Hi All,
I am trying to do an on disk update for a splayed table something on the lines of
https://code.kx.com/q/ref/lists/#amend
But it keeps on throwing me an 'open error while I use the filehandle for update.
Ex:
@[`:tbl;enlist 2;:;dict]
where dict is the new row.
Can anyone help me in this?
Hey,
To update on disk you can simply upsert to the filepath for example:
q)`:hdb/tab1/ set tab1
`:hdb/tab1/
q)tab1
price size char
1 4 A
2 5 B
3 6 C
q)\l hdb
q)tab1
price size char
1 4 A
2 5 B
3 6 C
q)`:tab1 upsert enlist dict
`:tab1
q)\l tab1
`tab1
q)tab1
price size char
1 4 A
2 5 B
3 6 C
4 5 D
However if you want to update a specific row on disk you could update each column individually with something like:
@'[sv':tab1,'key dict;2;:;value dict]
I wouldn’t really recommed this method as iterating over columns to update them is a particularly bad idea as there is a risk involved in the operation in that it can cause significant issues were it to fail (i.e. a possible corruption of your partition).
Hope this helps!
Seán
On-disk tables are append-only. In order to update an on-disk dataset, you can only read it into memory, amend it, and re-splay the resultant data back to disk.