github.com/dolthub/go-mysql-server@v0.18.0/sql/plan/virtual_column_table.go (about)

     1  // Copyright 2023 Dolthub, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package plan
    16  
    17  import (
    18  	"fmt"
    19  	"strings"
    20  
    21  	"github.com/dolthub/go-mysql-server/sql"
    22  )
    23  
    24  // VirtualColumnTable is a sql.TableNode that combines a ResolvedTable with a Project, the latter of which is used
    25  // to add the values of virtual columns to the table.
    26  type VirtualColumnTable struct {
    27  	sql.Table
    28  	Projections []sql.Expression
    29  }
    30  
    31  var _ sql.TableWrapper = (*VirtualColumnTable)(nil)
    32  var _ sql.MutableTableWrapper = (*VirtualColumnTable)(nil)
    33  var _ sql.IndexedTable = (*VirtualColumnTable)(nil)
    34  
    35  func (v *VirtualColumnTable) Underlying() sql.Table {
    36  	return v.Table
    37  }
    38  
    39  func (v VirtualColumnTable) WithUnderlying(table sql.Table) sql.Table {
    40  	v.Table = table
    41  	return &v
    42  }
    43  
    44  // NewVirtualColumnTable creates a new VirtualColumnTable.
    45  func NewVirtualColumnTable(table sql.Table, projections []sql.Expression) *VirtualColumnTable {
    46  	return &VirtualColumnTable{
    47  		Table:       table,
    48  		Projections: projections,
    49  	}
    50  }
    51  
    52  func (v *VirtualColumnTable) LookupPartitions(context *sql.Context, lookup sql.IndexLookup) (sql.PartitionIter, error) {
    53  	// this will panic if we fail to correctly unwrap the underlying table during analysis to determine if it supports
    54  	// index lookups
    55  	return v.Table.(sql.IndexedTable).LookupPartitions(context, lookup)
    56  }
    57  
    58  func (v *VirtualColumnTable) String() string {
    59  	pr := sql.NewTreePrinter()
    60  	_ = pr.WriteNode("VirtualColumnTable")
    61  	children := make([]string, 2)
    62  	children[0] = fmt.Sprintf("name: %s", v.Name())
    63  	exprs := make([]string, len(v.Projections))
    64  	for i, expr := range v.Projections {
    65  		exprs[i] = expr.String()
    66  	}
    67  	children[1] = fmt.Sprintf("columns: [%s]", strings.Join(exprs, ", "))
    68  	_ = pr.WriteChildren(children...)
    69  
    70  	return pr.String()
    71  }
    72  
    73  func (v *VirtualColumnTable) DebugString() string {
    74  	pr := sql.NewTreePrinter()
    75  	_ = pr.WriteNode("VirtualColumnTable")
    76  	children := make([]string, 3)
    77  	children[0] = fmt.Sprintf("name: %s", v.Name())
    78  	exprs := make([]string, len(v.Projections))
    79  	for i, expr := range v.Projections {
    80  		exprs[i] = sql.DebugString(expr)
    81  	}
    82  
    83  	children[1] = fmt.Sprintf("columns: [%s]", strings.Join(exprs, ", "))
    84  	children[2] = TableDebugString(v.Table)
    85  	_ = pr.WriteChildren(children...)
    86  
    87  	return pr.String()
    88  }
    89  
    90  // FindVirtualColumnTable returns the plan.VirtualTableColumn being wrapped by the given table, if any.
    91  func FindVirtualColumnTable(table sql.Table) (*VirtualColumnTable, bool) {
    92  	if vct, ok := table.(*VirtualColumnTable); ok {
    93  		return vct, true
    94  	}
    95  	if tw, ok := table.(sql.TableWrapper); ok {
    96  		return FindVirtualColumnTable(tw.Underlying())
    97  	}
    98  	return nil, false
    99  }