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Start operator ignored if limit is not set

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I'm working on a news feed that will show the most recent news in a full teaser grid, and all older news as a simpler archive-type list view. My selectors so far:

$news_full = $page->children("template=news, limit={$page->feed_count_full}");
$news_archive = $page->children("template=news, start={$page->feed_count_full}, limit=9999");

The $page->feed_count_full field controls how many items to show in the teaser grid (I've confirmed it contains the correct value, and the $news_full selector works as intended).

This works, but I don't like the limit in the second selector. Unfortunately, if I leave it out (i.e. I only specify a start, not a limit), the start is ignored and I get all news instead. Not a big problem as we will never have more than 9999 news, but it still bothers me, as semantically speaking I don't want to set a limit in this case.

Is this the intended behaviour of start/limit selectors? Is there a cleaner way to specify an offset (start selector) without a limit?

ProcessWire Version 3.0.123

Thanks!

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That's currently the way it is implemented. If there's no limit given, then PW ignores the offset (for the curios, it's implemented in PageFinder::getQueryStartLimit). It makes sense from a database point of view since MySQL's LIMIT keyword always needs a row count.

So your approach is the correct one. You could perhaps use a reasonably high number (like MySQL's maximum unsigned integer, 18446744073709551615) for your limit. If you don't want to have to remember the value, just put it intosite/config.php like "$config->maxDbLimit = 18446744073709551615;" and then use "limit={$config->maxDbLimit}" in your selector.

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Wouldn't it be better to do something like:

$news_full = $page->children("template=news, limit={$page->feed_count_full}");
$news_archive = $page->children("template=news, limit=50")->filter("id!=$news_full");

so you can keep a reasonable limit to the archive query, 50 for instance, instead of loading all the children at once?

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2 hours ago, Sergio said:

Wouldn't it be better to do something like:


$news_full = $page->children("template=news, limit={$page->feed_count_full}");
$news_archive = $page->children("template=news, limit=50")->filter("id!=$news_full");

You would need to exclude by ID withing the children selector or else the first page of $news_archive would be an unequal quantity (or empty depending on the value of feed_count_full) because pages would be filtered out after they are found.

$news_archive = $page->children("template=news, id!=$news_full, limit=50");

 

If all of the results are appearing on the same page (no pagination is used) then you can achieve it without needing a second DB query...

$news = $page->children("template=news");
$news_full = $news->slice(0, $page->feed_count_full);
$news_archive = $news->slice($page->feed_count_full);

 

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15 hours ago, BitPoet said:

That's currently the way it is implemented. If there's no limit given, then PW ignores the offset (for the curios, it's implemented in PageFinder::getQueryStartLimit). It makes sense from a database point of view since MySQL's LIMIT keyword always needs a row count.

So your approach is the correct one. You could perhaps use a reasonably high number (like MySQL's maximum unsigned integer, 18446744073709551615) for your limit. If you don't want to have to remember the value, just put it intosite/config.php like "$config->maxDbLimit = 18446744073709551615;" and then use "limit={$config->maxDbLimit}" in your selector.

Thanks, that's what I assumed. Though it would be cool if ProcessWire did this under the hood, since having a start/offset but no limit is a realistic scenario / requirement in this case for example.

12 hours ago, Robin S said:

If all of the results are appearing on the same page (no pagination is used) then you can achieve it without needing a second DB query...


$news = $page->children("template=news");
$news_full = $news->slice(0, $page->feed_count_full);
$news_archive = $news->slice($page->feed_count_full);

 

Thanks, that's exactly what I was looking for! For some reason I thought I needed two different queries since I need different fields from the two sections ^^ I need to look into the WireArray methods again, some really useful stuff there ... 🙂

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