added pg functions keyword and identifier, updated README

[fritzy]

Not sure if you want the PG statements set in there, or how you wanted to deal with different dialects, but this is one way to do it. I wanted to be able to enforce some user input filtering on identifiers and keywords.

[fritzy]

@nlf fixed that and replaced function in the examples (were erroneously keyword when they should have been identifier)

[felixfbecker]

Thanks for the PR, I don't know how I should feel about it though. The purpose of this module was to take a template string and transform it into an object with placeholder queries and values that both pg and mysql understand, and let them do the escaping. You can use SQL.raw() when the input can be trusted or use the database driver escaping functions (that's why I added an example in readme with mysql.escapeId()). pg provides something similar: brianc/node-postgres#396 (maybe I should add an example with these too). Adding specific pq functions kind of breaks with the dual-compatibility. I guess it is also generally better to validate stricter - i.e. if you insert a sort direction, check for asc or desc.
Do you have a specific use case?

[fritzy]

Ah, I didn't realize the pg client had these already; these seem to be undocumented features.

I have to say that I don't like that it's bothering to produce 2 strings when all I need is one, but otherwise this little module is great.

[felixfbecker]

Yeah, I only found them by searching in the repo. Maybe someone should open a PR to add this to their docs?
And what do you think about adding an option to explicitly set the driver?

[fritzy]

Yup, that's why I opened issue #3

[fritzy]

@felixfbecker I was trying to avoid this:

SQL`... ORDER BY ${SQL.raw(pg.Client.prototype.escapeIdentifier(args.orderBy))} ${SQL.raw(validSort.has(args.sort.toUpperCase()) ? args.sort : 'DESC')}`

[nlf]

what if we just allow passing a second parameter to SQL.raw that can be an optional escaping function? then it would be more like

let escape = pg.Client.prototype.escapeIdentifier;
let query = SQL`... ORDER BY ${SQL.raw(args.orderBy, escape)}`

[nlf]

though i'm not sure that's really much better than just doing

let escape = pg.Client.prototype.escapeIdentifier;
let query = SQL`... ORDER BY ${SQL.raw(escape(args.orderBy))}`

maybe just a little easier to read since it has fewer parens

[felixfbecker]

Yeah, it's unfortunate that the escape functions sits on the client prototype. I would suggest doing

let escape = pg.Client.prototype.escapeIdentifier