for some reason I want to use book.randomID as key in amazon DynamoDB table using java code. when i tried id added a new field in the item named "book.randomID"
List<KeySchemaElement> keySchema = new ArrayList<KeySchemaElement>();
keySchema.add(new KeySchemaElement().withAttributeName("conceptDetailInfo.conceptId").withKeyType(KeyType.HASH)); // Partition
and here is the json structure
{
"_id":"123",
"book":{
"chapters":{
"chapterList":[
{
"_id":"11310674",
"preferred":true,
"name":"1993"
}
],
"count":1
},
"randomID":"1234"
}
}
so is it possible to use such element as key. if yes how can we use it as key
When creating DynamoDB tables AWS limits it to the types String, Binary and Number. Your attribute book.random seems to be a String.
As long as it's not one of the other data types like List, Map or Set you should be fine.
Just going to AWS console and trying it out worked for me:
Related
I'm unable to filter dynamodb map in AWS console
Querying with mapper contains "A" works. structure of mapper is
"mapper": [
"\"A\"",
"\"B\"",
{
"bar": "foo"
}
]
How can I filter {"bar":"foo"}.
I tried
contains {"bar":"foo"}
contains '{"bar":"foo"}'
contains {bar:foo}
But none works. Please suggest.
If the mapper list is reliably ordered, the console's PartiQL editor can filter records containing {"bar": "foo"} at index 2:
select * from myTable where mapper[2].bar = 'foo'
Note: This is technically a scan operation. You can make it a query by adding WHERE conditions for your primary key.
I have a DynamoDB table:
+--------------------------------------------------+
| Customer ID (Primary Key)|Gamestats (JSON entry) |
+--------------------------------------------------+
JSON:
{
"Gamestats": [
{
"ID": "QuickShootingMode",
"status": 1
},
{
"ID": "FastReloadMode", // Just want to update this and not update the entire JSON
"status": 0
}
],
"CustomerID": "xyz"
}
I want to update only parts of the JSON. What is the best way to do it? Eg, update the QuickShootingMode to be false.
One way is to make a call and fetch the JSON and then Iterate the JSON and update the value and then put the new JSON back in dynamo DB. It means it would make 2 calls
A) to get the data and
B) to put the data in DB.
Is there a better way by which I could directly update the data and avoid making these extra network calls? I could convert each key of the JSON to be a column in dynamo BD, but if the number of keys grows then I’ll end up having lots of column (which might be a bad design), hence I think having the JSON saved in one column Game stats would make more sense.
Map<String, AttributeValue> key = new HashMap<>();
AmazonDynamoDB dynamoDB = dynamoDBClient.getDynamoDB();
key.put(USER_ID_KEY, new AttributeValue().withS("xyz"));
key.put("Gamedata", new AttributeValue().withS("some JSON"));
PutItemRequest request = new PutItemRequest()
.withTableName(table)
.withItem(key);
PutItemResult result = dynamoDB.putItem(request);
Is there a better way to achieve what I want?
It looks like from your question you are storing stringified JSON. If so an update won't help you, but as far as I can tell there is no value in storing stringified JSON instead of using dynamodb maps and lists.
You can use an update to set a nested attribute in a map or a list. Using a map instead of a list for the gamestats attribute is better because then you don't have to worry about the order of the attributes.
Javascript example with Gamestats being a map.
dynamodb.update({
TableName: table,
Key: key,
UpdateExpression: 'SET #gs.#qs.#status = :newStatus',
ExpressionAttributeNames: {'#gs': 'Gamestats', '#qs': 'QuickShootingMode', '#status': 'status' },
ExpressionAttributeValues: { ':newStatus': false }
}, callback)
I am fairly new in this realm and any help is appreciated
I have a table in Dynamodb database named Tenant as below:
"TenantId" is the hash primary key and I have no other keys. And I have a field named "IsDeleted" which is boolean
Table Structure
I am trying to run a query to get the record with specified "TenantId" while it is not deleted ("IsDeleted == 0")
I can get a correct result by running the following code: (returns 0 item)
var filter = new QueryFilter("TenantId", QueryOperator.Equal, "2235ed82-41ec-42b2-bd1c-d94fba2cf9cc");
filter.AddCondition("IsDeleted", QueryOperator.Equal, 0);
var dbTenant = await
_genericRepository.FromQueryAsync(new QueryOperationConfig
{
Filter = filter
}).GetRemainingAsync();
But no luck when I try to get it with following code snippet (It returns the item which is also deleted) (returns 1 item)
var queryFilter = new List<ScanCondition>();
var scanCondition = new ScanCondition("IsDeleted", ScanOperator.Equal, new object[]{0});
queryFilter.Add(scanCondition);
var dbTenant2 = await
_genericRepository.LoadAsync("2235ed82-41ec-42b2-bd1c-d94fba2cf9cc", new DynamoDBOperationConfig
{
QueryFilter = queryFilter,
ConditionalOperator = ConditionalOperatorValues.And
});
Any Idea why ScanCondition has no effect?
Later I also tried this: (throw exception)
var dbTenant2 = await
_genericRepository.QueryAsync("2235ed82-41ec-42b2-bd1c-d94fba2cf9cc", new DynamoDBOperationConfig()
{
QueryFilter = new List<ScanCondition>()
{
new ScanCondition("IsDeleted", ScanOperator.Equal, 0)
}
}).GetRemainingAsync();
It throws with: "Message": "Must have one range key or a GSI index defined for the table Tenants"
Why does it complain about Range key or Index? I'm calling
public AsyncSearch<T> QueryAsync<T>(object hashKeyValue, DynamoDBOperationConfig operationConfig = null);
You simply cant query a table only giving a single primary key (only hash key). Because there is one and only one item for that primary key. The result of the Query would be that still that single item, which is actually Load operation not Query. You can only query if you have composite primary key in this case (Hash (TenantID) and Range Key) or GSI (which doesn't impose key uniqueness therefore accepts duplicate keys on index).
The second code attempts to filter the Load. DynamoDBOperationConfig's QueryFilter has a description ...
// Summary:
// Query filter for the Query operation operation. Evaluates the query results and
// returns only the matching values. If you specify more than one condition, then
// by default all of the conditions must evaluate to true. To match only some conditions,
// set ConditionalOperator to Or. Note: Conditions must be against non-key properties.
So works only with Query operations
Edit: So after reading your comments on this...
I dont think there conditional expressions are for read operations. AWS documents indicates they are for put or update operations. However, not being entirely sure on this since I never needed to do a conditional Load. There is no such thing like CheckIfExists functionality as well in general. You have to read the item and see if it exists. Conditional load will still consume read throughput so your only advantage would be only NOT retrieving it in other words saving the bandwith (which is very negligible for single item).
My suggestion is read it and filter it in your application layer. Dont query for it. However what you can also do is if you very need it you can use TenantId as hashkey and isDeleted for range key. If you do so, you always have to query when you wanna get a tenant. With the query you can set rangeKey(isDeleted) to 0 or 1. This isnt how I would do it. As I said, would just read it and filter it at my application.
Another suggestion thing could be setting a GSI on isDeleted field and writing null when it is 0. This way you can only see that attribute in your table when its only 1. GSI on such attribute is called sparse index. Later if you need to get all the tenants that are deleted (isDeleted=1) you can simply scan that entire index without conditions. When you are writing null when its 0 dynamoDB wont put it in the index at the first place.
I am writing an app using the Realm.io database that will pull data from another, server database. The server database has some tables whose primary keys are composed of more than one field. Right now I can't find a way to specify a multiple column key in realm, since the primaryKey() function only returns a String optional.
This one works:
//index
override static func primaryKey() ->String?
{
return "login"
}
But what I would need looks like this:
//index
override static func primaryKey() ->[String]?
{
return ["key_column1","key_column2"]
}
I can't find anything on the docs on how to do this.
Supplying multiple properties as the primary key isn't possible in Realm. At the moment, you can only specify one.
Could you potentially use the information in those two columns to create a single unique value that you could use instead?
It's not natively supported but there is a decent workaround. You can add another property that holds the compound key and make that property the primary key.
Check out this conversation on github for more details https://github.com/realm/realm-cocoa/issues/1192
You can do this, conceptually, by using hash method drived from two or more fields.
Let's assume that these two fields 'name' and 'lastname' are used as multiple primary keys. Here is a sample pseudo code:
StudentSchema = {
name: 'student',
primaryKey: 'pk',
properties: {
pk: 'string',
name: 'string',
lastname: 'string',
schoolno: 'int'
}
};
...
...
// Create a hash string drived from related fields. Before creating hash combine the fields in order.
myname="Uranus";
mylastname="SUN";
myschoolno=345;
hash_pk = Hash( Concat(myname, mylastname ) ); /* Hash(myname + mylastname) */
// Create a student object
realm.create('student',{pk:hash_pk,name:myname,lastname:mylastname,schoolno: myschoolno});
If ObjectId is necessary then goto Convert string to ObjectID in MongoDB
Cassandra support updating specific value in Collection by syntax
ALTER TABLE users ADD todo map<timestamp, text>
UPDATE users SET todo['2012-10-2 12:00'] = 'throw my precious into mount doom'
WHERE user_id = 'frodo';
http://www.datastax.com/documentation/cql/3.0/cql/cql_using/use_map_t.html
Did not see any example of using QueryBuilder to update specific row in Map. How it can be done?
I think you have several options.
1/ Build your own query based on the CQL one.
Example: Consider that you have a table named Interactions and in your schema a column of type named 'attributes'.
String update ="UPDATE demo.Interactions SET attributes=attributes + {'i':'j'} where id='ff';
SimpleStatement statement = new SimpleStatement(update);
session.execute(statement);
2/ Use Java API.
Java API is not that documented indeed.
Let's take an example
a- Create an update object using queryBuilder
Update update = QueryBuilder.update(keyspace, tableName);
b- Then populate with 'put' or 'putAll' functions. put/putAll will add/update content
update.with(QueryBuilder.putAll(key, map));
To remove a key, set the content of a key to null, like:
for (Object item : map.keySet()) {
update.with(
QueryBuilder.put(columName, item, null)
);
}
Then execute the query.
Following methods are available for different types:
LIST:
QueryBuilder.appendAll(...)
QueryBuilder.discardAll(...)
SET:
QueryBuilder.addAll(...)
QueryBuilder.removeAll(...)
MAP:
QueryBuilder.putAll(...)
QueryBuilder.put(...)
The list is not exhautive.
Have a look in QueryBuilder class if you do not find what you are looking for.
Best regards and best luck with Cassandra.