I'm currently trying to create a dynamic query using AppSync and Apache Velocity Template Language (VTL).
I want to evaluate series of begins_with with "OR"
Such as:
{
"operation": "Query",
"query": {
"expression": "pk = :pk and (begins_with(sk,:sk) or begins_with(sk, :sk1)",
"expressionValues": {
":pk": { "S": "tenant:${context.args.tenantId}",
":sk": {"S": "my-sort-key-${context.args.evidenceId[0]}"},
":sk1": {"S": "my-sort-key-${context.args.evidenceId[1]}"}
}
}
But that isn't working. I've also tried using | instead of or but it hasn't worked either. I get:
Invalid KeyConditionExpression: Syntax error; token: "|", near: ") | begins_with" (Service: AmazonDynamoDBv2;
How can I achieve this using VTL?
Original answer
you're missing a closing parenthesis after the begins_with(sk, :sk1). That is, the third line should be:
"expression": "pk = :pk and (begins_with(sk,:sk) or begins_with(sk, :sk1))"
I just ran the fixed expression and it worked as expected.
Revised
Actually, there are subtleties.
the or operator can be used in filter-expression but not in key-condition-expressions. For instance, a = :v1 and (b = :v2 or b = :v3) will work as long as a and b are "regular" attributes. If a and b are the table's primary key (partition key, sort key) then DDB will reject the query.
Reading this answer seems that this isn't possible, as DynamoDB only accepts a single Sort key value and a single operation.
There's also no "OR" condition in the operation:
https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_Query.html#DDB-Query-request-KeyConditionExpression
If you also want to provide a condition for the sort key, it must be combined using AND with the condition for the sort key. Following is an example, using the = comparison operator for the sort key:
I am going to be restructuring the access pattern to better match my request.
Related
I have a DynamoDB table, I need to find the records which are between the given date range.
So here is my table structure
{
"Id":"String",
"Name":"String",
"CrawledAt":"String"
}
In this table partition key as Id and CrawledAt fileds used. And also created local secondary index with CrawledAt field and it's name "CrawledAt-index"
When querying most of the articles using Id with CreatedAt. But in my case I don't know what is the Id, I only need to retrieve records for a particular date range.
Here is the code I have tried
request = {
"TableName": "sflnd00001-test",
"IndexName": "CrawledAt-index",
"ConsistentRead": False,
"ProjectionExpression": "Name",
"KeyConditionExpression":
"CrawledAt between :v_start and :v_end",
"ExpressionAttributeValues": {
":v_start": {"S": "2020-01-31T00:00:00.000Z"},
":v_end": {"S": "2025-11-31T00:00:00.000Z"} }
}
response = table.query(**request)
It's returning this error
"An error occurred (ValidationException) when calling the Query operation: Invalid KeyConditionExpression: Incorrect operand type for operator or function; operator or function: BETWEEN, operand type: M",
Can someone please tell me how to find data set with the given date range without providing primary key
You cannot do a between or any other function on a partition key, you must always provide the entire key.
For your use-case your GSI partition key should be a single value, and the crawledAt should be the sort key.
{
"Id":"String",
"Name":"String",
"CrawledAt":"String",
"GsiPk": "Number"
}
.
"KeyConditionExpression":
"GsiPk = 1 AND CrawledAt between :v_start and :v_end"
This would then allow you to retrieve all the data in the table between two dates. But be aware of the caveat of doing this, using a single value for a GSIPK is not scalable, and would cap the write requests to approx 1000WCU.
If you need more scale you can assign a random number to the GSIPK (n) to increase the number of partitions which would then require you to make (n) queries to collect all the data.
Alternatively you can Scan the table and use FilterExpression which is also not a scalable solution:
aws dynamodb scan \
--table-name MusicCollection \
--filter-expression "timestamp between :a and :b" \
--expression-attribute-names file://expression-attribute-names.json \
--expression-attribute-values file://expression-attribute-values.json
Is there any way of supplying multiple values for a DynamoDB table's Sort Key whilst doing a query in Boto3?
For a single SK value to search on, I'm doing this:
table.query(
IndexName="my_gsi",
KeyConditionExpression=Key('my_gsi_pk').eq({pk value}) & Key('my_gsi_sk').eq({sk value}),
FilterExpression={filter expression}
)
... which works.
However, my scenario involves searching on one of a couple of potential SK values, so I'd like to, in SQL terms, do something like this:
WHERE my_gsi_pk = {pk value}
AND my_gsi_sk IN ({sk value 1}, {sk value 2})
I've looked in the Boto3 documentation in the .query() section and concentrated upon the KeyConditionExpression syntax but can't identify whether this is possible or not.
The query API does not support the IN operator in the KeyConditionExpression.
Use the execute_statement API instead. This executes a PartiQL statement, which does accept the IN operator in query operations for the Partition and Sort keys:
sk = ["Foo", "Bar"]
res = client.execute_statement(
Statement=f'SELECT * FROM "my_table"."my_gsi" WHERE my_gsi_pk = ? AND my_gsi_sk IN [{",".join(["?" for k in sk])}]',
Parameters= [{"S": "1"}] + [{"S": k} for k in sk]
)
This creates a PartiQL Statement like SELECT * FROM "my_table"."my_gsi" WHERE my_gsi_pk = ? AND my_gsi_sk IN [?, ?] and substitution Parameters like [{"S": "1"}, {"S": "Foo"}, {"S": "Bar"}].
Please note that the PartiQL will spend much more RCU than the Query. You can check this by requesting ReturnConsumedCapacity = ReturnConsumedCapacity.TOTAL
I have a Users table, with key {id: hash, email: range} and I want to create an user only if no user with the same email exists. I am trying to use a transaction, so I think I need to use a condition:
case Dynamo.transact_write_items([
{
:condition_check,
{
table_name(),
%{id: user_id, email: email},
condition_expression: "email <> :email",
expression_attribute_values: [email: email]
}
},
{
:put,
{
table_name(),
new_user
}
}
])
|> ExAws.request() do
{:ok, _} -> {:ok, new_user}
{:error, _} -> {:error, "unable to create user"}
end
This is not working, and I have the following questions:
in the key argument, in the condition, I have to specify: %{id: user_id, email: email}, but I have to specify user_id, which still does not exist, I have only generated it. How can I define a key with no value ?
I am having the following error: Transaction request cannot include multiple operations on one item, so I suppose that, given the way I have defined the key in the condition, it counts either the check and the put as two operations on the same entity. How can I check the existence of an entity in a consistent way (and so in a transaction) ?
The Elixir code here is of course not relevant, that's just the language I am using :)
According to the doc, no two actions can target the same item when using transaction. I don't think this is what you are looking for.
You can however, use conditional checks in regular operations. From the doc for instance,
aws dynamodb update-item \
--table-name ProductCatalog \
--key '{"Id": {"N": "456"}}' \
--update-expression "SET Price = Price - :discount" \
--condition-expression "Price > :limit" \
--expression-attribute-values file://values.json
will do the following:
get item with given ID
read the price and checks the condition against it
update accordingly if the condition is met
If the condition is not met, then the query will fail with a specific code.
note that update is actually an upsert
You must know beforehand the ID of the item you are looking for (actually, you must know the hash key. It could be an ID, a username, or whathever you have chosen)
Also, note that this is a unique query that is thus completely concurrent-safe.
CURRENTLY
I have a table in DynamoDB with a single attribute - Primary Key - that contains unique values.
PK
------
#A#B#C#
#B#C#
#C#D#E#
#BC#
ISSUE
I am looking to do 2 searches for #B#C# (1) exact match, and (2) containing match, and therefore only want results:
(1) Exact Match:
#B#C#
(2) Containing Match:
#A#B#C#
#B#C#
Are these 2 searches possible against the primary key?
If so, what is the most efficient query to run? e.g. QUERY or SCAN
Note:
For (2) I am using the following code, but it is returning all items in DB:
params = {
TableName: 'myTable',
FilterExpression: "contains(#key, :v)",
ExpressionAttributeNames: { "#key": "PK" },
ExpressionAttributeValues: { ":v": #B#C# }
}
dynamodb.scan(params,callback)
DynamoDB supports two main types of searches: query and scan. The Query operation finds items based on primary key values. The Scan operation returns one or more items and item attributes by accessing every item in a table or a secondary index
If you wanted to find the item with a primary key #B#C, you would use the query API:
ddbClient.query(
{
"TableName": "<YOUR TABLE NAME>",
"KeyConditionExpression": "#pk = :pk",
"ExpressionAttributeValues": {
":pk": {
"S": "#B#C"
}
},
"ExpressionAttributeNames": {
"#pk": "PK"
}
}
)
For your second access pattern, you'll need to use the scan API because you are searching across the entire table/secondary index.
You can use scan to test if a primary key has a substring using contains. I don't see anything wrong with the format of your scan operation.
Be careful when using scan this way. Because scan will read your entire table to fetch results, you will have a fairly inefficient operation at scale. If this operation is run infrequently, or you are running it against a sparse index, it's probably fine. However, if it's one of your primary access patterns, you may want to reconsider using the scan API for this operation.
I am having trouble using AWS Boto3 to query DynamoDB with a hash key and a range key at the same time using the recommend KeyConditionExpression. I have attached an example query:
import boto3
from boto3 import dynamodb
from boto3.session import Session
dynamodb_session = Session(aws_access_key_id=AWS_KEY,
aws_secret_access_key=AWS_PASS,
region_name=DYNAMODB_REGION)
dynamodb = dynamodb_session.resource('dynamodb')
table=dynamodb.Table(TABLE_NAME)
request = {
'ExpressionAttributeNames': {
'#n0': 'hash_key',
'#n1': 'range_key'
},
'ExpressionAttributeValues': {
':v0': {'S': MY_HASH_KEY},
':v1': {'N': GT_RANGE_KEY}
},
'KeyConditionExpression': '(#n0 = :v0) AND (#n1 > :v1)',
'TableName': TABLE_NAME
}
response = table.query(**request)
When I run this against a table with the following scheme:
Table Name: TABLE_NAME
Primary Hash Key: hash_key (String)
Primary Range Key: range_key (Number)
I get the following error and I cannot understand why:
ClientError: An error occurred (ValidationException) when calling the Query operation: Invalid KeyConditionExpression: Incorrect operand type for operator or function; operator or function: >, operand type: M
From my understanding the type M would be a map or dictionary type and I am using a type N which is a number type and matches my table scheme for the range key. If someone could explain why this error is happening or I am also open to a different way of accomplishing the same query even if you cannot explain why this error exists.
The Boto 3 SDK constructs a Condition Expression for you when you use the Key and Attr functions imported from boto3.dynamodb.conditions:
response = table.query(
KeyConditionExpression=Key('hash_key').eq(hash_value) & Key('range_key').eq(range_key_value)
)
Reference: Step 4: Query and Scan the Data
Hope it helps
Adding this solution as the accepted answer did not address why the query used did not work.
TLDR: Using query on a Table resource in boto3 has subtle differences as opposed to using client.query(...) and requires a different syntax.
The syntax is valid for a query on a client, but not on a Table. The ExpressionAttributeValues on a table do not require you to specify the data type. Also if you are executing a query on a Table resource you do not have to specify the TableName again.
Working solution:
from boto3.session import Session
dynamodb_session = Session(aws_access_key_id=AWS_KEY,aws_secret_access_key=AWS_PASS,region_name=DYNAMODB_REGION)
dynamodb = dynamodb_session.resource('dynamodb')
table = dynamodb.Table(TABLE_NAME)
request = {
'ExpressionAttributeNames': {
'#n0': 'hash_key',
'#n1': 'range_key'
},
'ExpressionAttributeValues': {
':v0': MY_HASH_KEY,
':v1': GT_RANGE_KEY
},
'KeyConditionExpression': '(#n0 = :v0) AND (#n1 > :v1)',
}
response = table.query(**request)
I am the author of a package called botoful which might be useful to avoid dealing with these complexities. The code using botoful will be as follows:
import boto3
from botoful import Query
client = boto3.Session(
aws_access_key_id=AWS_KEY,
aws_secret_access_key=AWS_PASS,
region_name=DYNAMODB_REGION
).client('dynamodb')
results = (
Query(TABLE_NAME)
.key(hash_key=MY_HASH_KEY, range_key__gt=GT_RANGE_KEY)
.execute(client)
)
print(results.items)