I don't see any difference in the runtimes, at least not with the current head of trunk ...
sqlite> .once x sqlite> select * from invoices; Run Time: real 0.032 user 0.031250 sys 0.000000 sqlite> .once y sqlite> SELECT ShipName, ShipAddress, ShipCity, ShipRegion, ShipPostalCode, ShipCountry, Orders.CustomerID as CustomerID, Customers.CompanyName, Customers.Address, Customers.City, Customers.Region, Customers.PostalCode, Customers.Country, ...> Employees.[FirstName] || ' ' || Employees.[LastName] AS Salesperson, ...> Orders.OrderID as OrderID, OrderDate, RequiredDate, ShippedDate, ...> Shippers.CompanyName, Products.ProductID as ProductID, ProductName, [Order Details].UnitPrice as UnitPrice, Quantity, Round(Discount,4) as DisCount, Round([Order Details].UnitPrice * Quantity * (1-Discount), 2) AS ExtendedPrice, Freight FROM ...> Orders INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID ...> INNER JOIN Employees ON Employees.EmployeeID = Orders.EmployeeID ...> INNER JOIN [Order Details] ON Orders.OrderID = [Order Details].OrderID ...> INNER JOIN Products ON Products.ProductID = [Order Details].ProductID ...> INNER JOIN Shippers ON Shippers.ShipperID = Orders.ShipVia ...> Order By OrderID; Run Time: real 0.031 user 0.031250 sys 0.000000 sqlite> sqlite> .once x sqlite> SELECT * FROM Products JOIN [Order Details] Using(ProductID) ...> Order By OrderID ...> ; Run Time: real 0.015 user 0.015625 sys 0.000000 sqlite> .once y sqlite> Select * From [Order Details Extended] ; Run Time: real 0.016 user 0.015625 sys 0.000000 sqlite> --- The fact that there's a Highway to Hell but only a Stairway to Heaven says a lot about anticipated traffic volume. >-----Original Message----- >From: sqlite-users [mailto:sqlite-users- >boun...@mailinglists.sqlite.org] On Behalf Of Olaf Schmidt >Sent: Friday, 27 October, 2017 12:21 >To: sqlite-users@mailinglists.sqlite.org >Subject: [sqlite] Small Performance Regression (3.21.0) > >The new CoRoutine-approach seems to slow down certain >ViewDefinitions (in comparison to running a Query directly). > >FWIW, here's a download-link to an NorthWind-SQLite-DB, which >already contains certain view-definitions: >http://vbRichClient.com/Downloads/NWind.zip >(an "Analyze"-command was already run against that DB). > >The one view-def (where the difference is most apparent) is >[Invoices]: > >Here a: Select * From Invoices >needs about 20msec. > >Whereas running the SQL of the View-definition directly, >needs only about 10msec. > >A simpler view-definition in the above zipped NWind.db is: >[Order Details Extended] > >Which is defined with the following SQL: >SELECT * FROM Products JOIN [Order Details] Using(ProductID) >Order By OrderID > >When run directly, it comes up with the result after ~4msec, >whereas: Select * From [Order Details Extended] needs ~6msec. > >Using Explain, it showed that in case we run against the >ViewNames, the CoRoutine-approach was present, whereas when >running the SQL directly (and faster), the CoRoutine-preparation >was absent from the Explain-Output... > >No biggie here so far - but reporting the behaviour early seemed >like a good idea to me... > >Kind Regards, > >Olaf > > >_______________________________________________ >sqlite-users mailing list >sqlite-users@mailinglists.sqlite.org >http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
