topic Re: [resolved] tMap needs to support multiple lookups to the same table (alias) in Talend Studio

[resolved] tMap needs to support multiple lookups to the same table (alias)

Anonymous — Sat, 16 Nov 2024 13:47:56 GMT

In a Data Warehouse Star schema scenario it is a common requirement to be able to lookup multiple surrogate keys based on the same physical lookup table. Example: A (main) order record may contain the following columns: OrderDate, ProcessedDate, ShippedDate, etc - all needing separate surrogates from a date dimension in the data pipeline. Therefore the Date Dimension needs to be used as a lookup multiple times. In OLAP terms this is called a role-playing dimension. In database terms this is just an alias.
So, rather than duplicating the Date dimension table multiple times as mutiple tInput lookup components, and using up memory, it would be great to use a single tInput lookup component, and in the tMap, be able to alias that single input lookup multiple times, joined from the desired main input. That makes for a simpler design, and should save valuable memory.
Dave

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

Anonymous — Fri, 28 Aug 2009 09:04:37 GMT

+1
Thank you for saying out loud !

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

Anonymous — Wed, 30 Sep 2009 16:25:00 GMT

Hi,
It's already exist into our tELTMap you can refer multiple INPUT TABLE for the same using Alias.
Best regards;

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

Anonymous — Wed, 30 Sep 2009 16:40:38 GMT

Hi,
It's already exist into our tELTMap you can refer multiple INPUT TABLE for the same using Alias.
Best regards;

Any way to include that functionality in the non ELT (regular) tMap?
Dave

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

Anonymous — Wed, 07 Oct 2009 18:11:57 GMT

Hi,
It's already exist into our tELTMap you can refer multiple INPUT TABLE for the same using Alias.
Best regards;

Wanted to ask again:
Any way to include that functionality in the non ELT (regular) tMap? We are not using ELT.
Dave

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

amaumont — Thu, 08 Oct 2009 09:09:26 GMT

tHashOuput and tHashInput components exist but they are not official, they don't take account StoreOnDisk mode, and they don't work well when they are directly connected to a tMap.
Yet, I will speak about this subject at our next meeting.

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

Anonymous — Thu, 08 Oct 2009 15:56:10 GMT

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

_AnonymousUser — Fri, 15 Jan 2010 20:01:23 GMT

Is there any solution for this? I have to load 3 times the date and hour tables !!!

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

Anonymous — Fri, 15 Jan 2010 20:09:21 GMT

Is there any solution for this? I have to load 3 times the date and hour tables !!!

Im tMap, you can create a lookup based on the same table more than once, but, essentially, you are incurring the extra memory for each duplicated lookup table, nit to mention cluttering up the job display . Also, if the solution adds inferred dimension members on the fly, and that dimension is on eof the dups, then I would doubt that the others would get get updated. - not sure if Talend dynamically updates lookup cache as records are added.
I am used to SSIS (I like Talend better), where the same lookup table can be aliased several times. Also, added inferred dimension members are dynamically added to the lookup cache as well.
Hopefully talend will jump on this one.
Dave

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

_AnonymousUser — Sat, 16 Jan 2010 01:51:09 GMT

And could you explain to me how can I do that on Tmap component ? Thanks in advance

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

_AnonymousUser — Mon, 18 Jan 2010 09:04:36 GMT

And could you explain to me how can I do that on Tmap component ? Thanks in advance

Anyone ?

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

Anonymous — Thu, 19 Aug 2010 18:14:03 GMT

Hi,
It's already exist into our tELTMap you can refer multiple INPUT TABLE for the same using Alias.
Best regards;

Cantoine,
This actually already works using a regular tMap, I successfully used the same table multiple times in a single tmap. Since Talend automatically aliases each lookup, it just treats each instance like another table - works great.
This would make a great webinar.
Dave

Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

Anonymous — Tue, 31 Aug 2010 19:57:18 GMT

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Re: [resolved] tMap needs to support multiple lookups to the same table (alias)

_AnonymousUser — Mon, 28 Nov 2016 06:56:14 GMT

I am migrating from datastage to talend. I have a requirement where i am performing 200 reference lookups in 3 lookup stages in a set of 70-70-60 per lookup stage. All the reference lookups for each lookup stage are coming from one source, How should this be implemented in Talend as tmap maps one to one amongst its components.