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Benjamin De Boe · Jan 10, 2023

Nice visionary article!

Luckily we didn't rush this 13 years ago ;-) as the model described in there would offer some benefits, but not get to the order of magnitude performance improvement we're bringing with this new IRIS feature. Organizing data in separate nodes as proposed there may help somewhat to limit the size of each read (read the column value rather than the full row's $list), but you're still doing NxM small grefs to read M columns for N rows. When you're talking billions of rows, that sheer volume of grefs is the bottleneck we saw preventing us from doing really well on analytics queries. 

With Columnar Storage, the new $vector datatype we introduced that encodes 64k values into a single global node offers much better economies on today's hardware, and also enable SIMD instructions on those, which you couldn't get by keeping values in separate variables. Of course introducing all-new datatypes (and especially internal ones like $vector) isn't something you could do using ObjectScript in user code, but I promise we'll offer Key-Value before IRIS 2036.1! :-)

Benjamin De Boe · Nov 10, 2022

For the record: it's not the Abstract-ness that leads to the index being ignored, it's the fact that the index is not defined in the primary superclass of Test.NewClass1. From secondary superclasses, only parameters, properties and methods are inherited, but not indices. So you can keep Test.NewClass Abstract, but make it inherit from %Persistent itself and then have Test.NewClass1 point to it as its primary superclass. I'll ask the doc team to make this a little clearer, as it's not obvious from this section of the doc nor the one on indices right now.

This said, @Robert Cemper 's suggested use of NoExtent is likely what you wanted to achieve.

Benjamin De Boe · Nov 10, 2022

Yes, it always behaved like this. Currently, table stats are stored as part of the class definition, based on the idea that they are often kind of static and belong with the application. That holds for certain types of applications, but in many cases it is a little too static and this is especially true for the Message Bank example here, as TuneTable cannot update class definitions for a read-only system class.

We have a project coming up to move the table stats to live with the data rather than keep them in the class definition and hope to bring that to an IRIS release in the course of 2023. In the meantime, the workaround suggested above, marking ENSLIB as writable, running TT and then marking it read-only again is reasonable (though quite a step from an official recommendation). Note that after upgrades, your ENSLIB will be overwritten and your stats will have been lost.

FYI, the last part of this article also touches on this subject

Benjamin De Boe · Nov 7, 2022

In the case of JDBC, there's also the getGeneratedKeys() method that you may find useful.

We're looking into support for a RETURNING clause for the INSERT command as a possible enhancement (Postgres' flavour of this nonstandard clause is very nice), but don't hold your breath as we have a long list of such candidate enhancements and a much shorter list of people who can work on the surprising amount of places in our codebase that would need to be updated to accommodate such a syntax extension.

Benjamin De Boe · Oct 30, 2022

There is apparently an internal-design-level distinction between UDL as an editor format and XML as an export format. We appear to have closed the case without clarifying the documentation on this point (apologies for this oversight), but I've reopened the case so we might review and reconsider the current behaviour more broadly. There's a number of additional flags like these, so it's possibly a larger change.

Benjamin De Boe · Oct 27, 2022

@Vitaliy Serdtsev is right in pointing to the resultset's metadata. That's where IRIS SQL registers column datatypes and he already pointed out that this is obviously not impacted by the presence of an ORDER BY. 

The resultset object returns the SQL-side value to ObjectScript, but on that ObjectScript side, the datatype no longer matters as it isn't strongly typed and still 1="1". Therefore, I don't think this constitutes an error.

FWIW, the reason you're seeing this is that due to the ORDER BY clause we're picking up that id value from the index' subscript rather than from the master map.

Benjamin De Boe · Aug 30, 2022

Hi Jun, those sandboxes are controlled environments set up for specific courses. There isn't really a course corresponding to this demo / subject, so unfortunately no single-click-install this time. 

Once you have a running instance of IRIS, setting it up through the commands described above shouldn't be that big a deal:

do $system.OBJ.ImportDir("/path/to/downloaded/isc-iknow-setanalysis","*.xml","c",,1)

do ##class(Demo.SetAnalysis.Utils).CreateRestWebApp()
Benjamin De Boe · Aug 22, 2022

Thanks @Vitaliy Serdtsev 

Indeed, that method will be deprecated shortly, in favour of CREATE TABLE AS SELECT, which is new in 2021.1 and part of the SQL standard. Both this command and the $SYSTEM utility method will create a physical copy of the data, so a real SQL table that's not kept in sync in the way a SQL view is. If the latter is what you need, don't bother with creating it as a table.

Note that in a more recent version we also support the CREATE OR REPLACE syntax for a bunch of additional statements (including CREATE FUNCTION, CREATE PROCEDURE, ...) and CREATE IF NOT EXISTS for things that actually contain data such as tables.

Benjamin De Boe · Jul 29, 2022

yeah, while I appreciate @Renato Banzai 's creativity in the above article, I can't resist to make a plug for our %Stream classes that can take care of very large strings. Also, starting 2021.2, Stream data is compressed by default, which can easily save you 80% on storage for content such as XML. I have a couple of utilities here that complement this feature by allowing you to compress old stream data in-place.

Benjamin De Boe · Jul 29, 2022

Cool stuff! For this age-old iKnow demo I used import.io to scrape a bunch of hotel reviews from the web, but it was pretty crude and server-based, so impossible to include in the demo repo. I've heard of beautifulsoup before, but never considered revisiting that data sourcing piece of my demo now that we can use it directly through Embedded Python.

Benjamin De Boe · Apr 29, 2022

I'm not sure what you mean with "linear cost pagination", but as soon as your query plan gets more complex than reading a single stream (and especially when sorting) there is upfront work before you can start reading the first row so any pagination of that final result simply cannot be linear. 

That small disclaimer aside, "customizable filtering and sorting" sound like application-level features you'd apply on top of the result set returned by SQL and the %ScrollableResultSet class offers something along those lines. If you're looking for server-side support, IRIS SQL currently only supports the TOP clause, but we have support for LIMIT / OFFSET semantics queued for development.

Benjamin De Boe · Apr 8, 2022

Where Oracle uses the FROM DUAL pseudo-table, IRIS will just do without a FROM clause altogether for cases where you just want to select a single row of constant expressions. The following statement should work:

INSERT INTO mytable (column1, column2, column_n)
  SELECT expr1, expr2, expr_n UNION ALL
   SELECT expr1, expr2, expr_n;
Benjamin De Boe · Apr 8, 2022

As of IRIS 2021.1, we allow users to create their own aggregate functions. Perhaps there's a beautiful community contribution in there? :-)

You could build something simple where you just stuff all values in a temporary global (the name of which you pass as a state) and sort them (using $sortbegin/$sortend), maintaining a count and then in the FINALIZE method gather the actual median value.

Two caveats:

  • don't bother implementing a MERGE function. We don't support parallel execution just yet.
  • in some query execution plans, the FINALIZE method may be called more than once (e.g. if the aggregate is used in the SELECT list and say a HAVING clause). So you may want to cache your result somewhere (a PPG will do as this is in the last single-process mile of query processing, typically mere milliseconds apart)

We'll be removing these annoyances in a future version