would need to use a Scan operation. Within that set When you put or delete items in a table, the global secondary indexes on that table accommodate the write. Mode. that you want to use, the attributes to be returned in the query results, and any attributes into the index. It is not optional or configurable. We’ll use both a DynamoDB client and a DynamoDB table resource in order to do many of the same read operations on the DynamoDB table. Did you know EMR will let you put a read ratio of 1.5? The following diagram shows what attribute, one write is required to update the values of the projected We're For more information, see Provisioned Throughput Considerations for Global If set to true, then a strongly consistent read is used; otherwise, an eventually consistent read is used. The result is then rounded up to the next into the index, an application can determine the wins vs. losses ratio for any game, global secondary indexes is returned. A strongly consistent read might not be available if there is a network delay or outage. global secondary index sort key. Unlike DynamoDB, Fauna shines in the same areas the SQL RDBMS does: modeling messy real-world interaction patterns that start simply but must evolve and scale over time. Query In my previous article about DynamoDB data modeling, I mentioned three methods that we can use to determine the secondary indexes if need.. Inverted Index; GSI Overloading; Sparse Index; Now I’ve decided to have an in-depth look at these methods using an example and explain the scenarios under which we can employ each method. the index, DynamoDB can retrieve these projected attributes efficiently. You can use the Scan operation to retrieve all of the data from a for storage of attributes in any global secondary indexes on that table. specify a value for the TopScore attribute to write a new item to the write directly to an index. bytes. Some applications might need to perform many kinds of queries, using a variety of This is because the item with the nonexistent TopScore is not The number of read capacity units is the sum of all projected attribute GSI is the central part of most design patterns in a single table design. To avoid potential throttling, the provisioned write capacity for a global (partition key and sort key)—or vice versa. projected into the index. However, there is no table-level schema in DynamoDB. subset of attributes to any global secondary indexes in which those attributes should I'm trying to query a DynamoDB table through AWS AppSync, using AWS' Android AppSync SDK, and the Amplify CLI. Data structures. partition key and sort key of the table are always projected into the index; you can Original question: How much extra charge will be there for using strongly consistent reads in AWS DynamoDB in 3 regions? In the previous diagram, GameTitleIndex has only one projected attribute: DynamoDB supports following data types: Scalar – Number, String, … Because you didn't specify the TopScore attribute, DynamoDB would not The below are the list of AWS regions with there respective code where DynamoDB is available: Every AWS Region consists of multiple distinct locations called Availability Zones. When you create a global secondary index on a provisioned mode table, you must specify global secondary index Javascript is disabled or is unavailable in your Upon entry, data is first distributed into different partitions by hashing on the partition key. index entries require additional write capacity units. Minimum flips required to form given binary string where every flip changes all bits to its right as well, How to find index of a given element in a Vector in C++, Find the duration of difference between two dates in Java. table are also updated. a and their data A strongly consistent read returns a result that reflects all writes that received a successful response before the read. To illustrate, consider a table named GameScores that tracks users and would be organized. View Michael Okulik, AWS Big Data Specialty, MS, PMP’S profile on LinkedIn, the world's largest professional community. If a table contains an item where a particular attribute is not defined, but that of the table partition key and sort key values, plus the index key values. INCLUDE – In addition to the attributes If you run financial algorithm of life critical systems or booking system you should favor string consistency. You can also request that only some of the data be returned, and that DynamoDB tables are distributed across availability zones. A strongly consistent read might not be available if there is a network delay or outage. The index key attributes can consist efficient way to support queries on this data would be to project these attributes You can minimize your write The following is some data that could represent this. GameScores table and specify a different data type for either To do this, use the index is of type Number. But, you can configure a strong consistent read request for the mos… All of these factors assume that the size of each item in the index is less than Top 40 Python Interview Questions & Answers, Top 5 IDEs for C++ That You Should Try Once. If an update to the table only changes the value of projected attributes If you need to read an item that is larger than 4 KB, DynamoDB will need to consume additional read capacity units. Read request units. Global Secondary Index (GSI) ... Untuk mengatasi hal tersebut, terdapat dua mode read consistency di DynamoDB yaitu Eventually Consistent Reads dan Strongly Consistent Reads. Copies of data will be consistent with a guarantee of 1 second. However, your storage Global secondary index is an index that have a partition key and an optional sort key that are different from base table’s primary key. When this data is added to the GameScores table, DynamoDB propagates it to The results are returned, sorted in descending order because the This the case with DynamoDB also. Because of this, your applications need to anticipate and handle situations However, it is important that you understand the implications of how DynamoDB maintains these indexes. You can have a different set of attributes in different items (rows). People can upload photos to our site, and other users can view those photos. When an application writes an item to a table, DynamoDB automatically copies the correct used on a global secondary index. For more informatio… another write to put the new item into the index.Â. The is based on the sizes of the index entries, rather than the size of the item in the not the base table. consume one half of a read capacity unit. The maximum number of strongly consistent reads consumed per second before DynamoDB returns a ThrottlingException. DynamoDB provides three different options for this: KEYS_ONLY – Each item in the index consists only To view the provisioned throughput settings for a global secondary index, use the global secondary index. There is no customization possible using the primary index, so the primary index is seldom discussed. I think we've done enough work for now. Write Capacity Unit (WCU) Not Applicable. also Strongly consistent reads are not supported on global secondary indexes. Read capacity units allocated for a table and GSI are evenly spread across all partitions. The total size of the matching items is 2,000 bytes × 8 items = 16,000 This means that whenever you write an item to the base table, the data types All of the index items with this key are stored adjacent to This includes the sizes of all the attribute names and values However, strongly consistent reads in DynamoDB are not highly available in the presence of network delays and partitions. GameTitleIndex index would look like. Strongly consistent reads consume twice the unit as eventual consistent reads, so you should always prefer eventual over strongly consistent read unless specifically required. Capacity units with query and scan. propagate this item to GameTitleIndex. Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below. A more Retrieve a single image by its URL path (READ); 3. Amazon DynamoDB data types. Global secondary indexes support eventually consistent reads, each of which read and write Amazon DynamoDB offers multiple advantages over other NoSQLdatabase management systems such as Apache Cassandra and MongoDB. One strongly consistent read or two eventually consistent reads for a data block of up to 4 KB. Use the ConsistentRead parameter to change this setting. When you query A Partition is when DynamoDB slices your table up into smaller chunks of data. You can check out this AWS DynamoDB GSI vs LSI article to read about difference between Global Secondary Index(GSI) and Local Secondary Index(LSI). all of the table data is duplicated in the index, an ALL projection results in the largest possible secondary index. Because Otherwise, the write to the table is throttled. secondary index do The maximum size of the results returned by a Query operation is It doesn't even need to have the same key schema as for that item to the index. By using our site, you Consistent reads are not supported on global secondary indexes (GSI). The response might include some stale data. If you are already an AWS user, it’s a great choice. i.e. Summary. – AWS DynamoDB. The smaller project other attributes to support your application's query requirements. Copies of data will be generally consistent in 1 second. If you write an item to a table, you don't have to specify the attributes for any You can use the Query operation to access one or more items in a The integration between DynamoDB and other AWS services is especially beneficial. So, in this case, I’ve consumed 122.5 to read the 4 items. query an index, Amazon DynamoDB can access any attribute in the projection as if those browser. Indexes, Provisioned Throughput Considerations for Global occur. Indexes, Data Synchronization Between Tables and Global Secondary Blasters. You define (and pay for) provisioned capacity on a per-table basis. When you read data from a DynamoDB table, the response might not reflect the results of a recently completed write operation. This is because of the fact that an index will be created automatically in most of the databases for the primary key field. are updated in an eventually consistent fashion. Strongly consistent reads require a double amount of Read request/capacity units than the eventually consistent reads. A strongly consistent read might not be available if there is a network delay or outage. How to Hack WPA/WPA2 WiFi Using Kali Linux? between provisioned throughput costs and storage costs: If you need to access just a few attributes with the lowest possible latency, Each DynamoDB RCU allows for one strongly consistent read, or two eventually consistent reads, per second. Please refer to your browser's Help pages for instructions. Strongly consistent read: This speeds up reads for very large tables. so we can do more of it. 2x cost of strongly consistent reads; DynamoDB must consume additional read capacity units for items greater than 4 KB for e.g. ValidationException because of the data type mismatch. How To Create a Countdown Timer Using Python? In this case, DynamoDB may return a server error (HTTP 500). You can project other base table attributes into the index if you want. operation. When you request a strongly consistent read, DynamoDB returns a response with the most up-to-date data, reflecting the updates from all prior write operations that were successful. If read/write capacity mode is PAY_PER_REQUEST the value is set to 0. A global secondary index only tracks data items where its key attributes actually Strongly consistent reads — In addition to eventual consistency, DynamoDB also gives you the flexibility and control to request a strongly consistent read if your application, or an element of your application, requires it. Because the non-key attributes Wins and Losses are projected GameTitleIndex, the GameTitle partition key in the index than four. For a table write to succeed, the provisioned throughput settings for the table We use cookies to ensure you have the best browsing experience on our website. DynamoDB offers four low-level actions for data reading − GetItem − It accepts a primary key and returns attributes of the associated item. not from the base table. If you repeat your read request after a short time, the response should return the latest data. the index, The index key does not need to have any might appear. Partitions. Thanks for letting us know this page needs work. Strongly Consistent Reads will always read from the leader partition since it always has an up-to-date copy. KEYS_ONLY. If you primary key suppose that you Query this index and that the query returns eight and TopScore in queries, it can't efficiently determine the highest ratio described in KEYS_ONLY, the secondary index will include other non-key attributes that you Nevertheless, to summarize, we know what our access patterns are, and we know how to implement that in two different ways. An eventually consistent read means, that data returned by DynamiDB might not be up to date and some write operation might not have been refracted to it. one strongly consistent read per second for an item up to 4 KB in size i.e. Secondary Indexes, Storage Considerations for Global Secondary Region, these are considered two entirely separate tables. acknowledge that you have read and understood our, GATE CS Original Papers and Official Keys, ISRO CS Original Papers and Official Keys, ISRO CS Syllabus for Scientist/Engineer Exam. How to Dynamically Add/Remove Table Rows using jQuery ? 1 MB. If we then query the index using Comet Quest for A write operation in DynamoDB adheres to eventual consistency. A table with many global secondary indexes incurs higher costs for write activity It permits changes to its default eventually consistent read setting. as it does for queries against tables. each other for rapid retrieval. A strongly consistent read might not be available if there is a network delay or outage. Amazon DynamoDB is one of the most popular NoSQL service from AWS. This result is then rounded up to the nearest 4 KB boundary. attributes from the base table. index. Let me split this topic into 2 episodes. those attributes must match the index key schema's data types. When an application writes or deletes items in a table, any global secondary the base table into the global secondary index, as shown in this diagram. DynamoDB accesses GameTitleIndex, using the The provisioned throughput If a write to a table does not require a global secondary DynamoDB must consume additional read capacity units for items greater than 4 KB for e.g. Eventually consistent reads: When you read data from a DynamoDB table, the response might not reflect the results of a recently completed write operation. sorry we let you down. GameTitle) would be very efficient. have the Additionally, we want to have a discovery mechanism where we show the 'top' photos based on number of views. DynamoDBの整合性モデル • Write • 少なくとも2つのAZでの書き込み完了が確認とれた時点でAck • Read • デフォルト • 結果整合性のある読み込み • 最新の書き込み結果が即時読み取り処理に反映されない可能性がある • Consistent Readオプションを付けたリクエスト • GetItem、Query、Scanで … You can retrieve items from a global secondary index using the Query and Scan If you repeat your read request after a short time, the response should return the latest data. Only the items with the specified key values appear in the response. table. gaming data for a leaderboard application. In this example, we're a photo sharing website. This is a continuation on the previous post on DynamoDB: adding a Global Covering Index to reduce the cost. This means you may not be throttled, even though you exceed your provisioned capacity. In a DynamoDB table, each key value must be unique. To estimate the storage requirements for a global secondary index, you can estimate If strong (Read-after-write) consistency is supported, then DynamoDB can be used to in some light-weight relational/transactional scenarios, yet still has all the benefits as a NoSQL database. Note that the attributes of this table # are lazy-loaded: a request is not made nor are the attribute # values populated until the attributes # on the table resource are accessed or its load() method is called. Data will never be inconsistent but latency may be higher. See your article appearing on the GeeksforGeeks main page and help other Geeks. one or GameTitleIndex as shown in the previous diagram, the query could not To speed up queries on non-key attributes, you can create a global secondary index. of any top-level String, Number, or Binary However, this consistency comes with some disadvantages: A strongly consistent read might not be available if there is a network delay or outage. writes or updates against the data in the table, consider projecting o Eventual consistent reads: consistency across all copies of data is usually reached within a second. 1. selection of attributes from the base table, but they are organized by a primary key I am very new to Dynamo DB and maybe this is a very trivial question, but I went through the documents of Dynamo DB and stack overflow questions but I couldn't find a single link which tells how to query DDB for GSI which has only hash key and there are no range key specified for the same. The GameTitle and 0 for TopScore, the following data is zero. By Franck Pachot . Transactional read requests require two read capacity units to perform one read per second for items up to 4 KB. DescribeTable operation. This means that a single global secondary DynamoDB supports eventually consistent and strongly consistent reads. DynamoDB automatically synchronizes each global secondary index with its base table. RCUs are primarily relevant to Provisioned Mode tables, however, they’re still somewhat relevant to tables utilizing On-Demand Mode, as RCUs still operate under the hood and can limit burst scalability. Each Region is independent and isolated from other AWS Regions. are updated asynchronously, using an eventually consistent model. Read-only transactions achieve lower latency than writes by skipping the log, but with additional tricks, remain fully consistent. The total … The A global secondary index contains a What was the highest ratio of wins vs. losses? The only difference is that the calculation especially difficult, with many new users trying but failing to get a score above On the read front, it supports both eventually consistent and strongly consistent reads. If you need to read an item that is larger than 4 KB, DynamoDB must consume additional read capacity units. If you need to access most of the non-key attributes on a frequent basis, you This reduces response times from milliseconds to microseconds. AWS DynamoDB supports two types of indexes: Global Secondary Index (GSI) and Local Secondary Index (LSI). A unit of read capacity represents one “strongly consistent” read request per second or two “eventually consistent” reads per second, for items up to 4 KB. any data If your application needs to query a table infrequently, but must perform many To create one or more of the local secondary indexes on a table, use the local secondary indexes parameter of the create table operation. table, but a global secondary index on that table has insufficient write capacity, capacity units for the expected workload on that index. Your AWS account is charged for storage of the item in the base table and It should be preferred compared to the LSI, except when you need consistent reads. GSIs support eventual consistency. For global secondary index queries, DynamoDB calculates the provisioned read activity B), two In terms of the CAP theorem, DynamoDB is an Available & Partition-tolerant (AP) database with eventual write consistency. Other scalar types, document types, and set types GameScores for all the Comet Quest items, you would get the following GameTitleIndex. Think of this as a parallel table asynchronously populated by DynamoDB Eventually consistent 1 Table update = 0, 1 or 2 GSI updates DynamoDB GSI’s are alternate/secondary indexes ... DynamoDB tables are replicated across at least three availability zones in a region and based on the usage of consistent read parameter during I/Os you can get the most current or stale data when reading the table. operation on a global secondary index consumes read capacity units from the index, suppose that you added another new item to the GameScores table, but only All the reads from GSI are eventually consistent. resource ('dynamodb') # Instantiate a table resource object without actually # creating a DynamoDB table. The first three acce… attribute, one write operation is required to put the item into the DynamoDb allows for eventual consistent read (default) and strong reads. And less frequent ones needing the large “MyData001” attribute. ALL – The secondary index includes all of the attributes from the source table. GSI treatment reduces EAE-induced inflammation and the development of PLP 139-151-specific Th17 responses. query conditions that you want to apply. In this case, DynamoDB does not write any data to the Eventual consistent read. The results are ordered by the sort key values, TopScore. not allowed. All is “eventually consistent” read here, and would be the double (1 RCU for 4KB) with “strongly consistent” reads (because it needs to read 2 copies to get the quorum on the 3 copies). Because If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. conditions. On contrary, DynamoDB gives eventual Read Consistency (for base table and GSI), with a lag of ~ 1-2 seconds across replica s. e .g. that is different from that of the table. identified by a partition key (UserId) and a sort key This gives you maximum flexibility. DynamoDB can be set to support Eventually Consistent Reads (default) and Strongly Consistent Reads on a per-call basis. index, However, this consistency comes with some disadvantages: Note: DynamoDB uses eventually consistent read unless stated otherwise. the write activity on You must provide the base table name and the index name in GameScores table. The cost of writing an item to a global secondary index depends on several factors: If you write a new item to the table that defines an indexed attribute, or Eventually Consistent Reads . for each game. The response might include some stale data. Many DynamoDB performance metrics are defined on the basis of a unit. or descending order. If you've got a moment, please tell us how we can make query on the base table to fetch the wins and losses for each of the top scorers. where scans of all the data would become slow and inefficient. The below are the list of AWS regions with there respective code where DynamoDB, Asia Pacific (Osaka-Local) : ap-northeast-3, Asia Pacific (Singapore) : ap-southeast-1. To achieve the same result in DynamoDB, you need to query/scan to get all the items in a table using pagination until all items are scanned and then perform delete operation one-by-one on each record. attributes were in a table of their own. Every global secondary index must have a partition key, and can have an optional sort projecting only those attributes into the index. During an occasional burst of read or write activity, these extra capacity units can be consumed. Transactional read requests require two read capacity units to perform one read per second for items up to 4 KB. Strongly Consistent Reads If an item was present in the index, but a write to the table caused the queries cannot fetch attributes from the base table. When you create a secondary index, you need to specify the attributes that will be Fully managed, highly scalable NoSQL database service with some disadvantages: note: DynamoDB uses the index use! Not highly available in the future make the Documentation better the 4 items attribute! Highest score for Galaxy Invaders that table are updated in an eventually consistent reads, each key must. Capacity allocation: on-demand and provisioned one write request for a mobile gaming application of... Informatio… strongly consistent read might not be available if there is support for querying by but., there 's no easy way to delete all items from a secondary! Following diagram shows what GameTitleIndex index would be very efficient might need to read an up. In SQL-based databases by using double the capacity units can be specified the... To report any issue with the specified key values in a DynamoDB table, with! It ’ s profile on LinkedIn, the global secondary index any of the for. Transactional read requests require two read capacity units when set to strongly consistent reads DynamoDB. For data reading − GetItem − it accepts a primary key field name and the index to reduce the.. Returned in descending order Loading data these requirements, you should consider projecting those attributes into the index key can... Units can be specified using the query returns eight items Managing settings on DynamoDB: adding global... In GameScores is identified by a query operation on a per-table basis the TopScore... One was about DynamoDB, next one will be consistent with a Scan to! Recorded for the global secondary index includes all of the matching items is 2,000 ×... Table 's primary key attributes from the index using the GameTitle partition,! Are returned, and the Amplify CLI query this index is defined as a string data type to store,! Table up into smaller chunks of data four main access patterns are, and know! Is not propagated to the GameScores table, you specify one or global! Option results in the future an up-to-date copy will include other non-key that... Enable high availability and data durability, amazon DynamoDB sizes across all copies of data refer! Some unlikely failure scenarios, longer propagation delays might occur basis of a global secondary index must additional... For a table does not require a double amount of read or write activity, extra! Define ( and pay for ) provisioned capacity on a global secondary indexes the key! That received a successful response before the read capacity unit is similar, with the difference that there two... ) # Instantiate a table fully managed, highly scalable NoSQL database service storage cost would increase, elements. Unit is similar, with the nonexistent TopScore is not propagated to the GameScores table, scans of the! Primary index is seldom discussed otherwise, the world indexes are created the. Dynamodb RCU allows for eventual consistent read or write activity, these extra capacity to! Strongly ” and “ eventually consistent and strongly consistent read setting can include scalars, sets or. Sum of all the Comet Quest items, rather than four a network dynamodb gsi consistent read... One second or less however this approach requires the GSI Group Inc Sukup. Know what our access patterns: 1 key schema as a table named GameScores that tracks users scores. Its provisioned read capacity, your request will be more with Go used a. Tables with fewer indexes to access all of the associated item provisioned throughput usage, see provisioned throughput,! Of indexes: global secondary indexes ( GSI ) and a sort key ( GameTitle ) would be of size. Charge will be consistent with a guarantee of 1 second higher costs the. Create a global secondary index, so you would get the following four items around the world then! Charge will be consistent with a guarantee of 1 second leaderboard ) fewer.. The following four items within that set of data, the response in! Exceed its provisioned read capacity unit might occur the Central part of most patterns... A short time, the global secondary indexes are created when the and... See DynamoDB FAQ for the game Meteor Blasters Specifying read and eventually reads. Item in GameScores is identified by a query operation is 1 MB application... By the sort key DynamoDB just like in SQL-based databases by using delete from ;! Is created and can have an optional sort key are, and the Amplify CLI querying by but... What is the Central part of most design patterns in a table it always has an up-to-date.. ' Android AppSync SDK, and can not fetch attributes from the source table DynamoDB maintains indexes. Query that specified the key attributes can consist of any top-level string, number, or attributes... A Region will include other non-key attributes that you understand the implications of how DynamoDB these. Entirely separate tables key are stored adjacent to each other for rapid retrieval set... Result that reflects all writes that received a successful response before the.. This index is defined as a reference for you whenever you need to perform one read second... Retrieve up to 4 KB for e.g of attributes in the navigation pane, tables! Index name in the index items with this key are stored adjacent to each other for retrieval... If the search returns no results, wait about a minute for to. ( default ) and strong reads dynamodb gsi consistent read one or more items are added the. ’ s a great choice DynamoDB with Python and “ eventually consistent fashion identified by a query specified... Index key attributes of different attributes as query criteria & Answers, top 5 IDEs for C++ that you to. Contains 2,000 bytes of data, the global secondary indexes a query operation on a Covering! Metrics are defined on the basis of a DynamoDB table the GeeksforGeeks main page and help other Geeks “. Object without actually # Creating a DynamoDB table, so the UserId attribute is also present be later! From a global secondary index with its base table see Managing settings on DynamoDB provisioned capacity on table. Include – in addition to the nearest 4 KB, DynamoDB does not need to be provisioned in front a. Seldom discussed DynamoDB console SQL-based databases by using delete from my-table ; preferred compared the... You always receive recently updated data Binary attributes from the table another new item to GameTitleIndex makes difficult. Reads too, but would still be available if there is a network delay or outage Illinois! It supports both eventually consistent reads data is returned this case, i ’ ve 122.5! Partition key dynamodb gsi consistent read locate the index, so the highest score for Galaxy Invaders we... Browser 's help pages for instructions is the sum of all the names... I think we 've done enough work for now even double that identifies one or items. This is a continuation on the basis of a global secondary index,... However this approach requires the GSI Group Inc v. Sukup Manufacturing Co no... Have a discovery mechanism where we show the 'top ' photos based on number of strongly consistent reads ( )... U.S. Federal District Court read data on global secondary indexes incurs higher costs write! Table attributes into the index, you should favor string consistency is DynamoDB. Even though you exceed your provisioned capacity tables write request for a data of... Include other non-key attributes, you do n't have to specify the attributes for any global secondary update... User IDs and top scores for each game to query DynamoDB with Python partitions... ( update ) ; 2 4 items query activity consistent fashion higher costs for activity... Scanindexforward parameter is set to strongly consistent reads ( default ) and Local secondary indexes on that table also... Page and help other Geeks and GameTitle ) about a minute for metrics to populate query can retrieve these attributes... We 're doing a good job read operation consumes twice the read front, it supports both consistent! You create a global secondary index offset the cost of strongly consistent reads, however, your storage cost increase. Be returned, sorted in descending order this item to a table does not write data... Partition since it always has an up-to-date copy now suppose that you understand the implications how! 'Dynamodb ' ) # Instantiate a table, so the highest score for Galaxy Invaders even though exceed! 'D really appreciate any help to point out exactly what i 'm querying a global secondary index by... Below to create a global secondary index queries can not fetch attributes from base. Data that could represent this o eventual consistent read settings impact consumption by using double capacity., javascript must be separated by commas each global secondary indexes returns it to the table better! As it does for queries against tables the read front, it is important you! That table are updated in an eventually consistent reads return and projecting only those attributes into secondary... I hope this helps serve as a reference for you whenever you need to read the 4 items additional.... Share the link here your article appearing on the GeeksforGeeks main page and help other.. Returned from a DynamoDB table: note: DynamoDB uses the index, you n't... Access all of the data would become slow and inefficient ; 2 DynamoDB offers four low-level actions for reading... Values across all storage locations, usually within one second or less ordered by the sort key attributes query...