sharding vs partitioning. Partitioning and Sharding in PostgreSQL are good features. sharding vs partitioning

 
Partitioning and Sharding in PostgreSQL are good featuressharding vs partitioning  A database can be split vertically — storing different tables & columns in a separate database or horizontally — storing rows of a same table in multiple database nodes

The consumers need some sort of ordering guarantee. For stateless services, you can think about a partition being a logical unit. 0:00. Conclusion. Sharding is useful to increase performance, reducing the hit and memory load on any one resource. A partition is a division of a logical database or its constituent elements into distinct independent parts. partitioning. Sharding involves splitting and distributing one logical data set across. Sharding Key: A sharding key is a column of the database to be sharded. Sharding key is only. Here, each partition is known as a shard and holds a specific subset of the data, such as all the orders for a specific set of. We’re using the partitioning. In horizontal partitioning, also called sharding, each partition holds data for a subset of the total data set. Sharding is a special case of data partitioning, where the partitions are distributed across different servers or clusters, called shards. The activation sharding specs are applied as in the initial example: we just with_sharding_constraint. You can partition your data using 2 main strategies: on the one hand you can use a table column, and on the other, you can use the data time of ingestion. This initial. To illustrate, let’s say you have a database that stores information about all the products. Sharding is almost replication's antithesis, though they are orthogonal concepts and work well together. When you use Solr, Sitecore does not handle the sharding. database-design. By contrast, sharding offers unlimited scalability. Partitioning works best when the cardinality of the partitioning field is not too high. Version 10 of PostgreSQL added the declarative table partitioning feature. Sharding implies breaking up the data across physical machines. The only difference is that in transaction sharding, the partitioning and creation of shards are done based on the transactions. Lookup based partitioning: It uses a lookup table which helps in redirecting to different tables/node base on given input fields. For others, tools and middleware are available to assist in sharding. Partitioning or sharding during data extraction requires some best practices to be followed. Comparison of database sharding and partitioning. You want to concentrate data for efficiency of storage and/or indexing. European customers vs. You need to make subsequent reads for the partition key against each of the 10 shards. This key is responsible for partitioning the data. 2. Partitioning — Splitting up a large monolithic database into multiple smaller databases based on data cohesion. Both sharding and partitioning mean distributing data into smaller and. Horizontal partitioning or sharding. Choose a scheme that matches the data characteristics and query patterns, and avoid schemes that cause. This defeats the purpose of sharding/partitioning. In the third method, to determine the shard. It's not a choice of one or the other, since the two techniques are not mutually exclusive. sharding is a bit of a false dichotomy. e. All data fits in-memory. Some data within a database remains present in all shards, [a] but some appear only in a single shard. This is where horizontal partitioning comes into play. We achieve horizontal scalability through sharding”. I am happy to discuss any of the above in more detail, but only in a more focused context. Here the data is divided based on a shard key onto a separate database server instance. Union views might provide the full original table view. Kinesis Data Streams segregates the data records belonging to a stream into multiple shards. Sharding -- only if you need to 1000 writes per second. On the other hand, data partitioning is when the database is. Data is not only read but is partially processed on the remote servers (to the extent that this. Add a comment. U think dbms can support this. entity id, the same approach applies . 이 두 가지 기술은 모두 거대한 데이터셋을. "Plain" MongoDB use sharding instead, and you can set up a document property that should be used as a delimiter for how your data should be sharded. You can use Postgres table partitioning in combination with Citus, for example if you have time-based partitions that you would want to drop after the retention time has expired. A SQL table is decomposed into multiple sets of rows according to a specific sharding strategy. Vertical partitioning was somewhat useful in MyISAM, but rarely useful in InnoDB, since that engine automatically does such. Database sharding vs partitioning I have been reading about scalable architectures recently. We have questions like. Create secondary filegroups and add data files into each filegroup. • Sharding algorithm: an algorithm to distribute your data to one or more shards. 1 Answer. This provides better load balancing compared to user-defined sharding that uses partitioning by range or list. Sharded vs. expr. List Partitioning. : Reviews : Beginner Database Sharding vs Partitioning: Understanding the Key Differences Last Updated on May 25, 2023 CraftyTechie is reader-supported. In this article, we will explore the. Whether you’re sharding by a granular uuid, or by something higher in your model hierarchy like customer id, the approach of hashing your shard key before you leverage it remains the same. In Mongodb each secondary node contains full data of primary node but in Cassandra, each secondary node has responsibility of keeping only some key partitions of data. Dense layer instead of the standard nn. Rather, you can choose to use Postgres native partitioning, or you can shard Postgres with an extension like Citus to distribute Postgres across multiple nodes—or you can use both. Database sharding involves partitioning data across multiple servers, so each server contains a subset of the data. sharding allows for horizontal scaling of data writes by partitioning data across. an index. 4. 131. Add parallelism so FDW requests can be issued in parallel. Just set index. Each partition is a separate data store, but all of them have the same schema. Every shard has an identical schema taken from the original database. Partitioning is the process of breaking a large table into smaller tables. Example: if we are dealing with a large employee table and often run queries with WHERE clauses that restrict the results to a particular country or department . 1. For me this was one of the most confusing aspects of learning this stuff because they are often used interchangeably and there is a certain amount of overlap between the terms. Sharding, a side-by-side comparison How to use range partitioning & Citus sharding together for time series What about sharding using. Each shard is responsible for a subset of the workload, and queries can be. You can limit the amount of data you query by only using a single fully qualified table, or using a filter to the table suffixSharding is a method of partitioning data to distribute the computational and storage workload, which helps in achieving hyperscale computing. April 29, 2022. The word “Shard” means “a small part of a whole“. Partition management is handled entirely by DynamoDB—you never have to manage partitions yourself. Reads are performed within a. I have absolutely no idea how it is possible to somehow optimize such a request. Central to this strategy is database partitioning — serving as the backbone of today’s distributed database systems. Database partitioning is the backbone of modern system design, which helps to improve scalability, manageability, and availability. Partitioning: Splitting a big database into smaller subsets called partitions so that different partitions can be assigned to different nodes (also known as sharding). In this partitioning, each partition is a separate data store , but all partitions have the same schema . Sharding: Partitionning over several server, allowing parallel access (of different datas as opposed to replication) and, as such, memory and cpu load. Note: In addition to the BigQuery web UI, you can use the bq command-line tool to perform operations on BigQuery datasets. ; The value f83a65e0-da2b-42be-b59b-a8e25ea3954c belongs to a single partition, out of the maximum number of partitions defined in the policy (for example: partition number 10 out of a total of 128). Figure 4:Side-by-side comparison of Schema-based sharding vs. The main difference is that partitioning groups these subsets on a single database instance, whereas sharded data can be spread across multiple. Sharding vs. S. Replication -- needed if you have 1000 reads per second. Hashed sharding provides a more even data distribution across the sharded cluster at the cost of reducing Targeted Operations vs. ago. So you would need to go back and rewrite all the database accessing code to pick the right server to talk to for each query. Horizontal partitioning: Splitting the data by group of lines naturally given its primary keys (Row Splitting). I have been reading about scalable architectures recently. Broadcast. Both processes split the database into multiple groups of unique rows. We would like to show you a description here but the site won’t allow us. Horizontal and vertical sharding. Replication, or Replica Sets in MongoDB parlance, is how MongoDB achieves high availability, Replica Sets are a Primary, and 0 to n amount of secondaries which have read-only copies of the. Mỗi partitions có cùng schema và cột, nhưng cũng có các hàng hoàn toàn khác nhau. In this strategy, each partition is a separate data store, but all partitions have the same schema. If you allocate three partitions, your index is divided into thirds. The schema of the table is replicated in every shard, and a unique portion of the whole table lives in. Therefore, the query performance improves significantly, and multiple queries can run in parallel on different machines. “Data is distributed across multiple servers using partitioning, and each partition is further replicated to provide availability. Horizontal partitioning: Each partition uses the same database schema and has the same columns, but contains different rows. Sharding partitions the data-set into discrete parts. Vertical partitioning (schema per table group):. horizontal partitioning or sharding. However, in some use cases it can make sense to partition your database tables where parts of the table are distributed on different servers. Hash Sharding is greatly used for targeted data operations. The three Vs of data storage. In this post, SingleStore Developer Advocate, Joe Karlsson, explains the differences between database sharding vs. . Each shard contains a subset of the data, allowing for better performance and scalability. Rather, you can choose to use Postgres native partitioning, or you can shard Postgres with an extension like Citus to distribute Postgres across multiple nodes—or you can use both. But that assumes no forum is too big to fit on one server. Dynamic sharding is a feature of some database systems that allows the system to manage data partitioning. Horizontal partitioning is achieved in a relational database by storing rows from the same table in several database nodes. Each physical database in such a configuration is called a shard. Then it's like using a database with a much smaller dataset, and that by itself is likely to improve performance a little bit. So, bucketing works well when the field has high cardinality and data is evenly distributed among buckets. Sharding extends this capability to allow the partitioning of a single table across multiple database servers in a shard cluster. Put another way, you Replicate shards; a data-set with no shards is a single 'shard'. In terms of Database Partitioning, its intent is predominantly to enhance query performance in a database. When you shard a database, you create replications of the table schema, then divide what. There is another notable scenario where Redis Cluster will lose writes, that happens during a network partition where a client is isolated with a minority of instances including at least a master. A shard is a horizontal data partition that holds a portion of the complete data set and is thus in the responsibility of serving a portion of the overall demand. Well, if the question is about sharding, then pgpool and postgresql partitioning features are not valid answers. Partitioning: What’s the Difference? Partitioning is a generic term that just means dividing your logical entities into different physical entities for performance, availability, or some other purpose. However sharding is a trade-off. Take as an example our 6 nodes cluster composed of A, B, C, A1, B1. Sometimes federating is right, other times a more generalized partitioning scheme is more suitable. remy_porter • 6 mo. In that context, two words that keep on showing up with regards to databases are sharding and partitioning. Architecture Center Data partitioning guidance Azure Blob Storage In many large-scale solutions, data is divided into partitions that can be managed and accessed separately. Horizontal data partitioning or sharding is a technique for separating data into multiple partitions. As I understand the strategy Cosmos DB use is partitioning with partition keys, but since we use the MongoDB. MongoDB divides the span of shard key values (or hashed shard key values) into non-overlapping ranges of shard key values (or hashed shard key values. Let me elaborate on what’s going on here. The partitioned table itself is a “ virtual ” table having no storage of its. . The basics of partitioning. Unlike Sharding and Replication, Partitioning is vertical scaling because each data partition is in the same. Most data is distributed such that each row appears in exactly one shard. One of the primary differences between sharding and partitioning is how they distribute data. (Seems not applicable to you. Hyperscale computing is a computing architecture that can scale up or down quickly to meet increased demand on the system. Each table contains the same number of rows but fewer columns (see diagram below). For example, if you intend on having a /api/users endpoint, you should have users collection and it should contain any and everything you intend to return on that endpoint. Actual latency for purely in-memory data could be similar. MySQL sharding and partition in distributed system. Sharding is the spreading of horizontal partitions across multiple servers. Each partition forms part of a shard, which may in turn be located on a separate database server or physical location. Hence Sharding means dividing a larger part into smaller parts. So the data in each partition is unique but the schema remains the same. Also if a database is partitioned, it does not imply that the database is definitely sharded. . executor-based partition pruning. Whereas, in network sharding, the entire blockchain network is partitioned into sub-networks called shards. 1Also known as "index-organized table" under Oracle. This would allow parallel shard execution. You still have issue #1 if you use sharding. Partitioning -- won't help the use case you described. Hybrid sharding, as the name goes, is the hybrid of two or more of the aforementioned. Sharding is more general and is usually used when the database is split on several servers. A sharding key is an attribute or column that determines how the data is distributed among the shards. With more than 25 photos and 90 likes every second, we store a lot of data here at Instagram. Build vs Buy for a Sharding Solution Meme Image (Image Source: LinkedIn) To make this choice, you need to consider the cost of 3rd party integration, keeping in mind. Horizontal Partitioning (Sharding): In horizontal partitioning, the database is divided into smaller parts or "shards" based on the rows of a table. Sharding vs Partitioning. In terms of latency, MySQL Cluster should have more stable latency than sharded MySQL. This means that all SELECT, UPDATE, and DELETE should include that column in the WHERE clause. Each partition is a separate data store, but all of them have the same schema. Orthogonally to partitioning or sharding. It helps you in case you need to separate data in a big table to improve performance, or even to purge data in an easy way, among other situations. Through partitioning, databases are thoughtfully segmented into. It is a way of splitting data into smaller pieces so that data can be efficiently accessed and managed. This means that rather than copying data. I want to realize sharding (horizontal partition of table), and I am using SQL Server Standard edition. Imagine a sales database, we can. Even 1 billion rows may not need any of those fancy actions. Each shard is held on a separate database server instance, to spread load. Sharding is possible with both SQL and NoSQL databases. In general less REMOTE / SCATTER -> GATHER pairs means less cluster communication. 1. Partitioning -- won't help the use case you described. There are very few cases where performance is enhanced by such. Hashing your partition key and keeping a mapping of how things route is key to a. Sharding and partitioning are both techniques used to divide and manage large datasets, but they have different approaches and purposes. Each shard is held on a separate database server instance, to spread load. However, Sharding a. This Distributed SQL Tips & Tricks post looks at partitioning vs sharding, scaling limitations in RocksDB. Sharding is a database architecture pattern. Sharding and partitioning are techniques to divide and scale large databases. Later in the example, we will use a collection of books. Table partitioning is the process of splitting a single table into multiple tables. Partitioning is a generic term used for dividing a large database table into multiple smaller parts. A method of splitting and storing a single logical dataset in multiple database instances. partitioning. We achieve horizontal scalability through sharding”. In this strategy each partition is a data store in its own right, but all partitions have the same schema. It is a mechanism to achieve distributed systems. Hashing and modulo. It is useful when no single machine can handle large modern-day workloads, by allowing you to scale horizontally. Sharding, also known as horizontal partitioning, is a popular scale-out approach for relational databases. Partioning implies breaking up the data across multiple tables. The following topics describe the sharding methods supported by Oracle Sharding: System-managed sharding is a sharding method which does not require the user to specify mapping of data to shards. Partitioning -- won't help the use case you described. Essentially, sharding is just a fancy name given to the process of splitting the dataset along its rows. Ta có 3 cách thức Sharding dữ liệu như sau: Horizontal sharding. Sharding and partitioning is great if your query logically touches only one of the shards or partitions. Partitioning stores all data groups in the same computer, but database sharding spreads them across different computers. For example, if a clustered index has four partitions, there are four B-tree structures; one in each partition. sharding. Key Takeaways. Database partitioning is normally done for manageability, performance or availability reasons, as for load balancing. It is popular in distributed database. Partitioning can help with larger tables but only when a small part of the data is hot. Hazelcast named in the Gartner ® Market Guide for Event Stream Processing. Partitioning versus sharding. Auto-sharding — The chunking of data, managing the range depending on the distribution of data across chunks is automatic or called auto-sharding of data. Link back to this blog post. Rather, you can choose to use Postgres native partitioning, or you can shard Postgres with an extension like Citus to distribute Postgres across multiple nodes—or you can use both. 🔹 Horizontal partitioning (often called sharding): it divides a table into multiple smaller tables. Sharding is also referred to as horizontal partitioning. Partitioning is about grouping subsets of data within a single database instance. Note: In addition to the BigQuery web UI, you can use the bq command-line tool to perform operations on BigQuery datasets. In a segment/partition system, it is possible to go back the same memory after swapping but the larger the physical memory, the less likely it will be to return to the same place. See examples of how they can. By default, the operation creates 2 chunks per shard and migrates across the cluster. The word “ Shard ” means “ a small part of a whole “. Sharding in database is the ability to horizontally partition data across one more database shards. Why Hazelcast. This initial. Different sharding strategies fit different scenarios. range partitioning in Apache Spark. sharding is a bit of a false dichotomy. The first engine parameter is the cluster name, then goes the name of the database, the table name and a sharding key. Sharding allows you to scale out database to many servers by splitting the data among them. Sharding is a pattern that divides a data store into horizontal partitions or shards to improve scalability and performance. However, I'm getting confused on when I'd want to create a partition vs. In this diagram, the same colors are used on both sides of the diagram to depict data for each of the 5 tenants (green for tenant1, blue for tenant2, yellow for tenant3, grey for tenant4, orange for. Sharding and partitioning are cornerstone techniques in modern database architectures. The partitioning scheme can significantly affect the performance of your system. This is a topic near and dear to me and I’m excited to think about it some this month. Understanding MongoDB Sharding & Difference From Partitioning. Hash partitioning vs. The key differences are that partitioning occurs on the same server and is supported by MySQL natively, whereas sharding a. This architecture innovation was originally driven by internet giants that run. It also discusses best practices for partitioning and gives an in-depth view at how horizontal scaling works in Azure Cosmos DB. Sharding and partitioning are cornerstone techniques in modern database architectures. For 20+ years of database and application development, time-series data has always been at the heart of the products I work with. Partioning implies breaking up the data across multiple tables. By default, the operation creates 2 chunks per shard and migrates across the cluster. In this post, SingleStore Developer Advocate, Joe Karlsson, explains the differences between database sharding vs. These two things can stack since they're different. In upcoming release Oracle 12. It's not necessary to understand these. MongoDB provides a router program mongos that will correctly route sharded queries without extra application logic. System Design for Beginners: Design for Experienced Engineers: a member. Database sharding involves partitioning data across multiple servers, so each server contains a subset of the data. Distributed. In this video, we dive into the topic of Database Sharding vs Partitioning and break down the key differences between the two. To determine which shard to store any given row, apply the sharding algorithm to the sharding key. Horizontal Partitioning (Sharding) Each partition is a separate data store, but all partitions have the same schema. Each partition is a separate data store, but all of them have the same schema. These shards are not only smaller, but also faster and hence easily manageable. In this tutorial, we’ll discuss two methods for splitting databases into parts to manage them efficiently: sharding and partitioning. Such databases don’t have traditional rows and columns, and so it is interesting to learn how they implement partitioning. Low Shard Key Frequency. Each partition (also called a shard ) contains a subset of data. It allows you to define a combination of sharded tables and unsharded tables. For this month’s PGSQL Phriday #011, Tomasz asked us to think about PostgreSQL partitioning vs. PartitioningBy default, a clustered index has a single partition. Horizontal sharding. Sharding on the other hand, and the load balancing of shards, is a storage level concept that is performed automatically by YugabyteDB based on your replication factor. It results in scanning less data per query, and pruning is determined before query start time. Partitioning on an attribute. Hyperscale computing is a computing architecture that can scale up or down quickly to meet increased demand on the system. Stores possessing IDs of 2001 and greater go in the other. For a faster query response Hive table. Database denormalization. In the first method, the data sits inside one shard. This is where PostgreSQL foreign data wrappers come in and provide a way to access a foreign table just like we are accessing regular tables in the local database. In summary, partitionBy is used to partition the data into separate files based on the values in one or more columns, while bucketBy is used to create fixed-size hash-based buckets based on the values in one or more columns. Step 1: Analyze scenario query and data distribution to find sharding key and sharding algorithm. This is where PostgreSQL foreign data wrappers come in and provide a way to access a foreign table just like we are accessing regular tables in the local database. Range based sharding involves sharding data based on ranges of a given value. Sharding and partitioning are both techniques used to divide and manage large datasets, but they have different approaches and purposes. The technique for distributing (aka partitioning) is consistent hashing”. If you are using mongoDB as a backend for a REST interface, the best practice is to create on collection per resource. Figure 1 is an example of a sharding database. Partitioning or Sharding at row level provide all SQL and ACID. g. 1y. The split can happen vertically (so the table has fewer columns), horizontally (so the table has fewer rows). Each partition has the same schema and columns, but also entirely different rows. Both approaches have their own strengths and weaknesses, and the best approach for a given situation will depend on the specific. By default, the operation creates 2 chunks per shard and migrates across the cluster. By distributing data among multiple instances, a group of database instances can store a larger dataset and handle additional requests. Sharding is a database scaling technique based on horizontal partitioning of data across multiple independent physical databases. Each shard contains a subset of the total rows and functions as a smaller independent database. Sharding, at its core, is a horizontal partitioning technique. SQL Server requires application-level logic for sending queries to the best node . It is the simplest sharding algorithm and can be used to evenly distribute data among shards and prevent the risk of having a database hotspot. Sharding is necessary as the number of records in the relationship table can easily exceed the storage space of any drive. I feel. As I understand, in postgres, db level sharding is mostly done by partitioning the tables and moving each partition into seperate instance like shown bellow. While the declarative partitioning feature allows users to partition tables into multiple partitioned tables living on the same database server, sharding allows tables. When partitioning a table, you need to consider having enough data for each partition. It can also be functional (which maps rows of data into one partition or the other depending on their value). Amazon Relational Database Service (Amazon RDS) is a managed relational database service that provides great features to make sharding easy to use in the cloud. In our exploratory scheme, each partition is a foreign table and physically lives in a separate database. Or you want a separate backup machine. Database sharding vs partitioning. In the context of scaling MongoDB: replication creates additional copies of the data and allows for automatic failover to another node. Horizontal partitioning is often referred as Database Sharding. Sharding is a technique to split the table up between different machines. Should I do a Sharding? Sharding should be done only when it’s absolutely. Our application is built on J2EE and EJB 2. Horizontal partitioning or sharding. You can use numInitialChunks option to specify a different number of initial chunks. In a key- or hashed -based sharding architecture, a database application uses a shard key to locate a shard. Sharding means partitioning a neural network, represented as a computational graph, across multiple IPUs, each of which computes a certain part of this graph. Database sharding and partitioning. number_of_shards. Database sharding is a technique for horizontal scaling of databases, where the data is split across multiple database instances, or shards, to improve performance and reduce the impact of large amounts of data on a single database. 131. The table is partitioned into “ranges” defined by a key column or set of columns, with no overlap between the ranges of values assigned to different partitions. Algorithmically sharded databases use a sharding function (partition_key) -> database_id to locate data. It separates very large databases into smaller, faster and more easily managed parts called data shards. Both are methods of breaking a large dataset into smaller subsets – but there are differences. For a more detailed explanation of sharding and the auto-sharding mechanics in YugabyteDB, check out Distributed SQL Sharding: How Many Tablets, and at What Size? P. It’s important to note. Whether organizing data within a database or distributing it across servers, understanding their nuances and. Sharding vs. Another advantage of sharding is being able to use the computational. Now the requests will be routed across shards in the partition rather than one (basic routing) or all shards (no routing) in the index. e. The database hotspot problem arises when one shard is accessed more as compared to all other shards and hence, in this case, any benefits of sharding the. Each partition is created based on the partitioning key. Which shard contains a each document in a collection depends on the overall "Sharding" strategy for that collection. Database partitioning is normally done for manageability, performance or availability reasons, as for load balancing. In case of replicating existing shards, there will be more hosts to respond to a query request. Data is organized and presented in "rows," similar to a relational database. In this case, the records for stores with store IDs under 2000 are placed in one shard. The replication strategy determines where replicas are stored in the cluster. • Sharding algorithm: an algorithm to distribute your data to one or more shards. When a clustered index has multiple partitions, each partition has a B-tree structure that contains the data for that specific partition. Horizontal Partitioning (sharding) stores rows of a table in multiple database clusters. Sharding Typically, when we think of partitioning, we’re describing the process of breaking a table into smaller, more manageable tables on the same database server. In many cases , the terms sharding and partitioning are even used synonymously, especially when preceded by the terms “horizontal” and. The Partition Key is hashed and then divided by the number of shards. Shard: A chunk of an index. A distributed SQL database needs to automatically partition the data in a table and distribute it across nodes. In version 11 (currently in beta), you can combine this with foreign data wrappers, providing a mechanism to natively shard your tables across. Sharding is used when Partitioning is not possible any more, e. Both are used to improve query performance, but they achieve this in different ways. But there’s two new things: There’s a new shard_axes argument being passed into the layer definition on lines 11 and 21. It seemed right to share a perspective on the question of “partitioning vs. Comparison of database sharding and partitioning. Sharding: Handles horizontal scaling across servers using a shard key. BTW, Oracle cluster is different thing from Oracle index-organized table. This article explores when to use each – or even to combine them for data-intensive applications. Define logical boundary for each partition using partition function. Hashed sharding uses either a single field hashed index or a compound hashed index (New in 4. However, it does have a drawback with aggregating data across the multiple databases. –Vertical Partitioning In contrast to horizontal partitioning, vertical partitioning lets you restrict which columns you send to other destinations, so you can replicate a limited subset of a table's columns to other machines. Database sharding is a technique used to optimize database performance at scale. 16. The CAP always applies, it says user failure to acces data means either interruptions or inconsistencies. Replication may help with horizontal scaling of reads if you are OK to read data that potentially isn't the latest. By default, Spark/PySpark creates partitions that are equal to the number of CPU cores in the machine. BigQuery: date sharding vs.