Don't use non-unique indexes as functional dependencies in AND expressions.

Author: nicktobey

enginetest/server_engine_test.go

@@ -267,6 +267,45 @@ func TestServerPreparedStatements(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "regression test for incorrectly setting QFlagMax1Row flag",
+			setup: []string{
+				"create table test(c0 int not null, c1 int not null, pk int primary key, key (c0, c1));",
+				"insert into test values (2, 3, 1), (5, 6, 4), (2, 3, 7);",
+			},
+			assertions: []serverScriptTestAssertion{
+				{
+					query: "select * from test where c0 = 2 and c1 = 3;",
+					expectedRows: []any{
+						[]uint64{uint64(2), uint64(3), uint64(1)},
+						[]uint64{uint64(2), uint64(3), uint64(7)},
+					},
+					checkRows: func(rows *gosql.Rows, expectedRows []any) (bool, error) {
+						var c0, c1, pk uint64
+						var rowNum int
+						for rows.Next() {
+							if err := rows.Scan(&c0, &c1, &pk); err != nil {
+								return false, err
+							}
+							if rowNum >= len(expectedRows) {
+								return false, nil
+							}
+							if c0 != expectedRows[rowNum].([]uint64)[0] {
+								return false, nil
+							}
+							if c1 != expectedRows[rowNum].([]uint64)[1] {
+								return false, nil
+							}
+							if pk != expectedRows[rowNum].([]uint64)[2] {
+								return false, nil
+							}
+							rowNum++
+						}
+						return true, nil
+					},
+				},
+			},
+		},
 	}
 
 	port, perr := findEmptyPort()
@@ -315,6 +354,8 @@ func TestServerPreparedStatements(t *testing.T) {
 					if assertion.expectErr {
 						require.Error(t, err)
 						return
+					} else {
+						require.NoError(t, err)
 					}
 					ok, err := assertion.checkRows(rows, assertion.expectedRows)
 					require.NoError(t, err)

sql/analyzer/costed_index_scan.go

@@ -1227,12 +1227,17 @@ func (c *indexCoster) costIndexScanAnd(filter *iScanAnd, s sql.Statistic, bucket
 		}
 	}
 
+	var conjFDs *sql.FuncDepSet
+	if idx.IsUnique() {
+		conjFDs = conj.getFds()
+	}
+
 	if exact.Len()+conj.applied.Len() == filter.childCnt() {
 		// matched all filters
-		return conj.hist, conj.getFds(), sql.NewFastIntSet(int(filter.id)), conj.missingPrefix, nil
+		return conj.hist, conjFDs, sql.NewFastIntSet(int(filter.id)), conj.missingPrefix, nil
 	}
 
-	return conj.hist, conj.getFds(), exact.Union(conj.applied), conj.missingPrefix, nil
+	return conj.hist, conjFDs, exact.Union(conj.applied), conj.missingPrefix, nil
 }
 
 func (c *indexCoster) costIndexScanOr(filter *iScanOr, s sql.Statistic, buckets []sql.HistogramBucket, ordinals map[string]int, idx sql.Index) ([]sql.HistogramBucket, *sql.FuncDepSet, bool, error) {
@@ -1679,6 +1684,7 @@ func (c *conjCollector) add(f *iScanLeaf) error {
 
 func (c *conjCollector) getFds() *sql.FuncDepSet {
 	constCols := sql.ColSet{}
+	// problem: they don't map based on positions: constants are based on the order in the secondary index key
 	c.constant.ForEach(func(i int) {
 		constCols.Add(sql.ColumnId(i))
 	})