Elasticsearch Aggregation Group By Multiple Fields

Search everywhere only in this topic Advanced Search. Aggregation - Blank and date aggregation; ElasticSearch Aggregation Result In Asending Order of any Field Value (Instead of aggregation field count order) Restricting Bucket Aggregation to Certain Values; doc values; Terms Aggregation buckets returns only single words and not phrases. I have some numeric fields in elasticsearch, I have to implement some logic for which I need to create some scripted fields. I have a requirement to fetch the data from ES. To help, this guide will take you through the ins and outs of search queries and set you up for future searching success. A customer could land on a product page by coming from a recommendation on another page in your application or from a search engine. In case you are familiar with relational databases, you can think of this as the equivalent of SQL’s GROUP BY clause and aggregate functions such as SUM. Sort by multiple columns or expressions Aggregate functions vs NULL value; GROUP BY clause and Numpy Data Science Programme Elasticsearch for Developers Excel. MS SQL Server, a Relational Database Management System (RDBMS), is used for storing and retrieving data. Elasticsearch doesnt support something like 'group by' in sql. Can't group/aggregate by keyword fields #12029. 当执行一个搜索时,它将这个搜索请求广播给所有的索引分片。可以通过提供路由参数来控制要搜索哪些分片。例如,当检索tweets这个索引时,路由参数可以设置为用户名: 1. Hear what our customers have to say about Seq. This is a pain because if you want to properly visualize a set of log messages gathered from multiple systems, in sequence, to be able to see exactly what step followed the other…. This study assesses the impact of structural changes and outliers on volatility persistence of three crude oil markets - Brent, West Texas Intermediate (WTI) and Organization of Petroleum Exporting Countries (OPEC) - between January 2, 1985 and June 17, 2010. For example, if I group by the sex column and call the mean() method, the mean is calculated for the three other numeric columns in df_tips which are total_bill, tip, and size. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. This query accepts multiple queries and then returns the documents matching any of the query clauses. elasticsearch aggregation - The aggregations framework helps provide aggregated data based on a search query. To execute any GROUP BY statement it should first order the records according to GROUP BY conditions. Elasticsearch provides an Indices Filter, a Type Filter, and an Indices Query which can be used when working with multiple indices and types. How to aggregate multiple child columns with parent column only once when not grouping by parent? I have two tables where a parent can have multiple children. ; to aggregate. The power of an Elasticsearch cluster lies in the distribution of tasks, searching and indexing, across all the nodes in the cluster. Similarly to facets (now deprecated), aggregations allow calculating and summarizing data of a query as it happens. Aggregation operations, such as distinct, count, and average on large data sets, are traditionally run on batch processing systems, such as Hadoop, due to the heavy computation involved. The StatisticalFacet is great, but often-times the statistical data is required per some kind of "group", and not only on some kind of filter over the whole data. These can be shown as e. For example, while selecting a list of rows you can also calculate count of rows sharing the same field values without using subselects or SQL CTE (Common Table Expressions) in your query. A system with identical design principles could be implemented by single or multiple donors for individual or multiple forest proprietors within one or more countries, as well as national or local governments in individual countries, tropical regions, or the global pan-tropics. Mapping is the outline of the documents stored in an index. 89447236077427. For instance the following example computes the average value of a field per composite bucket:. But this approach was a failure because it could harm the main memory while. Elasticsearch also spreads replicas across the. lucene query and then you choose which field and aggregation you want (sum, average etc. So let us jump on example and implement it for multiple columns. Use familiar frameworks like PyTorch, TensorFlow, and scikit-learn, or the open and interoperable ONNX format. The SQL GROUP BY clause can be used in a SELECT statement to collect data across multiple records and group the results by one or more columns. a total field whose value is the sum of all the Units field values from each of the documents in the group; We can check the stage input, which we expect to be 89 documents. frame on 1 or multiple dimensions using 1 or multiple functions for different columns. 0 of ElasticSearch, the new aggregations API allows grouping by multiple fields, using sub-aggregations. Loved at leading companies. GROUP BY 语句. I'm trying to combine values from multiple observations into one field. Optimizing Sum, Count, Min, Max and Average with LINQ. You received this message because you are subscribed to the Google Groups "elasticsearch" group. For more information about Delta Lake, see Delta Lake. Detailed comparison post between Apache Solr vs Amazon CloudSearch vs ElasticSearch. Currently, we are continuing to improve our self-published Internet-Drafts. 59879638879274 1497979290000000000 host2 98. SQL Count with Partition By clause is one of the new powerful syntax that t-sql developers can easily use. Ask Question Asked 3 years, 7 months ago. Suppose you have a number of columns in a wide table that you would like to unpivot into a single column and multiple rows. It caters to both search and analytics. Introduction to Elasticsearch Praveen Manvi July 2016 2. Bucket aggregations. You can prevent the generation of the auto group columns and take control over which columns display which groups. With the exception of the aggregations functionality this means that the Search object is immutable - all changes to the object will result in a shallow copy being created which contains the changes. This is Python's closest equivalent to dplyr's group_by + summarise logic. As an example, let's assume a Lucene index contains two fields, title and text and text is the default field. These subqueries can have their scoring tuned as well, to better balance the scores of the various subqueries. right-click on the field you want to analyze and choose Select Multiple. The StatisticalFacet is great, but often-times the statistical data is required per some kind of "group", and not only on some kind of filter over the whole data. How to aggregate over matched fields in an array in elastic search. To understand the MongoDB group by multiple fields first, let’s have a look at a list of all operators that can be used in $ group:. The agg() method allows us to specify multiple functions to apply to each column. Applying a function to each group independently. Optimizing Sum, Count, Min, Max and Average with LINQ. \*":"(North South) Aggregation. Here is how such a definition looks like (inside Kibana):. Elasticsearch Aggregation time. to sort or aggregate by. Closed k2xl opened this issue k2xl changed the title Can't group by keyword fields? Can't group/aggregate by This should be much more reliable than our field_stats implementation as Elasticsearch can express field capabilities based on mappings alone rather than figuring it out from. Generally, these functions are aggregate functions such as min(),max(),avg(), count(), and sum() to combine into single or multiple columns. You can vote up the examples you like and your votes will be used in our system to generate more good examples. The aggregate function is one of the most capable functions in the scidb package. Elasticsearch Aggregrations. i am Looking for the best way to group data in elasticsearch. Add a Having clause to filter the aggregate values that are generated by the Group By clause. --You received this message because you are subscribed to the Google Groups "elasticsearch" group. Useful if the grouping variable is some experimental variable and data are to be aggregated for plotting. Multiple this by the number of aggregations you compute in one go and… MySQL 31ms vs. For example, terms aggregation query shown above is very similar SQL group by. We’ve read that Elasticsearch […]. If you don't group by any columns, you'll get a 1-row result—no problem there. How to get group by sum in Elastic search (Nest Client C#) #1142. py, change this index in this line of code: Basically ElasticSearch is saying that doing aggregation on the text fields would require calculating extra data and holding that in memory. Aggregate functions are frequently used with the GROUP BY clause of the SELECT statement. how to use multiple aggregate attributes and a Multiple group by. When doing an aggregation query to find out how many Members and Discussions there're for a specific Group(s) the aggregation which is 2nd ends up having a duplicated doc_count. Sort by multiple columns or expressions Aggregate functions vs NULL value; GROUP BY clause and Numpy Data Science Programme Elasticsearch for Developers Excel. Aggregate Functions with Group BY and HAVING clause: We use aggregate functions SUM, COUNT, AVG, MAX, MIN etc. This tutorial is for the beginers who want to learn Elasticsearch from the scratch. Multiple this by the number of aggregations you compute in one go and… MySQL 31ms vs. It improves aggregate network throughput and benefits both Wave 2 & non-Wave 2 clients. Example below shows us how to use some of them in elasticsearch. aggregations give the insight of our data and can be used for a wide range of problems like we can use Elasticsearch aggregations for creating a recommendation engine through which we can implement the recommendation system on any website. There are also limitations with the basic. The input parameters must include points to be aggregated and aggregation areas. Elasticsearch is able to achieve fast search responses because, instead of searching the text directly, it searches an index instead. There are also limitations with the basic. Master the latest distributed search and analytics capabilities of Elasticsearch 7. Here is a cut-down example I have a mapping that has parent documents of type 'datastreams'. Without learning how to do aggregation in Google Sheets Query, you can’t well manipulate your data. New here? Start with our free trials. It was developed by Shay Banon and published in 2010. How to dynamically group list by multiple columns and create pivot table with NReco PivotData. name” must appear in the GROUP BY clause or be used in an aggregate function” But, this query is perfectly fine: SELECT string_agg(name, ', '), count(1) FROM products GROUP BY category; Multiple columns can be included in the GROUP BY clause, separated by commas. For further information on Spark SQL, see the Spark SQL, DataFrames, and Datasets Guide. The built-in within-group ordered-set aggregate functions are listed in Table 9. As an example, let's assume a Lucene index contains two fields, title and text and text is the default field. The following aggregation operation specifies a group _id of null, calculating the total sale amount, average quantity,. over 3 years Terms query not in filter context; over 3 years Grand children aggregation is returning the zero result in elasticsearch 2. jimczi opened this issue Nov 28, This is due to the fact that each group can appear in multiple shards. We’ll imagine that we want to find not just the number of recipes per author, but also the number of recipes an author has per the different categories. Finally, you have to specify the aggregation type terms and the specific option. See Also Elastic. Buckets can be created based on an existing field, custom filters, ranges, and so on Metric aggregation: This can be used to calculate a metric, such as a count, sum, average, and so on; Pipeline aggregation: This can be used to chain aggregations. In addition to basic bucketing and metrics aggregations like these, Elasticsearch provides specialized aggregations for operating on multiple fields and analyzing particular types of data such as dates, IP addresses, and geo data. Elasticsearch doesnt support something like 'group by' in sql. This is a pain because if you want to properly visualize a set of log messages gathered from multiple systems, in sequence, to be able to see exactly what step followed the other…. Aggregations are a way of grouping and extracting statistics from your data. We could easily create a tag cloud by using an aggregation. Then documents with the same values are further sorted by. Having had its start as a search engine, Elasticsearch defaults to a full-text search use-case. Elasticsearch Aggregrations. Michael Cooper Recommended for you. i am Looking for the best way to group data in elasticsearch. SQL SUM() using multiple columns with group by. Term stat facets on multiple fields. It is now maintained by Elasticsearch BV. In this post we are going to see the limitations of the date_histogram aggregation in certain cases, and how to overcome that by employing elasticsearch scripting. Such schools use experiential learning and a group approach to facilitate farmers in making decisions, solving problems, and learning new techniques. e TotalCallCompleted from Fetch XML 1 query, but unable to get Total callback request from Fetch XML 2 query. The aggregation functionality provided by the agg() function allows multiple statistics to be calculated per group in one calculation. In this article, we move on to various scripting options that are available for managing ES aggregations. Bucket aggregations. Elasticsearch is built on Java and requires at least Java 8 (1. ; to aggregate. Get to grips with the basics of Elasticsearch concepts and its APIs, and use them to create efficient applications; Create large-scale Elasticsearch clusters and perform analytics using aggregation. Elasticsearch has enabled us to provide user experiences that were once difficult or too slow for our users utilizing traditional relational databases. Starting from version 1. So the first one is used to identify. Hence, I have referred to the Country (38,06), as a criterion to group data. Multiple high level aggregations via the "group by" #73. I have objects with an array named properties. 集約について考える上で最も簡単な方法は、集約とSQL GROUP BY機能およびSQL集約機能を同等とみなすことです。Elasticsearchでは、ヒットを返す検索を実行すると同時に、ヒットとは別の集約された結果を1つの応答にまとめて返すことができます。. For example, given an index of investment data field1 might be investor and field 2 might be the. Pivoting and Unpivoting Multiple Columns in MS SQL Server aggregate_function: FROM cte_result WHERE MovieId <= 2 GROUP BY ROLLUP(movieid,title,star) )ratingfilter. So let’s get started. You can group by any numeric field but for text fields that have to be of type keyword or have fielddata=true. Nguyen Manh Tien Check terms aggregation, it allow return specified top field in a group, can i return the whole doc there? -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. Power Query has two types of Group By operations: aggregate a column with an aggregate function, or perform a row operation. Here is one example to demonstrate different methods to handle that. 4, buckets of documents coming from other aggregations. Ah, now I understand. databasestar. Elasticsearch - Ignore special characters in query with pattern replace filter and custom analyzer; Elasticsearch 5 Determining if nested field exists; Elasticsearch deprecation warning: [deprecation. 0 has been released. A nested aggregation allows you to aggregate a field with nested documents—a field that has multiple sub-fields. Aggregate Functions with Group BY and HAVING clause: We use aggregate functions SUM, COUNT, AVG, MAX, MIN etc. If you are familiar with SQL, then you'll be familiar with the group by clause. Elasticsearch is an open source search and analytic engine based on Apache Lucene that allows users to store, search, analyze data in near real time. For more information, see Section 12. We did an in-depth analysis of these databases with respect to parameters such as data storage models, data ingestion methods, database architectures, deployment models, specialized querying capabilities, licensing models, and availability of enterprise support. It is really providing awesome searching capabilities, good json structure documents etc Currently I am stuck up with the problem on How to write group by query and. To do aggregate in SQL we use GROUP BY clause. See Also Amazon Elasticsearch Service (Amazon ES). Let's discuss how to do aggregations with nested documents in Elasticsearch. A family of aggregations that operate on multiple fields and produce a matrix result based on the values extracted from the requested document fields. Search everywhere only in this topic Advanced Search. If the DISTINCT aggregate is on the leading GROUP BY key(s). , Software Engineer Mar 23, 2016 It’s 10:51 PM on a Friday, and someone on the internet has decided to try. In all the previous examples the grid is in charge of generating the column's that display the groups, these columns are called auto group columns. Write queries that return: How many individuals were counted in each year: (a) in total; (b) per each species. The following are top voted examples for showing how to use org. See example of Group by Null. Yes, you can group data by multiple fields. Learn how to calculate multiple aggregate functions in a single query with filtered aggregate functions, the FILTER clause, the PIVOT solution, and more. There are many types of aggregations but in this particular case where we want to group by the exact value in a field a terms aggregation is suitable. The ROLLUP option allows you to include extra rows that represent the subtotals, which are commonly referred to as super-aggregate rows, along with the grand total row. SQL to ReQL cheat sheet. name” must appear in the GROUP BY clause or be used in an aggregate function” But, this query is perfectly fine: SELECT string_agg(name, ', '), count(1) FROM products GROUP BY category; Multiple columns can be included in the GROUP BY clause, separated by commas. Elasticsearch provides an Indices Filter, a Type Filter, and an Indices Query which can be used when working with multiple indices and types. From Elasticsearch 1. Now, let us jump to the Elasticsearch aggregations and learn how we can. The parent-child functionality allows us to associate one document type with another, in a one-to-many relationship, or one parent to many children. But then it seems to add up all the value fields when calculating. databasestar. * The contents of all metadata fields that are held in the catalog, and that contain data about the catalog itself and its dataset and distributions, are included in this RDF description, expressed using the appropriate classes and properties from DCAT, except where no such class or property exists. You can use aggregate functions with any of the columns that you select. value I was then able to create visualizations where this scripted field was used as the terms bucket for the x-axis. Groupby Function in R – group_by is used to group the dataframe in R. Elasticsearch tries to have sensible defaults so this is something that generally doesn't need to be configured. In this article, we’ve had a look at available T-SQL options for transposing rows into columns. Suppose you want to group by fields field1, field2 and field3:. Such schools use experiential learning and a group approach to facilitate farmers in making decisions, solving problems, and learning new techniques. The result of the query is emitted as a new event, while the original events are omitted. 11ac Wave 2 to the mid-tier segment. say we want to group them up by a 'type' field In SQL dialects this might look something like 'SELECT * FROM foo GROUP. Example - Field's name is Country it has 6 unique values elasticsearch aggregation group by null key. we want to group with in Group by and. SQL SELECT with DISTINCT on multiple columns: Multiple fields may also be added with DISTINCT clause. docId WHERE dt. For example, if you want to view a list of student names and email addresses, but you do not want to see addresses and other data, you can create a query that displays the student’s first name, last name, and email address only. 0 of ElasticSearch, the new aggregations API allows grouping by multiple fields, using sub-aggregations. Aggregations in Power BI let you reduce table sizes so you can focus on important data and improve query performance. In the past few articles, we have focused on indexing and searching parent-child relationships in elasticsearch. The aggregation functionality provided by the agg() function allows multiple statistics to be calculated per group in one calculation. Get built-in support for open-source tools and frameworks for machine learning model training and inferencing. First group by at the lowest level, next group by the higher level, adding aggregation "all rows": This is the generated code, in which Value. Mongodb Group by Multiple Fields. Select the aggregate function that you want to use for this field, and click the OK button. Detailed comparison post between Apache Solr vs Amazon CloudSearch vs ElasticSearch. 3, “MySQL Handling of GROUP BY”. Multiple Grouping Columns. The SQL GROUP BY Statement. It caters to both search and analytics. Some metrics and group by clauses haves options, click the option text to expand the row to view and edit metric or group by options. The security group was configured to enable access from anywhere using SSH and TCP 5601 (Kibana). We use ElasticSearch extensively at our company but we don't use it for full text search (in fact, we don't use its full text capabilities at all) but rather for its ability to match and aggregate large data sets without having to create any indexes at all prior (and it's fast, it still blows my mind a little). Terms aggregation for multiple fields. Elasticsearch is able to achieve fast search responses because, instead of searching the text directly, it searches an index instead. the poller with wildcard configurations that match multiple services. Related Searches to Multi-fields in elasticsearch elasticsearch multi_field example elasticsearch multi_field deprecated elasticsearch mapping fields raw elasticsearch multi field analyzer multi_field elasticsearch 5 no handler for type [multi_field] declared on field multi field meaning elasticsearch add raw field. Within a search engine, mapping defines how a document is indexed and how its fields are indexed and stored. to perform mathematical calculation on data retrieved by SOQL query. Aggregations in Power BI let you reduce table sizes so you can focus on important data and improve query performance. The ROLLUP option allows you to include extra rows that represent the subtotals, which are commonly referred to as super-aggregate rows, along with the grand total row. But then it seems to add up all the value fields when calculating. Elasticsearch tries to have sensible defaults so this is something that generally doesn’t need to be configured. December 2013 elasticsearch Elasticsearch Aggregations Overview. In all the previous examples the grid is in charge of generating the column's that display the groups, these columns are called auto group columns. Search Lite. UNPIVOT performs the opposite operation to PIVOT by rotating columns of a table-valued expression into column values. The following code should just get the sum of the price of cars, based on the the type of the car. Creating Group-Level Aggregate Elements You can use the data model editor to aggregate data at the group or report level. For example, when you create a total for a year, you are creating an aggregation. This document. GROUP_CONCAT function concatenates values within each group defined by GROUP BY clause. A field is the smallest unit of data in Elasticsearch. In this case age is not text so we do not have to use keyword version of field. If you are familiar with SQL, then you'll be familiar with the group by clause. As I see you need to nest the sum aggregation in the scope of the port aggregation, then you will get the sum (visits) inside the bucket of ip and port together. Thanks Vineeth -- You received this message because you are subscribed to the Google Groups "elasticsearch" group. To demonstrate this, we’ll add a fake data column to the dataframe # Add a second categorical column to form groups on. SPARK SQL replacement for mysql GROUP_CONCAT aggregate function? 1 Answer. springframework. That's not. Do you know that you can link slicer to more than one pivot table? Yes, this advanced usage of slicers makes it handy to update multiple reports with one click. See example of Group by Null. Another option is to use Script Filter support from ES described below. While Elasticsearch is designed for fast queries, the performance depends largely on the scenarios that apply to your application, the volume of data you are indexing, and the rate at which applications and users query your data. If you don't group by any columns, you'll get a 1-row result—no problem there. To get such a list of popular tags in Elasticsearch, you'd use aggregations, and in this specific case, you'd use the terms aggregation on the tags field, which counts occurrences of each term in that field and returns the most frequent terms. Aggregations in Power BI let you reduce table sizes so you can focus on important data and improve query performance. Let's discuss how to do aggregations with nested documents in Elasticsearch. 74/5 rating based on 20 reviews This 2-hour online course focuses on E-commerce or similar product search use-cases …. You can think of keyword as being like an index. Choose the three fields of OrderDateKey, CustomerKey, and ProductSubcategoryKey in the Group By fields. The $ group operator is an aggregator that returns a new document. 当执行一个搜索时,它将这个搜索请求广播给所有的索引分片。可以通过提供路由参数来控制要搜索哪些分片。例如,当检索tweets这个索引时,路由参数可以设置为用户名: 1. All the columns in SELECT clause on which any aggregation is not done must be part of GROUP BY clause in SQL. 57 while the built-in within-group hypothetical-set ones are in Table 9. Hear what our customers have to say about Seq. As you can see, the result of the aggregation will have the group names as the new index along the grouped axis. So far we have seen the grouping of documents based on various aggregations like term, date histogram, and more. For example, terms aggregation query shown above is very similar SQL group by. Below is the above request updated to include a terms aggregation for the director field. You received this message because you are subscribed to the Google Groups "elasticsearch" group. codingexplained. This is a pain because if you want to properly visualize a set of log messages gathered from multiple systems, in sequence, to be able to see exactly what step followed the other…. Eg : I have a field called Brand,Name,Category. At least 1 value must be specified. 4 September 2014. They allow as to compose bucket of documents which falls into given criterion or not. These aggregation queries are what powers pretty much all data visualizations you see in tools like Kibana, Grafana, and others. To get such a list of popular tags in Elasticsearch, you'd use aggregations, and in this specific case, you'd use the terms aggregation on the tags field, which counts occurrences of each term in that field and returns the most frequent terms. The GROUP BY statement is often used with aggregate functions (COUNT, MAX, MIN, SUM, AVG) to group the result-set by one or more columns. Remember that, because the field is non-analyzed, the. 0 has been released. Hear what our customers have to say about Seq. Metrics aggregations. The development of NoSQL databases was triggered by the needs of the companies dealing with huge amounts of data like Facebook, Google and Amazon. This kind of aggregate expression is evaluated for each line group defined in GROUP BY and its result is used as an operand in the comparison. The following code should just get the sum of the price of cars, based on the the type of the car. In distributed computing, it is desirable to divide such computations into smaller pieces, and distribute the work, usually computing in parallel, via a divide and conquer algorithm. Elasticsearch is an open source, distributed and JSON based search engine built on top of Lucene. Applying a function to each group independently. The query language used is acutally the Lucene query language, since Lucene is used inside of Elasticsearch to index data. s…" 3 days ago Up 3 days 0. 5, you can fetch the parents as well by adding the inner_hits object to the query. Group Aggregation. I also want to favor hits with certain fields. Change the aggregation used by a field on an Amazon QuickSight visual. GroupBy allows you to group rows together based off some column value, for example, you could group together sales data by the day the sale occured, or group repeast customer data based off the name of the customer. com/course/elasticsearch?src=youtube. weight) AS tot FROM DocumentTags dt LEFT JOIN Lines l ON dt. Currently, we are continuing to improve our self-published Internet-Drafts. Reading Time: 2 minutes First of all we need to understand aggregation in ElasticSearch. The GROUP BY statement groups rows that have the same values into summary rows, like "find the number of customers in each country". Single line for multiple matrics. Multiple Grouping Columns. This document. Suppose you have a dataset containing credit card transactions, including: the date of the transaction; the credit card number; the type of the expense. Another area where ElasticSearch shines is its aggregations features. TermsBuilder. It supports filtering, searching, sorting, grouping and aggregating in ElasticSearch for date, number (double only) and string fields. Eg : I have a field called Brand,Name,Category. Aggregation operations group values from multiple documents together, and can perform a variety of operations on the grouped data to return a single result. It is formatted in JSON and has a record with three fields id, name, and sale that correspond to the table columns. GROUP BY Syntax. 9, it comes with better aggregation features, some security and scripting improvements, several index performance improvements and more. Such schools use experiential learning and a group approach to facilitate farmers in making decisions, solving problems, and learning new techniques. sysparm_having: An additional query allowing you to filter the data based on an aggregate operation. We use ElasticSearch extensively at our company but we don't use it for full text search (in fact, we don't use its full text capabilities at all) but rather for its ability to match and aggregate large data sets without having to create any indexes at all prior (and it's fast, it still blows my mind a little). Aggregation columns in the aggregated table should follow. How can I select all columns as 1 column? Mongoosejs: Cleanest way to select rows with `limi Elasticsearch Nested Indexing using Pentaho Data I How to join Multiple table using hibernate criteri Oracle MERGE - if not matched then update if condi SQL - Split One Table to Two And Link; run php script on same site. Any examples would be very useful. Group Aggregation. PageImpl