$util.transform contains helper methods that make it easier to perform
complex operations against data sources, such as
Amazon DynamoDB
filter operations.
$util.transform.toDynamoDBFilterExpression(Map) :
Map
Converts an input string to a filter expression for use with
DynamoDB.
Input:
$util.transform.toDynamoDBFilterExpression({
"title":{
"contains":"Hello World"
}
})
Output:
{
"expression" : "contains(#title, :title_contains)"
"expressionNames" : {
"#title" : "title",
},
"expressionValues" : {
":title_contains" : { "S" : "Hello World" }
},
}
$util.transform.toElasticsearchQueryDSL(Map) :
Map
Converts the given input into its equivalent OpenSearch Query DSL expression, returning
it as a JSON string.
Input:
$util.transform.toElasticsearchQueryDSL({
"upvotes":{
"ne":15,
"range":[
10,
20
]
},
"title":{
"eq":"hihihi",
"wildcard":"h*i"
}
})
Output:
{
"bool":{
"must":[
{
"bool":{
"must":[
{
"bool":{
"must_not":{
"term":{
"upvotes":15
}
}
}
},
{
"range":{
"upvotes":{
"gte":10,
"lte":20
}
}
}
]
}
},
{
"bool":{
"must":[
{
"term":{
"title":"hihihi"
}
},
{
"wildcard":{
"title":"h*i"
}
}
]
}
}
]
}
}
The default
operator
is assumed to be AND.
$util.transform.toSubscriptionFilter(Map) :
Map
Converts a Map input object to a SubscriptionFilter expression
object. The $util.transform.toSubscriptionFilter method is used as an input to
the $extensions.setSubscriptionFilter() extension. For more information, see
Extensions.
$util.transform.toSubscriptionFilter(Map, List) :
Map
Converts a Map input object to a SubscriptionFilter expression
object. The $util.transform.toSubscriptionFilter method is used as an input to
the $extensions.setSubscriptionFilter() extension. For more information, see
Extensions.
The first argument is the Map input object that's converted to the
SubscriptionFilter expression object.
The
second argument is a List of field names that
are
ignored in the first Map input object while constructing the
SubscriptionFilter expression object.
$util.transform.toSubscriptionFilter(Map, List, Map) :
Map
Converts a
Map input object to a SubscriptionFilter expression object. The
$util.transform.toSubscriptionFilter method is used as an input to the
$extensions.setSubscriptionFilter() extension. For more information, see
Extensions.
The first argument is the Map input object that's converted to the
SubscriptionFilter expression object, the second argument is a
List of field names that will be ignored in the first Map
input object, and the third argument is a Map input object of strict rules
that's included while constructing the SubscriptionFilter expression object.
These strict rules are included in the SubscriptionFilter expression object in
such a way that at least one of the rules will be satisfied to pass the subscription
filter.
The
following table
explains
the how the arguments of the following utilities are defined:
-
$util.transform.toSubscriptionFilter(Map) : Map
-
$util.transform.toSubscriptionFilter(Map, List) : Map
-
$util.transform.toSubscriptionFilter(Map, List, Map) : Map
- Argument 1: Map
-
Argument
1
is a Map object with the following key values:
For field names as keys, the conditions on these fields' entries are in the
form of "operator" : "value".
The following example shows how entries can be added to the
Map:
"field_name" : {
"operator1" : value
}
## We can have multiple conditions for the same field_name:
"field_name" : {
"operator1" : value
"operator2" : value
.
.
.
}
When a field has two or more conditions on it, all of these conditions are
considered to
use
the OR operation.
The input Map can also have "and" and "or" as keys, implying that
all entries within these should be joined using AND or OR logic depending on the
key. The key values "and" and "or" expect an array of conditions.
"and" : [
{
"field_name1" : {
"operator1" : value
}
},
{
"field_name2" : {
"operator1" : value
}
},
.
.
].
Note that
you
can
nest
"and" and "or".
That is,
you
can have nested "and"/"or" within another "and"/"or" block. However, this
doesn't
work for simple fields.
"and" : [
{
"field_name1" : {
"operator" : value
}
},
{
"or" : [
{
"field_name2" : {
"operator" : value
}
},
{
"field_name3" : {
"operator" : value
}
}
].
The following example shows an input of argument
1 using $util.transform.toSubscriptionFilter(Map) :
Map.
Input(s)
Argument 1: Map:
{
"percentageUp": {
"lte": 50,
"gte": 20
},
"and": [
{
"title": {
"ne": "Book1"
}
},
{
"downvotes": {
"gt": 2000
}
}
],
"or": [
{
"author": {
"eq": "Admin"
}
},
{
"isPublished": {
"eq": false
}
}
]
}
Output
The result is a Map object:
{
"filterGroup": [
{
"filters": [
{
"fieldName": "percentageUp",
"operator": "lte",
"value": 50
},
{
"fieldName": "title",
"operator": "ne",
"value": "Book1"
},
{
"fieldName": "downvotes",
"operator": "gt",
"value": 2000
},
{
"fieldName": "author",
"operator": "eq",
"value": "Admin"
}
]
},
{
"filters": [
{
"fieldName": "percentageUp",
"operator": "lte",
"value": 50
},
{
"fieldName": "title",
"operator": "ne",
"value": "Book1"
},
{
"fieldName": "downvotes",
"operator": "gt",
"value": 2000
},
{
"fieldName": "isPublished",
"operator": "eq",
"value": false
}
]
},
{
"filters": [
{
"fieldName": "percentageUp",
"operator": "gte",
"value": 20
},
{
"fieldName": "title",
"operator": "ne",
"value": "Book1"
},
{
"fieldName": "downvotes",
"operator": "gt",
"value": 2000
},
{
"fieldName": "author",
"operator": "eq",
"value": "Admin"
}
]
},
{
"filters": [
{
"fieldName": "percentageUp",
"operator": "gte",
"value": 20
},
{
"fieldName": "title",
"operator": "ne",
"value": "Book1"
},
{
"fieldName": "downvotes",
"operator": "gt",
"value": 2000
},
{
"fieldName": "isPublished",
"operator": "eq",
"value": false
}
]
}
]
}
- Argument 2: List
-
Argument
2
contains a List of field names that shouldn't be considered in the
input Map
(argument
1)
while constructing the SubscriptionFilter expression object. The
List can also be empty.
The following example shows the inputs of
argument
1
and argument
2
using $util.transform.toSubscriptionFilter(Map, List) : Map.
Input(s)
Argument 1: Map:
{
"percentageUp": {
"lte": 50,
"gte": 20
},
"and": [
{
"title": {
"ne": "Book1"
}
},
{
"downvotes": {
"gt": 20
}
}
],
"or": [
{
"author": {
"eq": "Admin"
}
},
{
"isPublished": {
"eq": false
}
}
]
}
Argument 2: List:
["percentageUp", "author"]
Output
The result is a Map object:
{
"filterGroup": [
{
"filters": [
{
"fieldName": "title",
"operator": "ne",
"value": "Book1"
},
{
"fieldName": "downvotes",
"operator": "gt",
"value": 20
},
{
"fieldName": "isPublished",
"operator": "eq",
"value": false
}
]
}
]
}
- Argument 3: Map
-
Argument
3
is a Map object
that
has field names as key values (cannot have "and" or "or"). For field names as
keys, the conditions on these fields are entries in the form of "operator" :
"value". Unlike
argument
1,
argument
3
cannot have multiple conditions in the same key. In addition,
argument
3
doesn't have an "and" or "or" clause, so there's no nesting involved
either.
Argument
3
represents a list of strict rules, which are added to the
SubscriptionFilter expression object
so
that at least one of these conditions
is
met to pass the filter.
{
"fieldname1": {
"operator": value
},
"fieldname2": {
"operator": value
}
}
.
.
.
The following example shows the inputs of argument
1, argument 2, and argument 3 using
$util.transform.toSubscriptionFilter(Map, List, Map) : Map.
Input(s)
Argument 1: Map:
{
"percentageUp": {
"lte": 50,
"gte": 20
},
"and": [
{
"title": {
"ne": "Book1"
}
},
{
"downvotes": {
"lt": 20
}
}
],
"or": [
{
"author": {
"eq": "Admin"
}
},
{
"isPublished": {
"eq": false
}
}
]
}
Argument 2: List:
["percentageUp", "author"]
Argument 3: Map:
{
"upvotes": {
"gte": 250
},
"author": {
"eq": "Person1"
}
}
Output
The result is a Map object:
{
"filterGroup": [
{
"filters": [
{
"fieldName": "title",
"operator": "ne",
"value": "Book1"
},
{
"fieldName": "downvotes",
"operator": "gt",
"value": 20
},
{
"fieldName": "isPublished",
"operator": "eq",
"value": false
},
{
"fieldName": "upvotes",
"operator": "gte",
"value": 250
}
]
},
{
"filters": [
{
"fieldName": "title",
"operator": "ne",
"value": "Book1"
},
{
"fieldName": "downvotes",
"operator": "gt",
"value": 20
},
{
"fieldName": "isPublished",
"operator": "eq",
"value": false
},
{
"fieldName": "author",
"operator": "eq",
"value": "Person1"
}
]
}
]
}
