Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Optimizations in Perl are rather limited. This is mostly due to the very permissive type system, and the absence of static typing. Features like <code>eval</code> etc. don't make it any easier, either.</p> <p>Perl does not optimize code like</p> <pre><code>my $foo = 1; if ($foo) { ... } </code></pre> <p>to </p> <pre><code>do { ... }; </code></pre> <p>However, one can declare compile time constants:</p> <pre><code>use constant FOO =&gt; 1; if (FOO) { ... } </code></pre> <p>which is then optimized (constant folding). Constants are implemented as special subroutines, with the assumption that subs won't be redefined. Literals will be folded as well, so <code>print 1 + 2 + 3</code> will actually be compiled as <code>print 6</code></p> <p>Interesting runtime optimizations include method caching, and regex optimizations. However, perl won't try to prove certain properties about your code, and will always assume that variables are truly <em>variable</em>, even if they are only ever assigned once.</p> <p>Given a Perl script, you can look at the way it was parsed and compiled by passing perl the <code>-MO=Deparse</code> option. This turns the compiled opcodes back to Perl code. The output isn't always runnable. When <code>'???'</code> turns up, this indicates code that was optimized away, but is irrelevant. Examples:</p> <pre><code>$ perl -MO=Deparse -e' "constant" ' # literal in void context '???'; $ perl -MO=Deparse -e' print 1 + 2 + 3 ' # constant folding print 6; $ perl -MO=Deparse -e' print 1 ? "yep" : "nope" ' # constant folding removes branches print 'yep'; </code></pre>
    singulars
    1. This table or related slice is empty.
    1. PODoes Perl optimize based on specific arguments, while parsing the source code?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USamon
    1. USamon
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COActually, `if( FOO ){` would become `if( 1 ){`. That is the limit of the optimization.
      singulars
      1. PO
      1. USshawnhcorey
    2. CO@shawnhcorey no, it actually compiles down to single, unconditional block, just try it out with `-MO=Deparse`. This is different from, but equivalent to an `if (1)`.
      singulars
      1. PO
      1. USamon
    3. COUnfortunately I cannot vote-up, thank you for the reply.
      singulars
      1. PO
      1. USuser2405602
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload