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Sybase IQ Questions

Posted on 2013-01-28
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Last Modified: 2013-02-07
Hi

It would be a great help if anybody knows the answer for the following queries :

1. In a Sybase IQ Multiplex environment, which process synchronize the secondary nodes using TLV log.

2. In a column with FP index, where and how  the row ids are maintained?   How about in column with LF index?

3. Does the LF index  get rebuilt after loading the data?

thanks
CS
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Question by:ncshome170
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by:Joe Woodhouse
ID: 38830498
1) Every write server (if there is more than one) is in charge of distributing its writes through Table Level Versioning (TLV) Log. This lets the secondary servers know about table versions. Remember IQ effectively locks a table snapshot (although it doesn't copy the whole table, just the changed blocks). TLV in Multiplex is just like the Lock Manager in any traditional RDBMS. You get one of these per writer node.

2) The data is the FP index. There is always an FP on every column because that's where the column's data lives. The ROWID on every column is just the array entry. Remember IQ stores everything in columns, there is actually no real "row" anywhere. "Row #10" just means "the 10th entry in the FP array of column1 + the 10th entry in the FP array of column2" and so on. Is that making sense? The ROWID is not stored anywhere, just as the number of each array entry is also not stored anywhere, it is the data structure.

3) Every index is rebuilt during loads. Unlike traditional RDBMS, it is faster to index an empty table then load it than the other way around. Test it and see. :)
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by:ncshome170
ID: 38838166
Thanks Joe.

Whenever the failed secondary nodes comes back online, there is an internal process which will read TLV log from IQ store and sync the catalog store of that secondary node. Am I right?

Now I understand the ROWID concept in FP index . What about in LF index, is the ROWID attached to LF index column values?

Regards
CS
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Joe Woodhouse earned 500 total points
ID: 38839219
TLV doesn't sync Catalog Store, that holds database schema and the coordinating server syncs that to all other nodes.

TLV is only for table versions, i.e. locking... and after a complete failure or shutdown there are no locking issues to deal with because nothing is running.

If only one node has failed, TLV Log makes sure every node understands which tables are versioned in the writer(s). So yes, automatic, but nothing to do with Catalog Store.

ROWID is only part of the FP index because only the FP has the actual data. LF (and every other index type) does not store the actual data, just additional index structures. That said yes there has to be some kind of internal address associating all the column entries belonging to the same row - maybe they use ROWID, I don't know, but it doesn't make sense to talk about ROWID stored anywhere but in the FP but that's the only place data is stored.

I hope that's making sense, IQ is a bit topsy-turvy. :)
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by:ncshome170
ID: 38863256
Thanks Joe.

Regards
CS
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