derived_table.go

/*
Copyright 2021 The Vitess Authors.

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 semantics

import (
	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
	"vitess.io/vitess/go/vt/sqlparser"
	"vitess.io/vitess/go/vt/vterrors"
	"vitess.io/vitess/go/vt/vtgate/vindexes"
)

type derivedTable struct {
	tableName   string
	ASTNode     *sqlparser.AliasedTableExpr
	columnNames []string
	cols        []sqlparser.Expr
	tables      TableSet
}

var _ TableInfo = (*derivedTable)(nil)

func createDerivedTableForExpressions(expressions sqlparser.SelectExprs, tables []TableInfo, org originable) *derivedTable {
	vTbl := &derivedTable{}
	for _, selectExpr := range expressions {
		switch expr := selectExpr.(type) {
		case *sqlparser.AliasedExpr:
			vTbl.cols = append(vTbl.cols, expr.Expr)
			if expr.As.IsEmpty() {
				switch expr := expr.Expr.(type) {
				case *sqlparser.ColName:
					// for projections, we strip out the qualifier and keep only the column name
					vTbl.columnNames = append(vTbl.columnNames, expr.Name.String())
				default:
					vTbl.columnNames = append(vTbl.columnNames, sqlparser.String(expr))
				}
			} else {
				vTbl.columnNames = append(vTbl.columnNames, expr.As.String())
			}
		case *sqlparser.StarExpr:
			for _, table := range tables {
				vTbl.tables.MergeInPlace(table.getTableSet(org))
			}
		}
	}
	return vTbl
}

// Dependencies implements the TableInfo interface
func (dt *derivedTable) dependencies(colName string, org originable) (dependencies, error) {
	for i, name := range dt.columnNames {
		if name != colName {
			continue
		}
		recursiveDeps, qt := org.depsForExpr(dt.cols[i])

		directDeps := recursiveDeps
		if dt.ASTNode != nil {
			directDeps = org.tableSetFor(dt.ASTNode)
		}
		return createCertain(directDeps, recursiveDeps, qt), nil
	}

	if !dt.hasStar() {
		return &nothing{}, nil
	}

	recursive := dt.tables
	direct := org.tableSetFor(dt.ASTNode)

	return createUncertain(direct, recursive), nil
}

// IsInfSchema implements the TableInfo interface
func (dt *derivedTable) IsInfSchema() bool {
	return false
}

func (dt *derivedTable) matches(name sqlparser.TableName) bool {
	return dt.tableName == name.Name.String() && name.Qualifier.IsEmpty()
}

func (dt *derivedTable) authoritative() bool {
	return true
}

func (dt *derivedTable) Name() (sqlparser.TableName, error) {
	return dt.ASTNode.TableName()
}

func (dt *derivedTable) getExpr() *sqlparser.AliasedTableExpr {
	return dt.ASTNode
}

// GetVindexTable implements the TableInfo interface
func (dt *derivedTable) GetVindexTable() *vindexes.Table {
	return nil
}

func (dt *derivedTable) getColumns() []ColumnInfo {
	cols := make([]ColumnInfo, 0, len(dt.columnNames))
	for _, col := range dt.columnNames {
		cols = append(cols, ColumnInfo{
			Name: col,
		})
	}
	return cols
}

func (dt *derivedTable) hasStar() bool {
	return dt.tables.NumberOfTables() > 0
}

// GetTables implements the TableInfo interface
func (dt *derivedTable) getTableSet(_ originable) TableSet {
	return dt.tables
}

// GetExprFor implements the TableInfo interface
func (dt *derivedTable) getExprFor(s string) (sqlparser.Expr, error) {
	for i, colName := range dt.columnNames {
		if colName == s {
			return dt.cols[i], nil
		}
	}
	return nil, vterrors.NewErrorf(vtrpcpb.Code_NOT_FOUND, vterrors.BadFieldError, "Unknown column '%s' in 'field list'", s)
}

func (dt *derivedTable) checkForDuplicates() error {
	for i, name := range dt.columnNames {
		for j, name2 := range dt.columnNames {
			if i == j {
				continue
			}
			if name == name2 {
				return vterrors.NewErrorf(vtrpcpb.Code_INVALID_ARGUMENT, vterrors.DupFieldName, "Duplicate column name '%s'", name)
			}
		}
	}
	return nil
}