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Re: [NonGNU ELPA] New package: sqlite3

From: Lynn Winebarger
Subject: Re: [NonGNU ELPA] New package: sqlite3
Date: Tue, 21 Mar 2023 07:56:25 -0400

On Tue, Mar 21, 2023 at 7:08 AM Philip Kaludercic <philipk@posteo.net> wrote:
> Lynn Winebarger <owinebar@gmail.com> writes:
> > On Tue, Mar 21, 2023 at 3:22 AM Jean Louis <bugs@gnu.support> wrote:
> >> * Philip Kaludercic <philipk@posteo.net> [2023-03-14 19:17]:
> >> > Jonas Bernoulli <jonas@bernoul.li> writes:
> >> >
> >> > >> Do you have a link to the package you are talking about?
> >> > >
> >> > > Ups, here you go: https://github.com/pekingduck/emacs-sqlite3-api
> >> >
> >> > Would you happen to know if there is some rx-like, s-expression based
> >> > language for constructing SQL queries.  I am not looking for anything
> >> > generic, just a way to avoid writing long strings.
> >>
> >> While such packages exists, for me I do not find them usable as then I
> >> have to forget about the SQL and learn about the new Emacs Lisp
> >> structure that is to correspond to SQL. I see personally no benefit in
> >> that.
> >
> > There are a couple of good reasons to use an sexpr-based query language:
> > * Avoiding sql injection issues by putting all the boilerplate for
> > interpolating data into queries into a macro expander
> To be fair, this is not a concern because SQLite supports parameterised
> queries:
>   (sqlite-execute db "insert into foo values (?, ?)" '("bar" 2))

That's a pretty limited notion of interpolating data into code.  Using
metadata stored in tables and systematically generating queries from
that metadata is a pretty standard technique even among SQL
programmers that aren't otherwise inclined to writing recursive macros
to implement DSLs.

> > * Treating code as data and vice-versa is a powerful programming technique
> Not sure about this.... Strings are data too, but neither the SQL
> statements or the regular expressions are (Elisp) code.

Are lisp macros written in terms of string interpolation?  If there
are no other types of data than strings, fine, but that's not really
the case - machine instructions have different operations for
integers/floats/pointers, a good programming abstraction will reflect
that.  If the underlying machine used strings to represent numbers and
arithmetic operations took two numeric strings and produced another
numeric string, maybe there'd be a case to be made (although the first
point above still mitigates against it).

> To me the
> advantage of something like `rx' is that I can insert comments and make
> use of regular indentation.  Then again, it would also be possible to
> provide specialised SQLite wrappers (sqlite-insert, sqlite-update, ...)
> instead of taking a `rx' like approach to generating strings.
> > The real power of embedding sqlite in elisp will come when sqlite data
> > structures can be used as efficient representations of sets and
> > relations in lisp code.  Eventually, I would also expect to see
> > mutually recursive code enabled, with "virtual table" modules for
> > emacs data structures so they can be transparently used in sql code,
> > along with sql functions written in lisp.  For example, you might
> > create a table from lisp data using a select statement rather than
> > executing a large number of insert statements.  In-memory databases
> > would not be unusual, and should be dumpable objects.
> What is the point of using a in-memory database if you want to dump it?

It's just another data structure at that point, so why wouldn't I want
to be able to include it in my pdmp file?  Why would I want to make my
internal data structure available as a separate file, or manage
creating and tracking those files?

Maybe having a separate primitive type for a "table" with named
columns that happens to be represented with a sqlite_statement would
make the abstraction clearer?


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