjunction is impossible, that is, a contradictory conjunction, then the union is empty. Such contradictions are not always caught earlier. If so, estimate that index scan very cheaply, since it will not do any I/O and assemble it as an empty row set.

[Nathan Williams (nwilliams)]

Looks good.

review: Approve

=== modified file 'src/main/java/com/akiban/sql/optimizer/rule/OperatorAssembler.java'
--- src/main/java/com/akiban/sql/optimizer/rule/OperatorAssembler.java	2013-07-25 19:48:04 +0000
+++ src/main/java/com/akiban/sql/optimizer/rule/OperatorAssembler.java	2013-07-26 21:09:25 +0000
@@ -1248,6 +1248,11 @@
                         stream.rowType = stream.operator.rowType();
                     }
                 }
+                if (stream.operator == null) {
+                    stream.operator = API.valuesScan_Default(Collections.<BindableRow>emptyList(), 
+                                                             indexRowType);
+                    stream.rowType = indexRowType;
+                }
             }
             stream.fieldOffsets = new IndexFieldOffsets(indexScan, indexRowType);
             if (explainContext != null)

=== modified file 'src/main/java/com/akiban/sql/optimizer/rule/cost/PlanCostEstimator.java'
--- src/main/java/com/akiban/sql/optimizer/rule/cost/PlanCostEstimator.java	2013-05-24 21:45:54 +0000
+++ src/main/java/com/akiban/sql/optimizer/rule/cost/PlanCostEstimator.java	2013-07-26 21:09:25 +0000
@@ -400,6 +400,9 @@
                         else
                             cost = cost.union(acost);
                     }
+                    if (cost == null) {
+                        cost = new CostEstimate(0, 0); // No segments means no real scan.
+                    }
                     result = cost;
                 }
             }

=== modified file 'src/test/resources/com/akiban/sql/optimizer/rule/operator/README.txt'
--- src/test/resources/com/akiban/sql/optimizer/rule/operator/README.txt	2013-06-05 22:32:10 +0000
+++ src/test/resources/com/akiban/sql/optimizer/rule/operator/README.txt	2013-07-26 21:09:25 +0000
@@ -28,6 +28,8 @@
 
 select-6: index intersection with different column counts
 
+select-7: index scan with empty range (contradictory conditions)
+
 update-1: set to literal
 
 geospatial-1: compute max radius for N neighbors

=== added file 'src/test/resources/com/akiban/sql/optimizer/rule/operator/select-7.expected'
--- src/test/resources/com/akiban/sql/optimizer/rule/operator/select-7.expected	1970-01-01 00:00:00 +0000
+++ src/test/resources/com/akiban/sql/optimizer/rule/operator/select-7.expected	2013-07-26 21:09:25 +0000
@@ -0,0 +1,4 @@
+PhysicalSelect@65d036ae[name]
+  Project_Default(Field(1))
+    GroupLookup_Default(Index(test.customers.PRIMARY) -> test.customers)
+      ValuesScan_Default()
\ No newline at end of file

=== added file 'src/test/resources/com/akiban/sql/optimizer/rule/operator/select-7.sql'
--- src/test/resources/com/akiban/sql/optimizer/rule/operator/select-7.sql	1970-01-01 00:00:00 +0000
+++ src/test/resources/com/akiban/sql/optimizer/rule/operator/select-7.sql	2013-07-26 21:09:25 +0000
@@ -0,0 +1,1 @@
+SELECT name FROM customers WHERE (cid = 1 AND cid = 2) OR (cid = 3 AND cid = 4)
\ No newline at end of file