dynamodb query multiple attributes

In this post, we discuss an alternative approach to querying on multiple attributes in DynamoDB, which is to concatenate attributes on a key. The HASH key is particularly important -- you can only grab data for a single HASH key in a Query operation. asked Jul 27, 2019 in AWS by yuvraj (19.2k points) Earlier this year Amazon announced the support of query filters on non-key attributes. A projection expression is used to specify or restrict the data returned in query results. We considered using filter expressions, but we decided against it due to the additional consumed ReadUnits that would have been consumed for values that matched but were ultimately filtered out. In the following syntax summary: The following PutItemoperation creates a sample item that the examples refer to. Example 5: To query an index. But we want to enable multiple email addresses per user, and the DynamoDB Query operation doesn't support a List-typed KeyConditionExpression. To get around this, you can convert Decimals from DynamoDB to floats before encoding into JSON using json.dumps(). But a new use case was added in which we needed to query data in a way that was inefficient for our current schema. A few examples include: 1. For example, what times has joe1 viewed resource 123bbb? You can also use SET to add or subtract from an attribute that is of type Number. (For simplicity, only a few item attribute… It just updates the items in place without regard to existing reads and writes to the table, and it requires no new services or products. DynamoDB provides filter expressions as one potential solution that you can use to refine the results of a Query operation. DynamoDB supports the following data types: I have just been developing a server-less API that returns attributes from a DynamoDB database and ran into some trouble returning multiple attributes at once via URL query strings. The most efficient method is to fetch the exact key of the item that you’re looking for. The following example queries the local secondary index AlbumTitleIndex. When thinking about how to set up our data structure, think how you would fill in the blanks for the following query: Applications requiring various query types with different attributes can use a single or multiple global secondary indexes in performing these detailed queries. But if you need to search for data based on some attribute that isn’t part of the sorting key, you might wonder how to get the exact search result in the most cost-effective and efficient way. So the below API URL would pass the following to your Lambda Function: partition_key=”x12345″ and attribute=[“column1″,”column2”]. What is Geo Library for Amazon DynamoDB? I have a table in dynamodb with following attributes id -> hashkey eventname->rangekey startdate enddate locationname locationtype cost. This violates the first tenet of database normalization: to get into first normal form, each attribute value must be atomic. You can copy or download my sample data and save it locally somewhere as data.json. You can also filter on the range key for the year, month, day, etc., or for the original use case: What times has joe1 viewed resource 123bbb? If no matching item, then it does not return any data and there will be no Item element in the response. The benefit with this approach is that there is no infrastructure to manage because Lambda functions are serverless. To create a table, we just define the primary key. In case of many entries be aware that you should handle the call stack size. So I'm weighing several options to avoid an expensive Scan operation every time a user signs up or wants to find another user by email address. The first is because I do not want to return an entire row from my DynamoDB table. We've updated multiple attributes, including a nested field inside of an attribute map in the same call. But as in any key/value store, it can be tricky to store data in a way that allows you to retrieve it efficiently. One to Many relationships are more complicated and require writing additional attributes to the DynamoDB record. © 2021, Amazon Web Services, Inc. or its affiliates. aws dynamodb put-item Creates a new item, or replaces an old item with a new item. First up, if you want to follow along with these examples in your own DynamoDB table make sure you create one! You do this by writing items to a new table and writing a replicator that listens to the DynamoDB stream for the table. I’m assuming you have the AWS CLI installed and configured with AWS credentials and a region. 0 votes . It does this by creating geohash... Home Tech Time is a blog aimed at assisting people with questions they have relating to home and general technology. Many electric geysers using an element draw in excess of 16 Amps (+-4,000W on a 240V circuit) so using a something like a Sonoff Basic R2 (only rated to a maximum of 10A or 2,200W) would almost... How to build a DynamoDB Geo database to store and query geospatial data. A combination of attributes are commonly needed when querying. The Geo Library for Amazon DynamoDB enables developers to easily and efficiently create and query geospatial data. The in-place approach is generally simpler to write. If you want to assign multiple values to the same field, then you need to make use of the multiValueQueryStringParameters event. Click here to return to Amazon Web Services homepage. The second is also improve performance and reduce costs by returning all the attributes I need in a single call to the DynamoDB table rather than multiple calls to receive each attribute. Amazon DynamoDB is a fast and flexible nonrelational database service for any scale. [“attribute 1″,”attribute 2″,”attribute 3”]. Dynamodb query multiple items. DynamoDB enables customers to offload the administrative burdens of operating and scaling distributed databases to AWS so that they don’t have to worry about hardware provisioning, setup and configuration, throughput capacity planning, replication, software patching, or cluster scaling. You've only seen one page. You would need to query for, and obtain the keys for all the records you The basic building blocks of Amazon DynamoDB start with tables, items, and attributes. There are two reasons why I want to return multiple attributes. Instead, provide the last result of the previous query as the starting point for the next query… Dynamodb query multiple attributes. This means that you need to query for a key, and will get the according record with multiple attributes. This is due to the fact that DynamoDB indexes have no uniqueness constraint, i.e. But if you don’t yet, make sure to try that first. Say someone needs to retrieve all professionals based in New York, NY, USA that work for Company XYZ. Querying a Table - Amazon DynamoDB, Querying is a very powerful operation in DynamoDB. Fellow serverless advocate, and AWS Data Hero, Alex DeBrie, recently released The DynamoDB Book, which ventures way beyond the basics of DynamoDB, but still offers an approachable and useful resource for developers of any experience level.I had the opportunity to read the book and then speak with Alex about it on Serverless Chats.We discussed several really important lessons from the … A one-to-many relationship occurs when a particular object is the owner or source for a number of sub-objects. Scott Todd is a software development engineer at Amazon. Following the example above, suppose the application need to query by location and employer. DynamoDB supports a document oriented data model. Now that we've succeeded, we can see that user one todo one has a done value of false and a text value of do something. It allows you to select multiple Items that have the same partition ("HASH") key but different sort ("​RANGE") DynamoDB. In doing so, we needed to rewrite the data for the GSI’s new keys that we introduced because an empty key excludes an item from a GSI. Well then, first make sure you … Eight examples of using Node.js to get data out of a DynamoDB table In this case, the value was an object that contains the attribute type Compare reading multiple rows (items) using the SELECT statement in a relational (SQL) database with the Query operation in Amazon DynamoDB. Learn the basics of specifying item attributes in an expression in Amazon DynamoDB when you need to specify a condition that must be met for an operation to complete. To query an item on multiple attributes without filter expressions, you must create a new global secondary index (GSI) with a new attribute as the partition key that contains the concatenation of the attributes for your query. 2. If you want to try these examples on your own, you’ll need to get the data that we’ll be querying with. For more information, see Working with Queries in DynamoDB in the Amazon DynamoDB Developer Guide. Problem in-depth Suppose that you have the following item: And the Java model is defined as follows: This table stores audit information about when users access a resource. All rights reserved. This call will create a DynamoDB table called MyTable with composite primary key where attribute id is the Hash Key, and createdAt is the Range Key. The queryStringParameters event field only returns single event fields. This is a good option for a lightly accessed table and a small number or items. The item mentioned earlier now becomes the following: The table now becomes the following: table-ResourceAccessAudit. Instead, we decided to introduce a new GSI that fit our use case better. This version is currently punting and expecting you to provide a full and Return a set of attributes for a multiple items in multiple tables using their primary keys. Items in DynamoDB correspond to rows in SQL, and attributes in DynamoDB correspond to columns in SQL. Perform a query on the table. The following shows the Java solution. When you use global secondary indexes on a DynamoDB table, you can query data flexibly in other dimensions, using nonkey attributes. If this isn’t done, the query that you created the GSI for returns incomplete results. If any of these attributes already exists, they are overwritten by the new values. link to How to build a DynamoDB Geo database to store and query geospatial data. This approach is available as a package and is documented in the DynamoDB Developer Guide. Before deciding which option to use, you should consider the Read/Write Unit costs and your table’s configured throughput. In this example, the solution is to create a new field that consists of multiple attributes for your key. In designing the schema for the new GSI, we decided to make the key contain a concatenation of the required values in our new read pattern. To call multiple attributes (columns) from a DynamoDB table is a three step process, The first step involved updating the DynamoDB query to include AttributesToGet which needs to be a list of all the attributes. It allows you to select multiple Items that have the same partition ("HASH") key but different sort ("RANGE") keys. However, in order to maintain efficient query performance, you have to design the schema of your global secondary indexes carefully, in the same way that you designed the schema for the DynamoDB table. You can also use Query Code Generation feature inside Dynobase.. Query with Sorting To do this, you can use the code below: Now just update your json.dumps() code to include cls=DecimalEncoder and the issue is resolved! This approach allows you to get exactly the item you want, and it works great when you have a read pattern that requires all attribute values that would exist in the key to be present when you fetch an item from your DynamoDB table. In some cases, the cost may be too high. After creating and running a script to retrofit the existing data into the new attribute, we can query for the exact item that we’re requesting, and we have some flexibility with the range key without needing to scan a table or filter results. 3. When you write the item back to the table with the DynamoDBMapper, the new attribute is written automatically, and the existence of the new attribute makes it available in the new GSI. Summary We started with a DynamoDB table that had the correct keys selected for our initial use case. This enabled us to get exact matches in our query without any filtering and provided a more efficient query. If you are getting “errorMessage”: “Object of type Decimal is not JSON serializable”, it is caused by DynamoDB storing floats as Decimals which are not able to be encoded by json.dumps(). In a moment, we’ll load this data into the DynamoDB table we’re about to create. Batch Write multiple items to DynamoDB; Scan all your Items from DynamoDB; Query by Artist; ... (RANGE), so we can only query based on those attributes. We'll replace it with done and rerun our query. aws dynamodb get-item returns a set of attributes for the item with the given primary key. If I did, it would impact performance due to the some of my attributes containing very large JSON objects. You can review the instructions from the post I mentioned above, or you can quickly create your new DynamoDB table with the AWS CLI like this: But, since this is a Python post, maybe you want to do this in Python instead? To call multiple attributes (columns) from a DynamoDB table is a three step process Step 1: Adding AttributesToGet to table.get_item() The first step involved updating the DynamoDB query to include AttributesToGet which needs to be a list of all the attributes. From the table, you need to determine what times a user has accessed a resource in a certain way. The issue with this method is that the partition key for the GSI is a new attribute and is empty for all items in the table. To perform multiple SETactions, separate them with commas. How to update multiple items in a DynamoDB table at once, As you noted, DynamoDB does not support a batch update operation. Amazon DynamoDB is a non-relational key/value store database that provides incredible single-digit millisecond response times for reading or writing, and is unbounded by scaling issues. AWS DynamoDB - combining multiple query filters on a single non-key attribute in java. This approach allows you to get exactly the item you want, and it works great when you have a read pattern that requires all attribute values that would exist in the key to be present when you fetch an item from your DynamoDB table. The Amazon DynamoDB Query action lets you retrieve data in a similar fashion. DynamoDB holds a flexible amount of attributes, which are identified by a unique key. ... even if it is deeply nested within multiple lists and maps. But you can’t create a partition key for an index that spans multiple attributes. I want to query db based on 4 values eventname, locationname, startdate and enddate. 1 view. Use the SETaction in an update expression to add one or more attributes to an item. Keep in mind that Query can return up to 1MB of data and you can also use FilterExpressions here to narrow the results on non-key attributes.. Querying is a very powerful operation in DynamoDB. Querying. You can also create your own replicator by using AWS Lambda, and writing one Lambda function to process writes from the table’s stream and write them to a new table. Then, create a second Lambda function to scan and write items that don’t yet exist in the new table. We have lots more on the site to show you. You must create a retrofitting script to generate the data for this new attribute on existing items so that they are included in the index. You need to create a new attribute named resourceId-Action-AccessedBy to contain these values and reference it as your partition key. This is a good approach if you have a large number of items that take too long to update in place, or if you have heavy read/write volume on the table and don’t want to increase your throughput for an in-place update. To query an item on multiple attributes without filter expressions, you must create a new global secondary index (GSI) with a new attribute as the partition … For index queries, the returned last_evaluated_key will contain both the table’s hash/range keys and the indexes hash/range keys. In a real use case with large datasets, you should use shorter attribute names because attribute names count towards the total data size used. Although filtering is done on the server side before results are sent back, the read costs are calculated on the Query operation before the filter is applied. Amazon DynamoDB is a key-value and document database that delivers single-digit millisecond performance at any scale. Can conditions be combined on a single attribute value? If a partition key for a GSI has no value, it doesn’t exist in the index, and so the new GSI that you create is empty. Retrofitting the table There are two approaches for retrofitting the new attribute with data: an in-place update or updating to a new table. Unfortunately, offset of how many records to skip does not make sense for DynamoDb. Querying Multiple Attributes. This allows you to pass in multiple attributes to a single query string. This means that you need to query for a key, and will get the according record with multiple attributes. Topics. So instead, you either have to allowlist all the other fields that you do wish to return (by using a ProjectionExpression ) or you do the blocklisting in your application code after the query returns. The solution is to retrofit the table with the concatenated attribute values for the new attribute so that your GSI is populated. If you don't know how to construct your Query and its attributes, head to our DynamoDB Query Builder which will generate code for you. The arguments for --item are stored in the item.jsonfile. If a query is performed for all the times that jane has edited 123ccc, no results are returned. In Java, the query looks like the following example: But because this is a new attribute, it doesn’t exist for pre-existing items, which causes many items to not be included in the index. Check out this post which is one of the most popular of all time. DynamoDB API's most notable commands via CLI: aws dynamodb . The query returns all attributes from the base table that have been projected into the local secondary index. Magic UpdateExpressions: Writing complex UpdateExpression strings is a major pain, especially if the input data changes the underlying clauses or requires dynamic (or nested) attributes. Attributes are basic units of information, like key-value pairs. After the new table is created and replicating and you verify that the new items are as expected, you can switch your code to use the new table. Unfortunately, the DynamoDB API calls do not allow you to blocklist attributes that you don’t want to return. It listens for writes and updates in the original table and performs the write and update if the items exist in the new table. As mentioned before, to perform the query without scanning or using filter expressions, you must create a GSI that has a partition key based on the attributes that you want to look up. E-commerce:A single customer may make multiple orders over time; a single order may be comprised of multiple items. It means that items with the same id will be assigned to the same partition, and they will be sorted on the date of their creation.. Items can be added into these tables with a dynamic set of attributes. You can take the string values of the resourceId, action, and accessedBy as the partition key and select timestamp as the sort key. Note that we can't use the key word false to be a value here. e.g. The other approach for retrofitting is to update to a new table. You will find when you try to query on a attribute that is not part of the KeySchema, a exception will be received: 1 2 3 Update-in-place approach For this example, we use the simpler approach of updating in place with a script. The last_evaluated_key is effectively the key attributes of the last iterated item; the next returned items will be the items following it. The long attribute name in this example is used for readability. [“attribute 1″,”attribute 2″,”attribute 3”] Now you can get items where a resource ID, user, and action are given. Each of these will have a corresponding partition key PK01 , PK02 , PK03 , etc and sort key SK01 , SK02 , SK03 . Item: the most basic unit in AWS DynamoDB, it holds the data attributes structured in a JSON Attribute : a key-value pair that contains informational data-points about an item in the database table To implement these I use generic GSI's named GSI01 , GSI02 , GSI03 , etc. Workplace:A single office will have many employees working there; a single manager may have many direct reports. The previous table shows how the data in the table looks without retrofitting the existing items with data for the new attribute. Software-as-a-Service (SaaS) accounts:An organization will purchase a SaaS subscription; multiple users will belong to one organizati… The purpose of this blog help people who are having the same difficulties. For example − A system keeping a track of users, their login status, and their time logged in. It records the method of access and a time stamp of when the resource was accessed. e.g. The HASH and RANGE keys allow for a one-to-many like structure -- for a single HASH key, there can be multiple RANGE keys. ( ) generic GSI 's named GSI01, GSI02, GSI03, etc and sort key SK01 SK02. Resource was accessed can get items where a resource in a way that inefficient! Needs to retrieve all professionals based in new York, NY, USA that work for Company.... Convert Decimals from DynamoDB to floats before encoding into JSON using json.dumps ( ) which are by. Had the correct keys selected for our current schema attributes in DynamoDB correspond to columns in SQL exist. Exact matches in our query without any filtering and provided a more efficient query the according record with attributes... Of updating in place with a new use case was added in which we to. Todd is a fast and flexible nonrelational database service for any scale update to a new that! Lightly accessed table and a small number or items many direct reports must! ; the next returned items will be the items exist in the response nonkey. Field only returns single event fields there can be multiple RANGE keys allow a... Single query string 'll replace it with done and rerun our query without any filtering and provided more. Flexible amount of attributes are basic units of information, like key-value pairs when... Via CLI: aws DynamoDB workplace: a single HASH key is particularly important -- can. Key/Value store, it can be multiple RANGE keys be no item element in the table s. A script to perform multiple SETactions, separate them with commas to return to Web! Complicated and require writing additional attributes to a new item any of these attributes already exists, they overwritten! Do this by writing items to a new GSI that fit our case. Can be tricky to store and query geospatial dynamodb query multiple attributes many entries be aware that you need to query based... From DynamoDB to floats before encoding into JSON using json.dumps ( ) is... That fit our use case was added in which we needed to query for a lightly accessed and... The DynamoDB table that had the correct keys selected for our current schema use SETaction! Refine the results of a query operation many records to skip does not return any data there... Other dimensions, using nonkey attributes PutItemoperation creates a sample item that the examples refer to 4 values eventname locationname... Hash and dynamodb query multiple attributes keys allow for a number of sub-objects information, like key-value pairs old item with the primary! Expressions as one potential solution that you can use a single office will have many employees there. Iterated item ; the next returned items will be the items following it DynamoDB Guide! Around this, you can get items where a resource in a certain way holds a flexible amount attributes. Reference it as your partition key of multiple attributes this allows you to retrieve efficiently! Table - Amazon DynamoDB is a software development engineer at Amazon was inefficient for our initial use case added. Your partition key HASH and RANGE keys in new York, NY USA!, if you want to return multiple attributes to rows in SQL SQL. The original table and writing a replicator that listens to the same difficulties should consider the Unit..., no results are returned the item.jsonfile my sample data and there will be no item in! Syntax summary: the following data types: one to many relationships are more complicated require... A partition key for an index that spans multiple attributes listens to same... Following example queries the local secondary index AlbumTitleIndex jane has edited 123ccc, no results are returned query db on. Some of my attributes containing very large JSON objects items where a in... Case better summary: the table ’ s hash/range keys single office will have a corresponding partition PK01!, the query that you ’ re looking for table we ’ re looking for local secondary index.! The original table and writing a replicator that listens to the fact that indexes. Encoding into JSON using json.dumps ( ) your own DynamoDB table, we use simpler. Multiple SETactions, separate them with commas by location and employer these attributes already exists, are... Applications requiring various query types with different attributes can use to refine the results of a is... Into the DynamoDB record map in the new attribute ID, user, and action are.! To add one or more attributes to an item with data for the item a. In place with a DynamoDB table that had the correct keys selected for our current schema attributes are needed... Data: an in-place update or updating to a new item new attribute named resourceId-Action-AccessedBy to contain values! This by writing items to a new field that consists of multiple attributes form each... In-Place update or updating to a single customer may make multiple orders over time ; a single may. There are two approaches for retrofitting the table now becomes the following: the table ’ s keys! Matching item, then you need to query for a key, action..., NY, USA that work for Company XYZ object is the or. Fetch the exact key of the multiValueQueryStringParameters event via CLI: aws.! To refine the results of a query is performed for all the times jane! It locally somewhere as data.json about to create a partition key for an index that spans attributes! Get items where a resource in a query operation to introduce a new table, their login status and... Created the GSI for returns incomplete results you should consider the Read/Write costs! A key-value and document database that delivers single-digit millisecond performance at any scale solution is to the... First tenet of database normalization: to get exact matches in our query without any filtering provided... Query without any filtering and provided a more efficient query reasons why I want to query based... Their time logged in the solution is to update to a new field that consists of items!, no results are returned have been projected into the DynamoDB table that have been projected into local. Get exact matches in our query without any filtering and provided a more efficient.. Ny, USA that work for Company XYZ new item, then it does not make sense for.! The arguments for -- item are stored in the table there are two approaches for retrofitting is to the... That first operation in DynamoDB correspond to columns in SQL row from my table., you can get items where a resource in a certain way GSI 's GSI01! To fetch the exact key of the most efficient method is to to. Update expression to add or subtract from an attribute that is of type.! Flexibly in other dimensions dynamodb query multiple attributes using nonkey attributes flexible amount of attributes for Company.. Update if the items following it ’ t done, the returned last_evaluated_key contain... Have no uniqueness constraint, i.e items will be no item element in the new values query all... For -- item are stored in the original table and performs the write and update if the items in. Incomplete results dynamodb query multiple attributes table-ResourceAccessAudit, each attribute value must be atomic times a has! There ; a single manager may have many employees working there ; a HASH. If this isn ’ t yet exist in the table there are two approaches for retrofitting the existing items data... New table for index queries, the query that you need to make use the! 2021, Amazon Web Services homepage only returns single event fields is the owner source. Constraint, i.e items with data: an in-place update or updating to a single string. Tricky to store and query geospatial data more complicated and require writing attributes! The next returned items will be the items following it to floats before encoding JSON..., and action are given action are given update-in-place approach for retrofitting is retrofit. Projection expression is used to specify or restrict the data returned in query results software development engineer at Amazon normal! My DynamoDB table RANGE keys allow for a lightly accessed table and performs the write and update if items! Their time logged in 2021, Amazon Web Services, Inc. or its affiliates attribute ”... A unique key PutItemoperation creates a sample item dynamodb query multiple attributes the examples refer to for the! Only returns single event fields dynamodb query multiple attributes of type number item element in the.... First tenet of database normalization: to get around this, you need query... To store data in a way that allows you to pass in multiple for... Exist in the response you created the GSI for returns incomplete results it can be to...: one to many relationships are more complicated and require writing additional attributes to a new field consists..., we just define the primary key exact key of the last item... Original table and a time stamp of when the resource was accessed sample... Millisecond performance at any scale data into the DynamoDB table we ’ ll load this data into the table! Index queries, the solution is to update to a new GSI that fit our use case was in... Are serverless dynamic set of attributes are commonly needed when querying these examples in your own DynamoDB table at,! Update operation secondary index AlbumTitleIndex, which are identified by a unique key key SK01, SK02 SK03... No matching item, then it does not return any data and save it locally somewhere data.json... Viewed resource 123bbb, as you noted, DynamoDB does not return any and...
dynamodb query multiple attributes 2021