Method buildCheckQuery

/**
 * Checks a DDL query to see if it is a known type
 * If yes, build a check query to see if the DDL has been run on the database.
 * If successful, the $msgElements, $queryType, $checkStatus and $checkQuery fields are populated.
 * The $msgElements contains the text to create the user message.
 * The $checkQuery contains the SQL query to check whether the schema change has
 * been run against the current database. The $queryType contains the type of
 * DDL query that was run (for example, CREATE_TABLE, ADD_COLUMN, CHANGE_COLUMN_TYPE, ADD_INDEX).
 * The $checkStatus field is set to zero if the query is created
 *
 * If not successful, $checkQuery is empty and , and $checkStatus is -1.
 * For example, this will happen if the current line is a non-DDL statement.
 *
 * @return void
 *
 * @since  2.5
 */
protected function buildCheckQuery()
{
    // Initialize fields in case we can't create a check query
    // Change status to skipped
    $this->checkStatus = -1;
    $result = null;
    // Remove any newlines
    $this->updateQuery = str_replace("\n", '', $this->updateQuery);
    // Fix up extra spaces around () and in general
    $find = array('#((\\s*)\\(\\s*([^)\\s]+)\\s*)(\\))#', '#(\\s)(\\s*)#');
    $replace = array('($3)', '$1');
    $updateQuery = preg_replace($find, $replace, $this->updateQuery);
    $wordArray = explode(' ', $updateQuery);
    // First, make sure we have an array of at least 6 elements
    // if not, we can't make a check query for this one
    if (\count($wordArray) < 6) {
        // Done with method
        return;
    }
    // We can only make check queries for alter table and create table queries
    $command = strtoupper($wordArray[0] . ' ' . $wordArray[1]);
    if ($command === 'ALTER TABLE') {
        $alterCommand = strtoupper($wordArray[3] . ' ' . $wordArray[4]);
        if ($alterCommand === 'ADD') {
            $result = 'SELECT * FROM INFORMATION_SCHEMA.Columns ' . $wordArray[2] . ' WHERE COLUMN_NAME = ' . $this->fixQuote($wordArray[5]);
            $this->queryType = 'ADD';
            $this->msgElements = array($this->fixQuote($wordArray[2]), $this->fixQuote($wordArray[5]));
        } elseif ($alterCommand === 'CREATE INDEX') {
            $index = $this->fixQuote(substr($wordArray[5], 0, strpos($wordArray[5], '(')));
            $result = 'SELECT * FROM SYS.INDEXES ' . $wordArray[2] . ' WHERE name = ' . $index;
            $this->queryType = 'CREATE INDEX';
            $this->msgElements = array($this->fixQuote($wordArray[2]), $index);
        } elseif (strtoupper($wordArray[3]) === 'MODIFY' || strtoupper($wordArray[3]) === 'CHANGE') {
            $result = 'SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS  WHERE table_name = ' . $this->fixQuote($wordArray[2]);
            $this->queryType = 'ALTER COLUMN COLUMN_NAME =' . $this->fixQuote($wordArray[4]);
            $this->msgElements = array($this->fixQuote($wordArray[2]), $this->fixQuote($wordArray[4]));
        }
    }
    if ($command === 'CREATE TABLE') {
        $table = $wordArray[2];
        $result = 'SELECT * FROM sys.TABLES WHERE NAME = ' . $this->fixQuote($table);
        $this->queryType = 'CREATE_TABLE';
        $this->msgElements = array($this->fixQuote($table));
    }
    // Set fields based on results
    if ($this->checkQuery = $result) {
        // Unchecked status
        $this->checkStatus = 0;
    } else {
        // Skipped
        $this->checkStatus = -1;
    }
}