Paging behaviors and ordering
When querying data using FetchXML, paging query results can make viewing large volumes of information easier. It is important when using paging to include ordering parameters as well. Without proper ordering, paging requests for the “next 50” records can result in retrieving the same records across multiple pages making reviews and edits much more difficult. Proper page ordering requires including unique values to help identify which records are included in a page.
Legacy paging within the Microsoft Dataverse loads all the results of the query up to the current page into memory on the server, selects the number of records that are needed for the page, and then ignores the rest. This has benefits such as quick back/forward paging through the data or skipping to a specific page, but it also has restrictions such as a 50K row limit, performance issues with large complex queries, and arbitrarily sorted distinct query results.
Ordering with a paging cookie
When paging with ordering, a cache of the previous page’s results is stored in a paging cookie. This is used to calculate what the next page of data should display.
If a user does not specify any “order by” parameters, the system will automatically insert “order by "<<entity name>>".<<entityId>> asc” to provide some basic ordering. Depending on the data that is being queried, this may result in inadequate and unexpected results as a single system user can be associated with multiple records within any query.
If distinct FetchXML queries are being used, the system will not add any additional ordering due to potential impacts to the data returned. In these cases, users will have to add at least a single ordering value for a more consistent paging experience.
Paging using FetchXML for Dataverse is dynamic. The page a record appears on is determined at the time that each page is rendered. If 1000 records are being displayed 50 to a page, the first 50 records are displayed as page one. When page two is requested, the system determines what the next 50 records should be at the time of request. Because of this, it would not be possible to use the new paging functionality for back paging. Legacy behavior is used for back paging which will have reduced performance and any returns after page 500 cannot be “paged back” due to legacy limitations. ￼
Why ordering is important
If a query is run to retrieve all records with a state of “Open” this could result in 1000 returns. When paging from page one to page two, there is no way for the system to know which orders to display on page two because all of the records have the same state. The paging of these records will not be efficient or consistent.
Providing an “order by” value gives the paging cookie the ability to order the data by an additional value and recognize the last record in a page based on the values provided.
A query is created to get all records with a state of ‘Open’, include the status for every record, and show three records per page. The query is then ordered by status. The query result would page as shown in the following table:
|Open||Active||End of page 1|
The paging cookie will save information about the last record on the page, but when it’s time to get page two in this example, there is no unique identifier to ensure that the next page populated uses the unviewed records or include the first two records that were on page one.
To solve this problem, queries should include “order by” columns that have unique values. It is possible to use multiple “order by” values. Below is a better way to order data for this query:
A query is created to get all records of a state of ‘Open’, any status, include the Case IDs, and show three records per page. It orders by status and by Case ID (a unique identifier) which will order in ascending order. The query result would page the results as shown below:
|Open||Active||Case-0032||End of Page 1|
The query results are first ordered by the Status, and then ordered by the Case ID in ascending order. When page two is generated, the result would be as shown below:
|Open||Active||Case-0032||End of Page 1|
When generating page two of this query set, the cookie will have Case-0032 stored as the last record in the first page, so page two will pick up at the next record in the set after that record. This will allow for more consistent results.
Listed below are some suggestions for improving ordering of paging results, along with some areas to avoid.
- Always include a column that has a unique identifier (i.e., table ID columns, auto-number columns, user/contact IDs)
- Include multiple fields that will most likely result in unique combinations:
- First name + last name + email address
- Full name + email address
- Email address + company name
Orders that do not include unique identifiers
Orders that have single or multiple fields that are not likely to provide uniqueness such as:
- Status and state
- Choices or Yes/No
- Name values by themselves (i.e., last only, first only, company name only)
- Text fields like titles, descriptions, multi-line text
- Non unique number fields
Ordering and multiple table queries
Sometimes data is needed that spans multiple tables and must be queried with a table JOIN. In these cases, ordering can be included for both tables in the query. Make sure to use at least one column with a unique ID per table to ensure the paging provides the best results. However, the query will be downgraded to legacy paging, where no paging cookie will be returned, in these cases due to limitations of the N:1 relationship structure that could result in missing data.