mORMot Open Source

FLIXNRK

Member

Registered: Yesterday

Posts: 1

FormatUTF8 / ToArrayOfConst – Is there a limit on the number of params

Hi everyone,

I’m using mORMot 2 and I’ve run into a strange limit with FormatUTF8.
I build an SQL string template like this (with many % placeholders) and then call:
sql := FormatUTF8(jsonTemplate, TDocVariantData(bounds).ToArrayOfConst);

As soon as I use more than ~30 placeholders/arguments, I start getting errors like “too many arguments” or the formatting simply fails.
If I take the same template and the same arguments and run it through Delphi/FPC’s Format() instead, it works fine with more parameters.

So my question is:

Does FormatUTF8 in mORMot 2 have a built-in limit for the number of arguments, or is this a known issue/bug?
And is there a recommended way to handle cases where I need 40+ parameters (e.g. big SQL UPDATE statements)?

Thanks in advance!

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 15,276

Website

Re: FormatUTF8 / ToArrayOfConst – Is there a limit on the number of params

There is indeed a limitation of number of parameters - see TFormatUtf8 record in mormot.core.text:

blocks: array[0..63] of TTempUtf8;

But is on purpose, because it is to be build from source, so 32 parameters seems big enough in real source code.
Use a local TTextWriter instead, e.g. via TTextWriter.CreateOwnedStream(tmp).

Anyway, don't go this way. Use SQL parameters. Pre-rendering the UPDATE as SQL with inlined parameters is unsafe, subject to SQL injection. And slower, since the statement can't be prepared and reused between calls.