I have a trigger in Oracle. Can anyone please help me with how it can be replicated to Redshift? DynamoDB managed stream kind of functionality will also work.
Redshift does not support triggers because it's a data warehousing system which is designed to be able to import large amounts of data in a limited time. So, if every row insert would be able to fire a trigger the performance of batch inserts would suffer. This is probably why Redshift developers didn't bother to support this and I agree with them. The trigger type of behavior should be a part of business application logic that runs in OLTP environment and not the data warehousing logic. If you want to run some code in DW after inserting or updating data you have to do it as another step of your data pipeline.
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Would like some suggestions on loading data to Redshift.
Currently we have an EMR cluster where RAW data is ingested regularly. We have a transformation job which runs daily and creates final modeled object. However, we are following truncate and load strategy in EMR . Due to business reasons there is no way to figure out which data has changed.
We are planning to store of this modeled object in Redshift.
Now my question is If we follow the same truncate and load strategy in
RedShift also, will that work?
I was able to find only articles which say use copy if you want to perform bulk copy, and then use insert command for small updates. But nothing on can and should we be using RedShift where the data is getting overwritten daily.
At my organization, we are using a stack of AWS S3, AWS Glue, and Athena to drive some reporting of internal metrics. In general, this stack is great for quick set up for reporting off of raw data (stored in S3). The problem we've come against is what to do if we notice we need to somehow update the data that's already stored in S3. For example, we want to update values in a column that have a certain string to update that value.
Unlike a database, we can't just run a query to update all the existing data. I've tried to see if we can utilize Glue Jobs to accomplish this, but from my limited understanding, it doesn't seem like it's meant to do ETL from a bucket back to the same bucket.
The only thing I can think is to write a custom tool that iterates through an S3 bucket, loads a file, provides the transformation, and puts it back, overwriting the original. It seems there has to be a better way though.
Updates are not handled in a native way in a traditional hive-like warehousing solution, which I deem Athena to be. A common solution is a kind of engineering workaround where you do "insert overwrite" a partition (borrowing Hive syntax, possible in Presto and hopefully also possible in Athena, which is based on Presto).
Other solutions include creating new tables and atomically replacing a view, which users are supposed to query, instead of querying the underlying table(s) directly.
As this is a common problem, there are also some ready to use solutions to it, but I do not know whether which/whether they are possible with Athena. They are certainly possible with Presto (Presto SQL):
Hive ACID transactional tables (updates currently required Hive runtime)
Data Lake (open sourced by Databricks; updates currently require Spark runtime)
Hudi (I know little about this one)
Under 3 nodes using redshift we plan on doing 50-100 inserts every 10 seconds. Within that 10 second window we also will try to do the equivalent of a redshift upsert as documented here https://docs.aws.amazon.com/redshift/latest/dg/c_best-practices-upsert.html on about 50 to 100 rows as well.
I'm basically unaware if a 10 second window is realistic or a 10 minute window... etc is good for this kind of load. Should this be a daily batch? Should I try to re-architect to get rid of upserts?
My question is essentially can redshift handle this load? I feel the upsert is happening too many times. We are using structured streaming in spark to handle all of this. If yes what type of nodes should we be using? Has anyone who has done this have a ballpark estimate? If no, what are alternative architectures?
Essentially what we're trying to do is load entity data to be joined with the events in redshift. But we want the analytics to be as near real time as possible so we want load as fast as we can.
There's probably no exact answer for this, so any explanation that can get help me perform estimations on requirements based on load will be helpful.
I do not think you will achieve the performance you seek.
Running large numbers of INSERT statements is not an optimal way to load data into Amazon Redshift.
The best way is via running COPY from data stored in Amazon S3. This loads data in parallel across all nodes.
Unless you have a very real need to get data immediately into Redshift, it would be better to batch the data in S3 over a period of time (the larger the batch, the better), then load via COPY. This will also work well with the Staging Table approach to performing UPSERTS.
The best way to discover whether Redshift will handle a particular load is to try it! Spin up another cluster and try the various methods, measuring the performance each time.
I would recommend using Kinesis Firehose to insert data to Redshift. It will optimize for time / load and insert accordingly.
We tried inserting manually in batches, does not seems to be the cleaner way of handling it when an optimized cloud service exist for the same.
https://docs.aws.amazon.com/ses/latest/DeveloperGuide/event-publishing-redshift-firehose-stream.html
It does collect them in batches, compress and load them to Redshift.
Upsert Process:
If you want an upsert this is how I would have them done in a scalable way,
DynamoDB Table (Update) --> DynamoDB Streams --> Lambda --> Firehose --> Redshift
Have a scheduled job to cleanup any duplicate records based on created_timestamp.
Hope it helps.
My team is attempting to use Redshift to consolidate information from several different databases. In our first attempt to implement this solution, we used Kinesis Firehose to write records of POSTs to our APIs to S3 then issued a COPY command to write the data being inserted to the correct tables in Redshift. However, this only allowed us to insert new data and did not let us transform data, update rows when altered, or delete rows.
What is the best way to maintain an updated data warehouse in Redshift without using batch transformation? Ideally, we would like updates to occur "automatically" (< 5min) whenever data is altered in our local databases.
Firehose or Redshift don't have triggers, however you could potentially use the approach using Lambda and Firehose to pre-process the data before it gets inserted as described here: https://blogs.aws.amazon.com/bigdata/post/Tx2MUQB5PRWU36K/Persist-Streaming-Data-to-Amazon-S3-using-Amazon-Kinesis-Firehose-and-AWS-Lambda
In your case, you could extend it to use Lambda on S3 as Firehose is creating new files, which would then execute COPY/SQL update.
Another alternative is just writing your own KCL client that would implement what Firehose does, and then executing the required updates after COPY of micro-batches (500-1000 rows).
I've done such an implementation (we needed to update old records based on new records) and it works alright from consistency point of view, though I'd advise against such architecture in general due to bad Redshift performance with regards to updates. Based on my experience, the key rule is that Redshift data is append-only, and it is often faster to use filters to remove unnecessary rows (with optional regular pruning, like daily) than to delete/update those rows in real-time.
Yet another alernative, is to have Firehose dump data into staging table(s), and then have scheduled jobs take whatever is in that table, do processing, move the data, and rotate tables.
As a general reference architecture for real-time inserts into Redshift, take a look at this: https://blogs.aws.amazon.com/bigdata/post/Tx2ANLN1PGELDJU/Best-Practices-for-Micro-Batch-Loading-on-Amazon-Redshift
This has been implemented multiple times, and works well.
I have a web app that needs to send reports on its usage, I want to use Amazon RedShift as a data warehouse for that purpose,
How should i collect the data ?
Every time, the user interact with my app, i want to report that.. so when should i write the files to S3 ? and how many ?
What i mean is:
- If do not send the info immediately, then I might lose it as a result of a connection lost, or from some bug in my system while its been collected and get ready to be sent to S3...
- If i do write files to S3 on each user interaction, i will end up with hundreds of files (on each file has minimal data), that need to be managed, sorted, deleted after been copied to RedShift.. that dose not seems like a good solution .
What am i missing? Should i use DynamoDB instead, Should i use simple insert into Redshift instead !?
If i do need to write the data to DynamoDB, should i delete the hold table after been copied .. what are the best practices ?
On any case what are the best practices to avoid data duplication in RedShift ?
Appreciate the help!
It is preferred to aggregate event logs before ingesting them into Amazon Redshift.
The benefits are:
You will use the parallel nature of Redshift better; COPY on a set of larger files in S3 (or from a large DynamoDB table) will be much faster than individual INSERT or COPY of a small file.
You can pre-sort your data (especially if the sorting is based on event time) before loading it into Redshift. This is also improve your load performance and reduce the need for VACUUM of your tables.
You can accumulate your events in several places before aggregating and loading them into Redshift:
Local file to S3 - the most common way is to aggregate your logs on the client/server and every x MB or y minutes upload them to S3. There are many log appenders that are supporting this functionality, and you don't need to make any modifications in the code (for example, FluentD or Log4J). This can be done with container configuration only. The down side is that you risk losing some logs and these local log files can be deleted before the upload.
DynamoDB - as #Swami described, DynamoDB is a very good way to accumulate the events.
Amazon Kinesis - the recently released service is also a good way to stream your events from the various clients and servers to a central location in a fast and reliable way. The events are in order of insertion, which makes it easy to load it later pre-sorted to Redshift. The events are stored in Kinesis for 24 hours, and you can schedule the reading from kinesis and loading to Redshift every hour, for example, for better performance.
Please note that all these services (S3, SQS, DynamoDB and Kinesis) allow you to push the events directly from the end users/devices, without the need to go through a middle web server. This can significantly improve the high availability of your service (how to handle increased load or server failure) and the cost of the system (you only pay for what you use and you don't need to have underutilized servers just for logs).
See for example how you can get temporary security tokens for mobile devices here: http://aws.amazon.com/articles/4611615499399490
Another important set of tools to allow direct interaction with these services are the various SDKs. For example for Java, .NET, JavaScript, iOS and Android.
Regarding the de-duplication requirement; in most of the options above you can do that in the aggregation phase, for example, when you are reading from a Kinesis stream, you can check that you don't have duplications in your events, but analysing a large buffer of events before putting into the data store.
However, you can do this check in Redshift as well. A good practice is to COPY the data into a staging tables and then SELECT INTO a well organized and sorted table.
Another best practice you can implement is to have a daily (or weekly) table partition. Even if you would like to have one big long events table, but the majority of your queries are running on a single day (the last day, for example), you can create a set of tables with similar structure (events_01012014, events_01022014, events_01032014...). Then you can SELECT INTO ... WHERE date = ... to each of this tables. When you want to query the data from multiple days, you can use UNION_ALL.
One option to consider is to create time series tables in DynamoDB where you create a table every day or week in DynamoDB to write every user interaction. At the end of the time period (day, hour or week), you can copy the logs on to Redshift.
For more details, on DynamoDB time series table see this pattern: http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GuidelinesForTables.html#GuidelinesForTables.TimeSeriesDataAccessPatterns
and this blog:
http://aws.typepad.com/aws/2012/09/optimizing-provisioned-throughput-in-amazon-dynamodb.html
For Redshift DynamoDB copy: http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/RedshiftforDynamoDB.html
Hope this helps.
Though there is already an accepted answer here, AWS launched a new service called Kinesis Firehose which handles the aggregation according to user defined intervals, a temporary upload to s3 and the upload (SAVE) to redshift, retries and error handling, throughput management,etc...
This is probably the easiest and most reliable way to do so.
You can write data to CSV file on local disk and then run Python/boto/psycopg2 script to load data to Amazon Redshift.
In my CSV_Loader_For_Redshift I do just that:
Compress and load data to S3 using boto Python module and multipart upload.
conn = boto.connect_s3(AWS_ACCESS_KEY_ID,AWS_SECRET_ACCESS_KEY)
bucket = conn.get_bucket(bucket_name)
k = Key(bucket)
k.key = s3_key_name
k.set_contents_from_file(file_handle, cb=progress, num_cb=20,
reduced_redundancy=use_rr )
Use psycopg2 COPY command to append data to Redshift table.
sql="""
copy %s from '%s'
CREDENTIALS 'aws_access_key_id=%s;aws_secret_access_key=%s'
DELIMITER '%s'
FORMAT CSV %s
%s
%s
%s;""" % (opt.to_table, fn, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY,opt.delim,quote,gzip, timeformat, ignoreheader)
Just being a little selfish here and describing exactly what Snowplow ,an event analytics platform does. They use this awesome unique way of collecting event logs from the client and aggregating it on S3.
They use Cloudfront for this. What you can do is, host a pixel in one of the S3 buckets and put that bucket behind a CloudFront distribution as an origin. Enable logs to an S3 bucket for the same CloudFront.
You can send logs as url parameters whenever you call that pixel on your client (similar to google analytics). These logs can then be enriched and added to Redshift database using Copy.
This solves the purpose of aggregation of logs. This setup will handle all of that for you.
You can also look into Piwik which is an open source analytics service and see if you can modify it specific to your needs.