392 lines
13 KiB
Go
392 lines
13 KiB
Go
package expression
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import (
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"fmt"
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"sort"
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"strings"
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)
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// operationMode specifies the types of update operations that the
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// updateBuilder is going to represent. The const is in a string to use the
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// const value as a map key and as a string when creating the formatted
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// expression for the exprNodes.
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type operationMode string
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const (
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setOperation operationMode = "SET"
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removeOperation = "REMOVE"
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addOperation = "ADD"
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deleteOperation = "DELETE"
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)
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// Implementing the Sort interface
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type modeList []operationMode
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func (ml modeList) Len() int {
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return len(ml)
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}
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func (ml modeList) Less(i, j int) bool {
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return string(ml[i]) < string(ml[j])
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}
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func (ml modeList) Swap(i, j int) {
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ml[i], ml[j] = ml[j], ml[i]
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}
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// UpdateBuilder represents Update Expressions in DynamoDB. UpdateBuilders
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// are the building blocks of the Builder struct. Note that there are different
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// update operations in DynamoDB and an UpdateBuilder can represent multiple
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// update operations.
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// More Information at: http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.UpdateExpressions.html
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type UpdateBuilder struct {
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operationList map[operationMode][]operationBuilder
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}
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// operationBuilder represents specific update actions (SET, REMOVE, ADD,
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// DELETE). The mode specifies what type of update action the
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// operationBuilder represents.
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type operationBuilder struct {
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name NameBuilder
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value OperandBuilder
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mode operationMode
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}
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// buildOperation builds an exprNode from an operationBuilder. buildOperation
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// is called recursively by buildTree in order to create a tree structure
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// of exprNodes representing the parent/child relationships between
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// UpdateBuilders and operationBuilders.
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func (ob operationBuilder) buildOperation() (exprNode, error) {
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pathChild, err := ob.name.BuildOperand()
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if err != nil {
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return exprNode{}, err
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}
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node := exprNode{
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children: []exprNode{pathChild.exprNode},
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fmtExpr: "$c",
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}
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if ob.mode == removeOperation {
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return node, nil
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}
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valueChild, err := ob.value.BuildOperand()
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if err != nil {
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return exprNode{}, err
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}
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node.children = append(node.children, valueChild.exprNode)
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switch ob.mode {
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case setOperation:
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node.fmtExpr += " = $c"
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case addOperation, deleteOperation:
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node.fmtExpr += " $c"
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default:
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return exprNode{}, fmt.Errorf("build update error: build operation error: unsupported mode: %v", ob.mode)
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}
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return node, nil
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}
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// Delete returns an UpdateBuilder representing one Delete operation for
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// DynamoDB Update Expressions. The argument name should specify the item
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// attribute and the argument value should specify the value to be deleted. The
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// resulting UpdateBuilder can be used as an argument to the WithUpdate() method
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// for the Builder struct.
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//
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// Example:
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//
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// // update represents the delete operation to delete the string value
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// // "subsetToDelete" from the item attribute "pathToList"
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// update := expression.Delete(expression.Name("pathToList"), expression.Value("subsetToDelete"))
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//
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// // Adding more update methods
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// anotherUpdate := update.Remove(expression.Name("someName"))
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// // Creating a Builder
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// builder := Update(update)
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//
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// Expression Equivalent:
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//
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// expression.Delete(expression.Name("pathToList"), expression.Value("subsetToDelete"))
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// // let :del be an ExpressionAttributeValue representing the value
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// // "subsetToDelete"
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// "DELETE pathToList :del"
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func Delete(name NameBuilder, value ValueBuilder) UpdateBuilder {
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emptyUpdateBuilder := UpdateBuilder{}
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return emptyUpdateBuilder.Delete(name, value)
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}
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// Delete adds a Delete operation to the argument UpdateBuilder. The
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// argument name should specify the item attribute and the argument value should
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// specify the value to be deleted. The resulting UpdateBuilder can be used as
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// an argument to the WithUpdate() method for the Builder struct.
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//
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// Example:
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//
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// // Let update represent an already existing update expression. Delete()
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// // adds the operation to delete the value "subsetToDelete" from the item
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// // attribute "pathToList"
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// update := update.Delete(expression.Name("pathToList"), expression.Value("subsetToDelete"))
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//
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// // Adding more update methods
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// anotherUpdate := update.Remove(expression.Name("someName"))
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// // Creating a Builder
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// builder := Update(update)
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//
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// Expression Equivalent:
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//
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// Delete(expression.Name("pathToList"), expression.Value("subsetToDelete"))
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// // let :del be an ExpressionAttributeValue representing the value
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// // "subsetToDelete"
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// "DELETE pathToList :del"
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func (ub UpdateBuilder) Delete(name NameBuilder, value ValueBuilder) UpdateBuilder {
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if ub.operationList == nil {
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ub.operationList = map[operationMode][]operationBuilder{}
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}
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ub.operationList[deleteOperation] = append(ub.operationList[deleteOperation], operationBuilder{
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name: name,
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value: value,
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mode: deleteOperation,
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})
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return ub
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}
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// Add returns an UpdateBuilder representing the Add operation for DynamoDB
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// Update Expressions. The argument name should specify the item attribute and
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// the argument value should specify the value to be added. The resulting
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// UpdateBuilder can be used as an argument to the WithUpdate() method for the
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// Builder struct.
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//
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// Example:
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//
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// // update represents the add operation to add the value 5 to the item
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// // attribute "aPath"
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// update := expression.Add(expression.Name("aPath"), expression.Value(5))
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//
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// // Adding more update methods
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// anotherUpdate := update.Remove(expression.Name("someName"))
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// // Creating a Builder
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// builder := Update(update)
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//
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// Expression Equivalent:
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//
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// expression.Add(expression.Name("aPath"), expression.Value(5))
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// // Let :five be an ExpressionAttributeValue representing the value 5
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// "ADD aPath :5"
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func Add(name NameBuilder, value ValueBuilder) UpdateBuilder {
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emptyUpdateBuilder := UpdateBuilder{}
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return emptyUpdateBuilder.Add(name, value)
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}
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// Add adds an Add operation to the argument UpdateBuilder. The argument
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// name should specify the item attribute and the argument value should specify
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// the value to be added. The resulting UpdateBuilder can be used as an argument
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// to the WithUpdate() method for the Builder struct.
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//
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// Example:
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//
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// // Let update represent an already existing update expression. Add() adds
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// // the operation to add the value 5 to the item attribute "aPath"
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// update := update.Add(expression.Name("aPath"), expression.Value(5))
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//
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// // Adding more update methods
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// anotherUpdate := update.Remove(expression.Name("someName"))
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// // Creating a Builder
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// builder := Update(update)
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//
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// Expression Equivalent:
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//
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// Add(expression.Name("aPath"), expression.Value(5))
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// // Let :five be an ExpressionAttributeValue representing the value 5
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// "ADD aPath :5"
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func (ub UpdateBuilder) Add(name NameBuilder, value ValueBuilder) UpdateBuilder {
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if ub.operationList == nil {
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ub.operationList = map[operationMode][]operationBuilder{}
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}
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ub.operationList[addOperation] = append(ub.operationList[addOperation], operationBuilder{
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name: name,
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value: value,
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mode: addOperation,
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})
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return ub
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}
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// Remove returns an UpdateBuilder representing the Remove operation for
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// DynamoDB Update Expressions. The argument name should specify the item
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// attribute to delete. The resulting UpdateBuilder can be used as an argument
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// to the WithUpdate() method for the Builder struct.
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//
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// Example:
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//
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// // update represents the remove operation to remove the item attribute
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// // "itemToRemove"
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// update := expression.Remove(expression.Name("itemToRemove"))
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//
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// // Adding more update methods
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// anotherUpdate := update.Remove(expression.Name("someName"))
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// // Creating a Builder
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// builder := Update(update)
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//
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// Expression Equivalent:
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//
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// expression.Remove(expression.Name("itemToRemove"))
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// "REMOVE itemToRemove"
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func Remove(name NameBuilder) UpdateBuilder {
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emptyUpdateBuilder := UpdateBuilder{}
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return emptyUpdateBuilder.Remove(name)
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}
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// Remove adds a Remove operation to the argument UpdateBuilder. The
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// argument name should specify the item attribute to delete. The resulting
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// UpdateBuilder can be used as an argument to the WithUpdate() method for the
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// Builder struct.
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//
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// Example:
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//
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// // Let update represent an already existing update expression. Remove()
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// // adds the operation to remove the item attribute "itemToRemove"
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// update := update.Remove(expression.Name("itemToRemove"))
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//
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// // Adding more update methods
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// anotherUpdate := update.Remove(expression.Name("someName"))
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// // Creating a Builder
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// builder := Update(update)
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//
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// Expression Equivalent:
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//
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// Remove(expression.Name("itemToRemove"))
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// "REMOVE itemToRemove"
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func (ub UpdateBuilder) Remove(name NameBuilder) UpdateBuilder {
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if ub.operationList == nil {
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ub.operationList = map[operationMode][]operationBuilder{}
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}
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ub.operationList[removeOperation] = append(ub.operationList[removeOperation], operationBuilder{
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name: name,
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mode: removeOperation,
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})
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return ub
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}
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// Set returns an UpdateBuilder representing the Set operation for DynamoDB
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// Update Expressions. The argument name should specify the item attribute to
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// modify. The argument OperandBuilder should specify the value to modify the
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// the item attribute to. The resulting UpdateBuilder can be used as an argument
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// to the WithUpdate() method for the Builder struct.
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//
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// Example:
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//
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// // update represents the set operation to set the item attribute
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// // "itemToSet" to the value "setValue" if the item attribute does not
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// // exist yet. (conditional write)
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// update := expression.Set(expression.Name("itemToSet"), expression.IfNotExists(expression.Name("itemToSet"), expression.Value("setValue")))
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//
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// // Adding more update methods
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// anotherUpdate := update.Remove(expression.Name("someName"))
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// // Creating a Builder
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// builder := Update(update)
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//
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// Expression Equivalent:
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//
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// expression.Set(expression.Name("itemToSet"), expression.IfNotExists(expression.Name("itemToSet"), expression.Value("setValue")))
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// // Let :val be an ExpressionAttributeValue representing the value
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// // "setValue"
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// "SET itemToSet = :val"
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func Set(name NameBuilder, operandBuilder OperandBuilder) UpdateBuilder {
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emptyUpdateBuilder := UpdateBuilder{}
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return emptyUpdateBuilder.Set(name, operandBuilder)
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}
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// Set adds a Set operation to the argument UpdateBuilder. The argument name
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// should specify the item attribute to modify. The argument OperandBuilder
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// should specify the value to modify the the item attribute to. The resulting
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// UpdateBuilder can be used as an argument to the WithUpdate() method for the
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// Builder struct.
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//
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// Example:
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//
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// // Let update represent an already existing update expression. Set() adds
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// // the operation to to set the item attribute "itemToSet" to the value
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// // "setValue" if the item attribute does not exist yet. (conditional
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// // write)
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// update := update.Set(expression.Name("itemToSet"), expression.IfNotExists(expression.Name("itemToSet"), expression.Value("setValue")))
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//
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// // Adding more update methods
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// anotherUpdate := update.Remove(expression.Name("someName"))
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// // Creating a Builder
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// builder := Update(update)
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//
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// Expression Equivalent:
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//
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// Set(expression.Name("itemToSet"), expression.IfNotExists(expression.Name("itemToSet"), expression.Value("setValue")))
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// // Let :val be an ExpressionAttributeValue representing the value
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// // "setValue"
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// "SET itemToSet = :val"
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func (ub UpdateBuilder) Set(name NameBuilder, operandBuilder OperandBuilder) UpdateBuilder {
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if ub.operationList == nil {
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ub.operationList = map[operationMode][]operationBuilder{}
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}
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ub.operationList[setOperation] = append(ub.operationList[setOperation], operationBuilder{
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name: name,
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value: operandBuilder,
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mode: setOperation,
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})
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return ub
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}
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// buildTree builds a tree structure of exprNodes based on the tree
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// structure of the input UpdateBuilder's child UpdateBuilders/Operands.
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// buildTree() satisfies the TreeBuilder interface so ProjectionBuilder can be a
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// part of Expression struct.
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func (ub UpdateBuilder) buildTree() (exprNode, error) {
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if ub.operationList == nil {
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return exprNode{}, newUnsetParameterError("buildTree", "UpdateBuilder")
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}
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ret := exprNode{
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children: []exprNode{},
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}
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modes := modeList{}
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for mode := range ub.operationList {
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modes = append(modes, mode)
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}
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sort.Sort(modes)
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for _, key := range modes {
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ret.fmtExpr += string(key) + " $c\n"
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childNode, err := buildChildNodes(ub.operationList[key])
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if err != nil {
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return exprNode{}, err
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}
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ret.children = append(ret.children, childNode)
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}
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return ret, nil
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}
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// buildChildNodes creates the list of the child exprNodes.
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func buildChildNodes(operationBuilderList []operationBuilder) (exprNode, error) {
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if len(operationBuilderList) == 0 {
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return exprNode{}, fmt.Errorf("buildChildNodes error: operationBuilder list is empty")
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}
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node := exprNode{
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children: make([]exprNode, 0, len(operationBuilderList)),
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fmtExpr: "$c" + strings.Repeat(", $c", len(operationBuilderList)-1),
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}
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for _, val := range operationBuilderList {
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valNode, err := val.buildOperation()
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if err != nil {
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return exprNode{}, err
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}
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node.children = append(node.children, valNode)
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}
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return node, nil
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}
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