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According to the PHP documentation, mysql_insert_id takes the last inserted id from the mysql table.

My question is, if I have a website that inserts more than 2 rows per second to the DB, can I use the mysql_insert_id and get the correct ID I am referring to in the INSERT query a line before?



From the MySQL manual:

The ID that was generated is maintained in the server on a per-connection basis. This means that the value returned by the function to a given client is the first AUTO_INCREMENT value generated for most recent statement affecting an AUTO_INCREMENT column by that client. This value cannot be affected by other clients, even if they generate AUTO_INCREMENT values of their own. This behavior ensures that each client can retrieve its own ID without concern for the activity of other clients, and without the need for locks or transactions.

Short version: it is safe to use.

Friday, October 7, 2022

I would say just build it yourself. You can set it up like this:

$query = "INSERT INTO x (a,b,c) VALUES ";
foreach ($arr as $item) {
  $query .= "('".$item[0]."','".$item[1]."','".$item[2]."'),";
$query = rtrim($query,",");//remove the extra comma
//execute query

Don't forget to escape quotes if it's necessary.

Also, be careful that there's not too much data being sent at once. You may have to execute it in chunks instead of all at once.

Saturday, November 5, 2022

The function you're looking for is find_in_set:

 select * from ... where find_in_set($word, pets)

for multi-word queries you'll need to test each word and AND (or OR) the tests:

  where find_in_set($word1, pets) AND find_in_set($word2, pets) etc 
Wednesday, August 17, 2022

BinaryReader does use a buffer but only to read enough bytes from the base stream to convert a value. In other words, ReadInt32() will buffer 4 bytes first, ReadDecimal() will buffer 16 bytes first, etcetera. ReadString() is the trickier method but it has counter-measures as well, a string is encoded in the file by BinaryWriter which writes the string length first. So that BinaryReader knows exactly how many bytes to buffer before converting the string.

So the buffer is always empty after one of the ReadXxx() method returns and calling Seek() on the BaseStream is fine. Also the reason that Microsoft didn't need to override the Seek() method.

The cautionary note in the MSDN article is appropriate, you certainly will read that "offset" value more than once if you call a ReadXxx() method after the Seek() call. I however assume that was entirely intentional.

Friday, September 2, 2022

I think you can run your program with LD_DEBUG set to see the exact order:

LD_DEBUG=all <myprogram>

EDIT: If you look at the source code of the runtime linker (glibc 2.7), specifically in files:

  • sysdeps/unix/sysv/linux/init-first.c
  • sysdeps/i386/init-first.c
  • csu/libc-start.c
  • sysdeps/i386/elf/start.S

you will see that argc, argv and environ (alias for __environ) are set before any global constructors are called (the init functions). You can follow the execution starting right from _start, the actual entry point (start.S). As you've quoted Stevens "An array of strings called the enviroment is made available when the process begins", suggesting that environment assignment happens at the very beginning of the process initialization. This backed by the linker code, which does the same, should give you sufficient peace of mind :-)

EDIT 2: Also worth mentioning is that environ is set early enough that even the runtime linker can query it to determine whether or not to output verbosely (LD_DEBUG).

Friday, September 30, 2022
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