Ratcl wiki: Questions - *** THIS FORUM IS ARCHIVED ***

Got a question about Ratcl? I'll answer on this page... -jcw

Posted at Feb 03/2004 01:32 PM:
jcw: In [link], LV asks about joins and set operators:

Relational join:

T join1 U: each row in T is joined to matching U's, if no U's match, that T row is not in the result
T join0 U: each row in T for which there is no matching U
join1 is not set intersection (T and U columns are usually not the same)

Note that if T and U have columns C and D in common (as in the intro), then "T join0 U" is equivalent to:

    T join1 [[T project {C D}] except [U project {C D}]]

Set operators:

input views must be sets (no duplicate rows), result is also a set

Posted at Feb 03/2004 02:05 PM:
LV: In the operation T join1 U are all columns being used as the join point, or is it only the first column?

Posted at Feb 03/2004 02:12 PM:
jcw: the columns which have the same name

Posted at Apr 16/2004 06:13 AM:
atp: Ratacl seems exceedingly interesting. Could it eventually work with the Tcl Threads Extension to give us a highly-concurrent, in-memory RDBMS? That would be VERY useful!

Interesting idea - I don't see why not. The data is meant to be kept in Ratcl, not Tcl, so all it would take is a mutex-protected flavor of the extension to reach the same data structures. I'll ponder a bit more on this, thx for the suggestion -jcw

Posted at Apr 16/2004 09:26 PM:
atp: What about higher-dimension "views"? Could Ratcl views be used as 3, 4, or more dimensional matrices, rather than 2D only?

There are two ways to bring in dimensions: with sliced indexing and ranks as in APL and Fortran, and with nested data structures as in Tcl itself (and the Metakit DB). Note that Ratcl is not really 2D: the horizontal and vertical dimensions play distinct roles. I'm more inclined to see Ratcl as 1-dimensional with structures. My hope would be that 2D/3D/etc would be an extension of the row-wise dimension, while still supporting structures. Extending into more dimensions is not at the top of my list right now, one reason being that Ratcl's performance levels are still far from where I need them to be -jcw