Category: AzureDWH

Benchmarking , Snowflake, Databricks , Synapse , BigQuery, Redshift , Trino , DuckDB and Hyper using TPCH-SF100

(Disclaimer : I use BigQuery for a personal project and it is virtually free for smaller workload, at work we use SQL Server as a Data Store, I will try my best to be objective )

TL:DR ;

Run TPCH-SF100 benchmark (base table 600 million rows) to understand how different Engine Behave in this workload using just the lowest tier offering, you can download the results here

Introduction

Was playing with Snowflake free trial ( maybe for the fifth time) and for no apparent reason, I just run Queries on TPCH-S100 Dataset, usually I am interested in smaller dataset, but I thought how Snowflake may behave with bigger data using the smallest cluster, long story short, I got 102 second, posted it in Linkedin and a common reaction was Snowflake is somehow cheating.

Obviously I did not buy the cheating explanation , as it is too risky and Databricks will make it international news.

Load the Data Again

Ideally I would have generated the Data myself and load it into Snowflake, generating 600 Million records in my laptop is not trivial, my tool of choice, DuckDB has an utility for that but it is currently single threaded, instead

  • I exported the data from Snowflake to Azure Storage as parquet files
  • Download it to my Laptop, generate new files using DuckDB as in Snowflake you can’t control the minimum size of files, you can control the max but not the Min

Snowflake Parquet External Table

My Plan was to run Queries directly on Parquet hosted on azure storage, the experience was not great at all, Snowflake got Query 5 join order wrong

Snowflake Internal Table

I loaded the parquet files generated by duckdb, Snowflake getting extremely good results. what I learnt, whatever Snowflake magic is doing, it is related to their proprietary file format.

BigQuery External Table

I have no frame of reference for this kind of workload, so I loaded the the data to BigQuery using external table in Google Cloud, Google got 5 minutes, one Run, 2.5 $ !!!!

BigQuery Internal Table

Loaded Data to BigQuery internal format, notice, BigQuery don’t charge for this operation , 2 Minutes 16 second, 1 Cold Run.

BigQuery Standard Edition

BigQuery added new pricing model where you pay by second, after the first minutes, I used the Standard Edition with a small size, I run the same query two time, unfortunately the new distributed disk cache don’t seems to be working, same result 5 minutes, that’s was disappointing

Redshift Serverless

Imported the same Parquet files into Redshift serverless, The schema was defined without Distribution keys, The results are for 3 Runs, the first run was a bit slower as it is fetching the data from the managed storage to the compute SSD the other 2 runs are substantially faster, I thought it is fair to have an average, Using the lowest Tier 8 RPU (2.88 $/Hour)

Redshift Serverless hot run was maybe the fastest performance I have seen so far, but they need still to improve on their cold Run.

I was surprised by the system overall performance, from my reading, it seems AWS basically rewrite the whole thing including separating compute from storage, Overall I think it is a good DWH.

Trino

Trino did not run Query 15, had to run a modified syntax but same results, 1 Run from Cold Storage, I am using the excellent service from Starburst Data

Synapse Serverless

Honestly, I was quite surprised by the performance of synapse serverless, initially I tested with the smaller file size generated by Snowflake and it did work, the first run failed but the second works just fine, I did like it, it did failed quickly, notice that Synapse run statistics on parquet files, so you would expect a more stable performance, not the fastest, but rather resilient.

Anyway , it took from 8-11 minutes, to be clear that’s not Synapse from two years ago.

Not related to the benchmark but I did enjoyed the lake database experience

Databricks External Table

I had not a great experience with Databricks, I could not simply pass authentication to Databricks SQL, you need a service principal and registering an App, and the documentation keep talking about Unity, which is not installed by default, This is a new install why Unity is not embedded if it is such a big deal ?

Anyway, First I created an external Table in databricks using the excellent passthrough technique in the Single Node Cluster, Databricks got 12 minutes,

Databricks Delta table

let’s try again with Delta, I created a new managed table, run optimize and analyse , (I always thought delta has already the stats), but it didn’t seems to make a big difference, still around 11 minutes, and this running from the disk, so no network bottleneck

DuckDB

My Plan was to run DuckDB on Azure ML, but I need a bigger VM than the one provided by default, I could not find a way to increase my Quota , I know it sounds silly, and I am just relating my experience, turn out Azure ML VM Quota is different from Azure VM, it did drive me crazy why I could get any VM in Databricks but Azure ML keep complaining I don’t have enough CPU.

Unfortunately I hit two bugs, first the native DuckDB file format seems to generate double the size of Parquet, the dev was very quick to identify the issue, the workaround is to define the table schema and then load the data using insert, the file became 24 GB compared to the original 40GB parquet files.

I End Up going with parquet files, I was not really excited by loading a 24 GB file in a storage account.

I run the Queries in Azure Databricks VM E8ds_v4 (8 cores and 64 GM of RAM)

As I am using fsspec with disk cache, the remote storage is used only the first run, after 4 tries, Query 21 keep crashing the VM šŸ˜¦

Tableau Hyper

Tableau hyper was one of the biggest surprise, unfortunately, I hit a bug with Query 18, otherwise, it would have being the cheapest option.

Some Observations

  • Initially I was worried I made a mistake in Snowflake results, the numbers are just impressive for a single node tier, one explanation is the Execution Engine is mostly operating on compressed data with little materialization , but whatever they are doing, it has to do with the internal table format, which bring a whole discussion of performance vs openness, personally in a BI scenarios, I want the best performance possible, and wonder if they can get the same speed using Apache Iceberg.
  • Synapse Serverless improved a lot from last year, it did work well regardless of the data size of individual parquet files that I throw at it, and in my short testing it was faster than databricks and you pay by data scanned, so strictly speaking pure speed is not such a big deal but without a free result cache like BigQuery, it is still a hard sell.
  • Azure ML Quota policy was very confusing to me, and honestly I don’t want to deal with support ticket.
  • Databricks; may well be the fastest to run 100 TB, but for 100 GB workload, color me unimpressed.
  • DuckDB is impressive for an open source project that did not even reach version 1. I am sure those issues will be fixed soon.
  • Everything I heard about Redshift from twitter was wrong, it is a very good DWH, with Excellent performance.
  • BigQuery as I expected has excellent performance both for parquet and the native table format, The challenge is to keep the same using the new auto scale offering. added Auto scale performance, I think Google should do better.

Summary Results

You can find the results here, if you are a vendor and you don’t like the results feel free to host a TPCH-SF100 dataset in your service and let people test it themselves.

Note : Using SQL Query History : Bigquery one Cold Run , Synapse Serverless , Redshift Serverless and Snowflake a mix of cold and warm

(Note : Synapse Serverless always read from remote storage)

Databricks I am showing the best run from Disk, there is no system table, so I had to copy paste the results from the console.

Pricing

I did not kept the durations for Data load, it is just the cost for Read, obviously it is a theoretical exercise, and does not reflect real life usage which depends on other factors like concurrency performance , how you can share a pool of resources to multiple departement,free results cache, the performance of your ODBC drivers etc.

it is extremely important to understand what’s included in the basic price, for example.

Results cache:

BigQuery, Snowflake, Redshift results cache are free and you don’t need a running cluster, in Databricks you pay for it, Synapse don’t offer result cache at all.

Data loading :

BigQuery data loading is a free operation and other service like sorting and partitioning, in other DB you needs to pay.

Egress Fees :

Snowflake/BigQuery offer free egress fees, Other vendors you may pay, you need to check

Note :

BigQuery : for This workload make more sense to pay by compute not data scanned, either using auto scale, reserved pricing etc, I will try to test Auto scaling later.

Snowflake : I used the standard edition of Snowflake

Edit : I used a Google Colab notebook with a bigger VM for Hyper and DuckDB, see full reproducible notebook

Final Thoughts

Cloud DWH are amazing tech and only competition can drive innovation, not FUD and dishonesty, regardless of what platform you use, keep an eye on what other vendors are doing, and test using your own workload, you may be surprised by what you find.

PowerBI Hybrid Table, you can have your cake and Eat it too.

Hybrid table is a Clever technical solution to a very fundamental problem in Data Analytics, How to keep Data fresh and at the same time fast, PowerBI , Tableau, Qlik solved this problem by importing data to a local Cache, this solution work for most of the use cases, but as with any solution it has limitation.

  • If the Data Source is too big, you can’t simply keep importing to the local cache.
  • If the Data Source change very frequently, like every couple of minutes or second, importing become just not practical or very hard.

PowerBI Engine team came up with a very simple Idea, you can have both Mode in the same table, Historical data that don’t change is cached and today data is queried live as it changed very quickly, Patrick from Guy in the Cube has a great video , Andy has another Video but specific to Synapse Serverless

This functionality was released in the December 2021 edition of PowerBI , but unfortunately when I test it with BigQuery, it did not work, I reported the issue and I have to say, I was really impressed by the Product team, (Kudos to Christian Wade and Krystian Sakowski ), yesterday they released an updated version and it fixed the issue. (it works with Snowflake, Databricks etc)

Setup

it is literary just an extra box to click compared to the Previous incremental refresh User interface

Yes, Just like that, The Engine will generate table partitions behind the scene, if you want to know why PowerBI is so successful, it is because of stuff like this, take a very hard problem and make it extremely easy for Non Tech people to use.

The Data Model is very simple; one fact table with Data that change every couple of minutes, and a Date dimension in a Mixed mode, ( watch Patrick Video, he explain why)

Premium Only

Yes, it is a premium only feature, and obviously it works with Premium per User, I am not going to complain, someone needs to pay for those R&D cost, but it will be really nice if they release it to the PRO license too, it just feels Odd that a core feature of the Engine is tied to a particular license, we had this situation before with incremental refresh and they did release it even for the free license, I hope the same will happen with Hybrid Table.

Mixed Partitions

I published the report to the service, and used Tabular Editor to see what’s going on behind the scene (make sure you download the latest version of Tabular Editor, works with the free version too)

Image

As expected the Last Partition is Live Mode, and everything else is cached in PowerBI.

How it Works

I used DAX Studio to capture what the engine is doing when you run a Query

Image

PowerBI formula engine send two Queries one to the remote DB in my case BigQuery and the local Storage, you can clearly see the difference in speed

1 Day using DQ : 2 second ( the Query take 400 ms at the end point, But BigQuery has a very substandard ODBC driver)

13 Months worth of Data Cached : 47 ms

The Point is, if you can just import, do it, you will get the best performance and user experience

( At Work we have a sub 5 minute pipeline end to end from the Source DB to PowerBI).

The Devil is in the details

As far as I can tell, Formula Engine keep sending two Queries every time, even when the required data is cached already, obviously the Query from the external DB will return null results, in Theory , it should not be a big deal, Modern DW are fast specially with partitioning pruning.

Unfortunately no, only some Database can return a sub second null result set to PowerBI ( yes the Quality of the Driver is as important as the DB Engine itself)

Take Away

It is a very interesting solution worth testing for specific scenarios, but if you can get away with Importing data only, then it is still the best way, yes Hybrid Table reduce the Workload on the remote Database, but still you need a solid Database, getting a sub second Query from end to end is still a hard problem even for 1 day worth of data ( just test it, don’t forget concurrency )

I heard a different use cases, which I find very intriguing, some users want the other way around, recent Data as Import and historical Data as Direct Query, I guess it is useful if you have a real big fact Table.

A Surprising side effect of PowerBI Hybrid table,( maybe it was planned, who knows) Synapse Serverless in Direct Query mode looks now like a very good candidate to use, scanning one day of data is faster and an order of magnitude cheaper !!!

I still Hope that the Vetipaq Engine team surprise us in a future update and somehow let the Formula engine generate only 1 Query when all Data needed is in the Local cache.

Benchmarking Synapse Serverless using TPC-H-SF10

Edit : February 2023 , Synapse serverless has substantially improved the Query performance for TPCH-SF10, first run which include calculating the statistics take around 2 minutes, but the second run is around 62 second.

In a previous blog, I did a benchmark for a couple of Database Engine, although it was not a rigorous test, pretty much the results were in the expected range, except for Synapse serverless, I got some weird results, and not sure if it is by design or I am doing something very wrong, so I thought it worth showing the steps I took hoping to find what’s exactly going on. The test was done in January 2022.

First Check : Same region

I am using an azure storage in Southeast Asia

My synapse Instance is in the same region

Ok both are in the same region, first best practice.

Loading Data into Azure Data Store

The 8 parquet files are saved in this Google drive, so anyone can download it,

Define Schema

In Synapse, you can directly start querying a file without defining anything, using Openrowset, I thought I can test TPC-H Query 1 as it uses only 1 table, which did not work , some kind of case sensitive issue, when writing this blog I run the same Query and it worked just fine, ( no idea what changed)

1 minute on a second run, hmm not good, let’s try a proper external table , the data_source and File_format were already defined, so need to recreate it again.

CREATE EXTERNAL TABLE lineitem_temp (
	[L_ORDERKEY] bigint,
	[L_PARTKEY] bigint,
	[L_SUPPKEY] bigint,
	[L_LINENUMBER] bigint,
	[L_QUANTITY] float,
	[L_EXTENDEDPRICE] float,
	[L_DISCOUNT] float,
	[L_TAX] float,
	[L_RETURNFLAG] nvarchar(1),
	[L_LINESTATUS] nvarchar(1),
	[L_SHIPINSTRUCT] nvarchar(25),
	[L_SHIPMODE] nvarchar(10),
	[L_COMMENT] nvarchar(44),
	[l_shipdate] datetime2(7),
	[l_commitdate] datetime2(7),
	[l_receiptdate] datetime2(7)
	)
	WITH (
	LOCATION = 'lineitem.parquet',
	DATA_SOURCE = [xxx_core_windows_net],
	FILE_FORMAT = [SynapseParquetFormat]
	)
GO


SELECT count (*) FROM dbo.lineitem_temp
GO

A Proper Table with Data type and all

let’s try again the same Query 1

ok 2 minute for the first run, let’s try another run which will use statistics, it should be faster, 56 second ( btw, you pay for those statistics too)

Not happy with the results I asked Andy ( Our Synapse expert) and he was kind enough to download and test it, he suggested splitting the file give better performance , he got 16 second.

CETAS to the rescue

Create External Table as Select is a very powerful functionality in Serverless, The code is straightforward

CREATE EXTERNAL TABLE lineitem 
	WITH (
	LOCATION = '/lineitem',
	DATA_SOURCE = [xxxx_core_windows_net],
	FILE_FORMAT = [SynapseParquetFormat]
	)
as
SELECT * FROM dbo.lineitem_temp

Synapse will create a new table Lineitem with the same data type and a folder that contain multiple parquet files.

That’s all what you can do, you can’t partition the table, you can’t sort the table, but what’s really annoying you can’t delete the table, you have first to delete the table from the database then delete the folder

but at least it is well documented

Anyway, let’s see the result now

Not bad at all, 10 second and only 587 MB scanned compared to 50 second and 1.2 GB.

Now that I know that CETAS has better performance, I have done the same for remaning 7 tables.

Define all the tables

First Create an external Table to define the type then a CETAS, Synapse has done a great job guessing the type, I know it is parquet after all, but varchart is annoying by default it is 4000, you have to manually adjust the correct length.

TPC-H document contains the exact schema

Running the Test

The 22 Queries are saved here, I had to do some change to the SQL, changing limit to Top and extract year from x to Year (x), Query 15 did not run, I asked the Question on Stackoverflow and Wbob kindly answer it very quickly

The first run, I find some unexpected results

I thought I was doing something terribly wrong, the Query duration seems to increase substantially, after that I start messing around, what I found is, if you run just one Query at the time, or even 4, the results are fine, more than that, and the performance deteriorate quickly.

A Microsoft employee was very helpful and provided this script to Query the Database History

I imported the Query History to PowerBI and here is the results

There is no clear indication in the documentation that there is a very strict concurrency limitation, I tried to run the Script in SSMS and it is the same behavior, that seems to me the Engine is adding the Queries to a queue, there is a bottleneck somewhere.

Synapse serverless show the duration between when the Job was submitted until it is completed, there is no way to know the actual Duration of each Query, so basically the Overall Duration is the duration of the Last Query, in our Case Q22, which is around 3 Minutes.

Takeway

The Good news, the product team made it very clear, Synapse Serverless is not an Interactive Query Engine

Realistically speaking, reading from Azure storage will always be slower compared to a local SSD Storage, so no I am not comparing it to other DWH offering, having said that even for exploring files on azure storage, the performance is very problematic.

First Look at SingleStore

I could have written a nice paragraph why I got interested in SingleStore but to be honest the reason is very simple and has nothing about the tech, Jordan Tigani one of the founding Engineers of BigQuery is now their Chief Product Officer, so I became very curious šŸ™‚

Again, I am only interested in Small Interactive BI Workload, contrary to the usual Suspects ( BigQuery, Snowflake etc), SingleStore is not a pure Data warehouse but rather a multi purpose database, it does OLTP Workloads but has an excellent support for OLAP Workload, I am only interested in Analytical Workloads.

Setup

There is a free trial with $500, the setup was very intuitive, I really liked the way you create a new Cluster, notice I don’t have an account with AWS, but it is a software as a service Experience, SingleStore manage everything on behalf of the user, I chose AWS as they support the Sydney Region.

The smallest tier start at 0.25 Credit/hour, which cost 0.65 $/Hour, Unlike Snowlake and Databricks there is no auto suspend and auto start, you have to do it manually.

For some reason Suspend a Cluster is not available in Google Cloud !!!

The Console has the bare minimum but functional, there is no multiple tab, if you run a Query, you need to wait till it is done before running another one

There is an odd choice in the UI, when you want to monitor the Cluster you need to open a new page called SingleStore Studio

It is not the end of the world, but a bit annoying when you are new to the product

Loading Data

There is sample Data you can quickly load to start running Queries, but I wanted to test only my own dataset (TPC-H- SF10) ( nice surprise it was added this week)

Although my Cluster is in AWS, loading files from Google Cloud was trivial, all I had to do is setup a new pipeline

first define the table, notice the Clustered Columnstore key

CREATE TABLE `orders` (
`o_orderkey` bigint(11) NOT NULL,
`o_custkey` int(11) NOT NULL,
`o_orderstatus` char(1) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`o_totalprice` decimal(15,2) NOT NULL,
`o_orderdate` date NOT NULL,
`o_orderpriority` char(15) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`o_clerk` char(15) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`o_shippriority` int(11) NOT NULL,
`o_comment` varchar(79) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
SHARD KEY (`o_orderkey`) USING CLUSTERED COLUMNSTORE
);

Define a new pipeline

CREATE or REPLACE PIPELINE `LoadGCPorders`
AS LOAD DATA GCS 'xxxxxxxxxxxxx'
CREDENTIALS '{"access_id": "xxx", "secret_key": "xxxxxx"}'
INTO TABLE tpch.orders
(`O_ORDERKEY` <- `O_ORDERKEY`,
  `O_CUSTKEY` <- `O_CUSTKEY`,
  `O_ORDERSTATUS` <- `O_ORDERSTATUS`,
  O_TOTALPRICE <- O_TOTALPRICE
  , O_ORDERDATE <- O_ORDERDATE
  , O_ORDERPRIORITY <- O_ORDERPRIORITY
  , O_CLERK <- O_CLERK
  , O_SHIPPRIORITY <- O_SHIPPRIORITY
  , O_COMMENT <- O_COMMENT
  
  )
FORMAT PARQUET

Then Run the pipeline and the data is automatically loaded, very nice

START PIPELINE LoadGCPorders FOREGROUND;

Testing using TPC-H SF10 Benchmark

to test all the 22 Queries of the benchmark I used the same script for BI Engine, here is the results after 10 runs using the Dataset Provided by Singlestore ( Using S-0 Cluster, see pricing here)

A lot of Queries are already under a second even when using a lower tier !!! Queries 13 result is a bit odd.

if I understood correctly, SingleStore does not have a results cache when you run the same Query again, SingleStore store the Query plan but scan the data again, although the data is stored on Disk, metadata on the tables is stored In-Memory ( tables for OLTP workload are always In-Memory)

The Previous chart was built using Google Data Studio, as of this writing, PowerBI does not have a native connector, you need to download a custom connector which means you need a gateway, not sure if Direct Query is supported at all, I quickly used MySQL connector which works fine but import mode only (SingleStore is compatible with MySQL tools)

Take Away

I was really impressed by the Product, we all hear about this operational analytics and it seems SingleStore has a good solution, there are missing functionalities though, Auto suspend and resume is not available yet and no native connector for PowerBI is very problematic, but it is really Fast and do write workload too.