15.1 Querying Collection
When querying data from a collection, you can use a set of constraints to filter objects.
To filter, you need to specify a set of conditions (filters if you like).
We use YAML for the request format.
Conditions
- Field: operation
Type: string
Description: Each condition must contain an operation field
---
- Field: Condition body
Description: Depending on the selected operation, the set of fields may vary
Operations
This section lists all the operations that you can use in the conditions.
- Operation: and
Fields: conditions
Type: []Condition
Description: Contains a set of conditions
---
- Operation: or
Fields: conditions
Type: []Condition
Description: Contains a set of conditions
---
- Operation: equal
Fields: query, expected
Type: Expression
Description: query: Expression for calculating the value,
expected: Expression for calculating the expected value
---
- Operation: not_equal
Fields: query, expected
Type: Expression
Description: query: Expression for calculating the value,
expected: Expression for calculating the expected value
---
- Operation: has_keys
Fields: keys
Type: []string
Description: Set of paths to check for availability
---
- Operation: not_has_keys
Fields: keys
Type: []string
Description: Set of paths to check for unavailability
Expressions
This section lists all the expressions that you can use in the conditions.
- Expression: Field
Field: field
Type: string
Description: This extension allows you to get the value of a record field in its entirety.
Below you can see the available values for this extension:
• object_id
• value
• created_at
---
- Expression: Path
Field: path
Description: This extension allows you to look inside an object value.
To view nested values, use the dot separator.
Examples:
• a
• a.b
• a.b.c
---
- Expression: Value
Field: value
Type: string, number, array, object, bool
Description: This extension allows you to specify a specific value for further comparison
Filtering examples
All examples will be carried out based on the following input data.
[
{
"storage_id": "c9d6b296-ab57-435e-a28b-6b207b9674b8",
"collection_name": "users",
"object_id": "8f842609-b710-479b-96d3-0b0f3be62571",
"value": {
"name": "Marta",
"age": 35,
"info": {
"verified": true
},
"labels": [
"author",
"reader"
]
},
"created_at": "2006-01-02 15:04:05.999999999 -0700 MST"
},
{
"storage_id": "c9d6b296-ab57-435e-a28b-6b207b9674b8",
"collection_name": "users",
"object_id": "88c90cbe-6aab-43dd-81cb-e7a37580e813",
"value": {
"name": "Joe",
"age": 40,
"info": {
"verified": false,
"banned": true
},
"labels": [
"reader",
"critic"
]
},
"created_at": "2006-01-02 15:04:05.999999999 -0700 MST"
}
]
Basic Filter
First, let's find a match by path in object value. For this we will need the operator equal.
operation: equal
query:
path: name
expected:
value: Marta
This will return all the objects where the field name is equal to Marta.
{
"storage_id": "c9d6b296-ab57-435e-a28b-6b207b9674b8",
"collection_name": "users",
"object_id": "8f842609-b710-479b-96d3-0b0f3be62571",
"value": {
"name": "Marta",
"age": 35,
"info": {
"verified": true
},
"labels": [
"author",
"reader"
]
},
"created_at": "2006-01-02 15:04:05.999999999 -0700 MST"
}
Now let's find all users whose name is not Marta. For this we will need the operator not_equal.
operation: not_equal
query:
path: name
expected:
value: Marta
This will return all the objects where the field name is not equal to Marta. In our case, we will get an object with the user Joe.
{
"storage_id": "c9d6b296-ab57-435e-a28b-6b207b9674b8",
"collection_name": "users",
"object_id": "88c90cbe-6aab-43dd-81cb-e7a37580e813",
"value": {
"name": "Joe",
"age": 40,
"info": {
"verified": false,
"banned": true
},
"labels": [
"reader",
"critic"
]
},
"created_at": "2006-01-02 15:04:05.999999999 -0700 MST"
}
Now let's request all users with a complete match of a part of the object.
operation: equal
query:
path: info
expected:
value:
verified: false
banned: true
The value expression automatically determines the value type (string, object, list, number).
In this case, we will again get the user object Joe.
{
"storage_id": "c9d6b296-ab57-435e-a28b-6b207b9674b8",
"collection_name": "users",
"object_id": "88c90cbe-6aab-43dd-81cb-e7a37580e813",
"value": {
"name": "Joe",
"age": 40,
"info": {
"verified": false,
"banned": true
},
"labels": [
"critic"
]
},
"created_at": "2006-01-02 15:04:05.999999999 -0700 MST"
}
Multiple Filters
Filtering with OR
operation: or
conditions:
- operation: equal
query:
path: info.banned
expected:
value:true
- operation: equal
query:
path: info.verified
expected:
value:false
Filtering with AND
operation: and
conditions:
- operation: equal
query:
path: info.banned
expected:
value:true
- operation: equal
query:
path: info.verified
expected:
value:false
Nested Filters
You can nest conditions within each other to get the best filtering result.
operation: and
conditions:
- operation: equal
query:
path: age
expected:
value: 40
- operation: or
conditions:
- operation: equa;
query:
path: info.verified
expected:
value:false
- operation: equal
query:
path: info.banned
expected:
value:true
Search for complex objects
Sometimes you may want to find an object where the fields of the object are somehow related to each other.
In this case, you can use two Path expressions and compare their values with each other.
operation: equal
query:
path:
path: first_name
expected:
path: last_name
In this example, if someone specifies the same first and last name, we will get such users in the response.
You can also combine different types of expressions in one query.
operation: and
conditions:
- operation: equal
query:
path: first_name
expected:
path: last_name
- operation: not_equal
query:
path: first_name
expected:
path: Joe