I am currently having a lot of pain with getting data into Power BI. I have a query that I use to get data from a SQL view. When you open Advanced editor when transforming the data you can see the select statement.
Now I thought this would be classed as a native query. But when I right click on the Source step Native Query is not on the context menu?
The query seems to be very slow.
If you open advanced editor you get
let
Source = Sql.Database(“Instance”,“DB”,[Query = SELECT col1,col2,…coln from v_someview" ,createNavigationProperties = false, CommandTimeout=#duration(0,4,0,0])
This is used against three views each one has circa 5 m rows.
I have no control over the view so I can not change the SQL or remove columns etc. This is why I am using a Query.
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Hi ells!
Instead of looking at Advanced Editor, you can click on the gear icon next to Source. That will open up a window to paste in an actual query against the View. I have written queries in SQL and pasted them right in. You can join Views, Tables, etc. You can use SubQueries, CTE’s, etc. The tables I deal with are huge - and I am coming from a SQL background, so it’s easier for me to use my own queries.
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@TonyaM
Thanks. I have just read what I posted. I am looking for query performance. Thanks I will look at that as it has got to be easier to read.
I have a similar background. I am struggling in that 15m rows will take longer than 5 hours to load. I am pretty sure it is the SQL Server that is the issue and looking at Query execution plans but if there is anything I am doing wrong in Power BI I want to correct that.
Hi @ells. When I encounter a performance issue getting data from SQL Server, I use the same query in SQL Server Management Studio and check the database server’s execution plan and optimize the query there first; Power Query is unlikely to be able to do much to make a slow query faster. Would it be possible to reduce the amount of data retrieved by the query (fewer rows, fewer columns, integer keys instead of string or date/time values, etc.)?
Greg
@Greg
Thanks.
Cant reduce the amount of data. I am not even retrieving half of what the users want. In all honsesty the voulmes dont seem to be the issue. Sure there is 15M rows and with a lot of dimensions there are some 15 foreign keys.
On the SQL side the query runs in 15monutes for each 5M row chunks. However when loading into Power BI desktop to build the data set this fails after 5 hours - due to timeout.
SQL is controlled by another company so waht I can achieve is limited. I can see some issues but they dont make the inroads that I need, There are a couple of Hash Matches which I have not come across before.
I can see the laptop I am using is struggling (common to see CPU and memory hit 90% or more), can also see the disk filling up so assume it is spooling to disk.
I am going to give it a go sticking the fact in a data flow. Although if that works then we may have some issue with security so not ideal.
@Greg
I spent a bit of time yesterday looking further into this. I decided to create a data flow and see how that performs. Went and refreshed it with 4 years of data. Came back an hour later and ut had completed the refresh.
It appears that the combination of laptop and Powewr BI desktop are causing the issue.
Does it load the data from SQL to memory When I have clicked ‘close and apply’ this is the point it pauses and struggles?
Yes … when transforming your data, only schema and a subset preview are loaded into the model … as you said, it’s when you hit “close-and-apply” that all of the data is loaded into the model. Glad it’s now better for you. Greg
Hi @ells. Just a thought … have you investigated aggregations, as this could potentially vastly reduce your rowcount if your report is going to roll-up results anyway… Greg
@Greg,
I did start to look at it.
i think one of the problems is the number and width of the dimensions. If I did a count of rows on the table, Then did a distinct count based on the foreign keys I am using I would get circa 85% of the total.
I am not sure that Aggregations would work with that sort of percentage?
Have not been able to find any deep knowledgable info on them so have not placed it at the top of the list and as I am struggling to get the data into workflow / model this is where I am focussing.
Thanks
E
revisit the report design and be really specific about the question it is supposed to answer; perhaps it doesn’t need the 30M rows but could “get-away” with a subset
do your rollups in your on-premises data source and only pull the results table into Power BI
I don’t know if one or both of these would be of any help to your situation …
Greg
