Refactor s3select to support parquet. (#7023)

Also handle pretty formatted JSON documents.

pkg/s3select/sql/expr.go

@@ -0,0 +1,160 @@
+/*
+ * Minio Cloud Storage, (C) 2019 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sql
+
+import (
+	"fmt"
+)
+
+// Expr - a SQL expression type.
+type Expr interface {
+	AggregateValue() (*Value, error)
+	Eval(record Record) (*Value, error)
+	ReturnType() Type
+	Type() Type
+}
+
+// aliasExpr - aliases expression by alias.
+type aliasExpr struct {
+	alias string
+	expr  Expr
+}
+
+// String - returns string representation of this expression.
+func (expr *aliasExpr) String() string {
+	return fmt.Sprintf("(%v AS %v)", expr.expr, expr.alias)
+}
+
+// Eval - evaluates underlaying expression for given record and returns evaluated result.
+func (expr *aliasExpr) Eval(record Record) (*Value, error) {
+	return expr.expr.Eval(record)
+}
+
+// AggregateValue - returns aggregated value from underlaying expression.
+func (expr *aliasExpr) AggregateValue() (*Value, error) {
+	return expr.expr.AggregateValue()
+}
+
+// Type - returns underlaying expression type.
+func (expr *aliasExpr) Type() Type {
+	return expr.expr.Type()
+}
+
+// ReturnType - returns underlaying expression's return type.
+func (expr *aliasExpr) ReturnType() Type {
+	return expr.expr.ReturnType()
+}
+
+// newAliasExpr - creates new alias expression.
+func newAliasExpr(alias string, expr Expr) *aliasExpr {
+	return &aliasExpr{alias, expr}
+}
+
+// starExpr - asterisk (*) expression.
+type starExpr struct {
+}
+
+// String - returns string representation of this expression.
+func (expr *starExpr) String() string {
+	return "*"
+}
+
+// Eval - returns given args as map value.
+func (expr *starExpr) Eval(record Record) (*Value, error) {
+	return newRecordValue(record), nil
+}
+
+// AggregateValue - returns nil value.
+func (expr *starExpr) AggregateValue() (*Value, error) {
+	return nil, nil
+}
+
+// Type - returns record type.
+func (expr *starExpr) Type() Type {
+	return record
+}
+
+// ReturnType - returns record as return type.
+func (expr *starExpr) ReturnType() Type {
+	return record
+}
+
+// newStarExpr - returns new asterisk (*) expression.
+func newStarExpr() *starExpr {
+	return &starExpr{}
+}
+
+type valueExpr struct {
+	value *Value
+}
+
+func (expr *valueExpr) String() string {
+	return expr.value.String()
+}
+
+func (expr *valueExpr) Eval(record Record) (*Value, error) {
+	return expr.value, nil
+}
+
+func (expr *valueExpr) AggregateValue() (*Value, error) {
+	return expr.value, nil
+}
+
+func (expr *valueExpr) Type() Type {
+	return expr.value.Type()
+}
+
+func (expr *valueExpr) ReturnType() Type {
+	return expr.value.Type()
+}
+
+func newValueExpr(value *Value) *valueExpr {
+	return &valueExpr{value: value}
+}
+
+type columnExpr struct {
+	name string
+}
+
+func (expr *columnExpr) String() string {
+	return expr.name
+}
+
+func (expr *columnExpr) Eval(record Record) (*Value, error) {
+	value, err := record.Get(expr.name)
+	if err != nil {
+		return nil, errEvaluatorBindingDoesNotExist(err)
+	}
+
+	return value, nil
+}
+
+func (expr *columnExpr) AggregateValue() (*Value, error) {
+	return nil, nil
+}
+
+func (expr *columnExpr) Type() Type {
+	return column
+}
+
+func (expr *columnExpr) ReturnType() Type {
+	return column
+}
+
+func newColumnExpr(columnName string) *columnExpr {
+	return &columnExpr{name: columnName}
+}