github.com/hasnat/dolt/go@v0.0.0-20210628190320-9eb5d843fbb7/libraries/doltcore/sqle/dfunctions/reset.go (about)

     1  // Copyright 2020 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 dfunctions
    16  
    17  import (
    18  	"fmt"
    19  	"strings"
    20  
    21  	"github.com/dolthub/go-mysql-server/sql"
    22  	"github.com/dolthub/go-mysql-server/sql/expression"
    23  
    24  	"github.com/dolthub/dolt/go/libraries/doltcore/sqle"
    25  	"github.com/dolthub/dolt/go/store/hash"
    26  )
    27  
    28  const (
    29  	resetFuncName = "reset"
    30  
    31  	resetHardParameter = "hard"
    32  )
    33  
    34  type ResetFunc struct {
    35  	expression.UnaryExpression
    36  }
    37  
    38  // NewDoltResetFunc creates a new ResetFunc expression.
    39  func NewResetFunc(ctx *sql.Context, e sql.Expression) sql.Expression {
    40  	return ResetFunc{expression.UnaryExpression{Child: e}}
    41  }
    42  
    43  // Eval implements the Expression interface.
    44  func (rf ResetFunc) Eval(ctx *sql.Context, row sql.Row) (interface{}, error) {
    45  	val, err := rf.Child.Eval(ctx, row)
    46  	if err != nil {
    47  		return nil, err
    48  	}
    49  	arg, ok := val.(string)
    50  	if !ok {
    51  		return nil, sql.ErrInvalidChildType.New(rf.Child.String(), rf.Child.Type(), sql.Text.Type())
    52  	}
    53  
    54  	dbName := ctx.GetCurrentDatabase()
    55  	dSess := sqle.DSessFromSess(ctx.Session)
    56  
    57  	var h hash.Hash
    58  	if strings.ToLower(arg) != resetHardParameter {
    59  		return nil, fmt.Errorf("invalid arugument to %s(): %s", resetFuncName, arg)
    60  	}
    61  
    62  	parent, _, err := dSess.GetHeadCommit(ctx, dbName)
    63  	if err != nil {
    64  		return nil, err
    65  	}
    66  
    67  	h, err = parent.HashOf()
    68  	if err != nil {
    69  		return nil, err
    70  	}
    71  
    72  	return h.String(), nil
    73  }
    74  
    75  // Resolved implements the Expression interface.
    76  func (rf ResetFunc) Resolved() bool {
    77  	return rf.Child.Resolved()
    78  }
    79  
    80  // String implements the Stringer interface.
    81  func (rf ResetFunc) String() string {
    82  	return fmt.Sprintf("RESET_HARD(%s)", rf.Child.String())
    83  }
    84  
    85  // IsNullable implements the Expression interface.
    86  func (rf ResetFunc) IsNullable() bool {
    87  	return false
    88  }
    89  
    90  // Children implements the Expression interface.
    91  func (rf ResetFunc) Children() []sql.Expression {
    92  	return []sql.Expression{rf.Child}
    93  }
    94  
    95  // WithChildren implements the Expression interface.
    96  func (rf ResetFunc) WithChildren(ctx *sql.Context, children ...sql.Expression) (sql.Expression, error) {
    97  	if len(children) != 1 {
    98  		return nil, sql.ErrInvalidChildrenNumber.New(rf, len(children), 1)
    99  	}
   100  	return NewResetFunc(ctx, children[0]), nil
   101  }
   102  
   103  // Type implements the Expression interface.
   104  func (rf ResetFunc) Type() sql.Type {
   105  	return sql.Text
   106  }