analyzer: fix pushdown of filters with repeated table names

Signed-off-by: Miguel Molina <miguel@erizocosmi.co>

Author: erizocosmico

sql/analyzer/filters.go

@@ -18,18 +18,22 @@ func (f filters) merge(f2 filters) {
 func exprToTableFilters(expr sql.Expression) filters {
 	filtersByTable := make(filters)
 	for _, expr := range splitExpression(expr) {
-		var tables []string
+		var seenTables = make(map[string]struct{})
+		var lastTable string
 		_, _ = expr.TransformUp(func(e sql.Expression) (sql.Expression, error) {
 			f, ok := e.(*expression.GetField)
 			if ok {
-				tables = append(tables, f.Table())
+				if _, ok := seenTables[f.Table()]; !ok {
+					seenTables[f.Table()] = struct{}{}
+					lastTable = f.Table()
+				}
 			}
 
 			return e, nil
 		})
 
-		if len(tables) == 1 {
-			filtersByTable[tables[0]] = append(filtersByTable[tables[0]], expr)
+		if len(seenTables) == 1 {
+			filtersByTable[lastTable] = append(filtersByTable[lastTable], expr)
 		}
 	}
 

sql/analyzer/filters_test.go

@@ -108,6 +108,21 @@ func TestExprToTableFilters(t *testing.T) {
 	require := require.New(t)
 	expr := expression.NewAnd(
 		expression.NewAnd(
+			expression.NewAnd(
+				expression.NewEquals(
+					expression.NewGetFieldWithTable(0, sql.Int64, "mytable", "f", false),
+					expression.NewLiteral(3.14, sql.Float64),
+				),
+				expression.NewGreaterThan(
+					expression.NewGetFieldWithTable(0, sql.Int64, "mytable", "f", false),
+					expression.NewLiteral(3., sql.Float64),
+				),
+			),
+			expression.NewIsNull(
+				expression.NewGetFieldWithTable(0, sql.Int64, "mytable2", "i2", false),
+			),
+		),
+		expression.NewOr(
 			expression.NewEquals(
 				expression.NewGetFieldWithTable(0, sql.Int64, "mytable", "f", false),
 				expression.NewLiteral(3.14, sql.Float64),
@@ -117,9 +132,6 @@ func TestExprToTableFilters(t *testing.T) {
 				expression.NewLiteral(3., sql.Float64),
 			),
 		),
-		expression.NewIsNull(
-			expression.NewGetFieldWithTable(0, sql.Int64, "mytable2", "i2", false),
-		),
 	)
 
 	expected := filters{
@@ -132,6 +144,16 @@ func TestExprToTableFilters(t *testing.T) {
 				expression.NewGetFieldWithTable(0, sql.Int64, "mytable", "f", false),
 				expression.NewLiteral(3., sql.Float64),
 			),
+			expression.NewOr(
+				expression.NewEquals(
+					expression.NewGetFieldWithTable(0, sql.Int64, "mytable", "f", false),
+					expression.NewLiteral(3.14, sql.Float64),
+				),
+				expression.NewGreaterThan(
+					expression.NewGetFieldWithTable(0, sql.Int64, "mytable", "f", false),
+					expression.NewLiteral(3., sql.Float64),
+				),
+			),
 		},
 		"mytable2": []sql.Expression{
 			expression.NewIsNull(