crud-queue-optimization.php

<?php
$ops = array(
  array('operation' => 'insert'),
  array('operation' => 'update'),
  array('operation' => 'update'),
  array('operation' => 'update'),
);

$ops2 = array(
  array('operation' => 'update'),
  array('operation' => 'update'),
  array('operation' => 'delete'),
);

var_dump(_conglomerateclient_compress_node_ops($ops));
var_dump(_conglomerateclient_compress_node_ops($ops2));

/**
 * The task of this function is to remove unnecessary operations. Multiple
 * consequetive updates can be reduced to just the last update. Updates
 * preceding a delete can be skipped altogether.
 *
 * @param array $ops
 * @return array
 */
function _conglomerateclient_compress_node_ops($ops) {
  $last_op = FALSE;
  for ($i=0; $i<count($ops); $i++) {
    if ($ops[$i]['operation'] == 'delete' || $ops[$i]['operation'] == 'update') {
      if ($last_op == 'update') {
        $ops[$i-1] = NULL;
      }
    }
    $last_op = $ops[$i]['operation'];
  }
  return $ops;
}

output.txt

array(4) {
  [0]=>
  array(1) {
    ["operation"]=>
    string(6) "insert"
  }
  [1]=>
  NULL
  [2]=>
  NULL
  [3]=>
  array(1) {
    ["operation"]=>
    string(6) "update"
  }
}
array(3) {
  [0]=>
  NULL
  [1]=>
  NULL
  [2]=>
  array(1) {
    ["operation"]=>
    string(6) "delete"
  }
}