Create Table If Not Exists Hanging

Question

I am still new to using databases, but currently I am using a mysql database and attempting to make my bash script unbreakable because it might be used in several different environments (dev, qa, etc). I know it will run correctly without this one line.

CREATE TABLE IF NOT EXISTS backupfiles (fileName VARCHAR(20), archiveId VARCHAR(500), checkSum VARCHAR(100), glacierVault VARCHAR(100), timeStamp date);

I also know that if I put that exact line into my database when that table does not exist then it runs perfectly and if it does exist already it gives me a warning, but does not break.

+-------+------+------------------------------------+
| Level | Code | Message                            |
+-------+------+------------------------------------+
| Note  | 1050 | Table 'backupfiles' already exists |
+-------+------+------------------------------------+

When I run the line above and there is no table named backupfiles it works perfectly, but when there is it hangs(when I say hangs it sits there and does nothing) 95% of the time and 5% of the time works. Has anyone run into a problem like this? I am using AWS RDS(Amazon Web serices Relational Database Service) and the mysql server is 5.5.27

Here is all of my code that I relates to the mysql database

mysql -h portal-rds -u $user --password=$mysqlpw <<QUERY_INPUT
CREATE DATABASE IF NOT EXISTS $DATABASE;
use $DATABASE;
CREATE TABLE IF NOT EXISTS backupfiles (fileName VARCHAR(20), archiveId VARCHAR(500), checkSum VARCHAR(100), glacierVault VARCHAR(100), timeStamp date);
INSERT INTO backupfiles VALUES ('$archive_file_name', '$archiveID', '$CURRENTVAULT', '$checkSum', CURDATE());
COMMIT;
QUERY_INPUT

Answer 1

I find this troubling for two reasons

REASON #1

This could be a bug that never got squashed out of MySQL 5.5.17

• Nov 08, 2011 : http://bugs.mysql.com/bug.php?id=63144 (Status is Needs Triage on MySQL 5.5.17)
• Mar 21, 2011 : http://bugs.mysql.com/bug.php?id=60563 (MySQL 5.5.10)
• Jun 23, 2006 : http://bugs.mysql.com/bug.php?id=20662

REASON #2

You are trying to acquire a metadata lock on an InnoDB table in an RDS environment? Ouch !!!

Possible Workaround

Instead of trusting the metadata locking in RDS, ask the information_schema if the table exists already. Suppose the table is mydb.backupfiles. Run this query:

SELECT COUNT(1) FROM information_schema.tables
WHERE table_schema='mydb' AND table_name='backupfiles';

If the answer comes back 0, run CREATE TABLE backupfiles .... Otherwise, don't run it.

Possible Solution

Upgrade to the Latest MySQL (5.6.12) or the Latest MySQL5.5 (5.5.31). Hopefully, this issue was solved in a more recent version

Give it a Try !!!

UPDATE 2013-07-11 15:16 EDT

Here is a rewrite of your bash code to check if the table already exists

    echo "CREATE DATABASE IF NOT EXISTS $DATABASE;" > /tmp/runthis.sql
    echo "use $DATABASE;" >> /tmp/runthis.sql
    SQLSTMT="SELECT COUNT(1) FROM information_schema.tables"
    SQLSTMT="${SQLSTMT} WHERE table_schema='${DATABASE}' AND table_name='backupfiles';"
    TABLE_EXISTS=`mysql -h portal-rds -u $user --password=$mysqlpw -ANe"${SQLSTMT}"`
    if [[ ${TABLE_EXISTS} -eq 0 ]]; then
      SQLSTMT="CREATE TABLE backupfiles (fileName VARCHAR(20),"
      SQLSTMT="${SQLSTMT} archiveId VARCHAR(500), checkSum VARCHAR(100),"
      SQLSTMT="${SQLSTMT} glacierVault VARCHAR(100), timeStamp date);"
      echo "${SQLSTMT}" >> /tmp/runthis.sql
    fi
    SQLSTMT="INSERT INTO backupfiles VALUES ('$archive_file_name',"
    SQLSTMT="${SQLSTMT} '$archiveID', '$CURRENTVAULT', '$checkSum', CURDATE());"
    echo "${SQLSTMT}" >> /tmp/runthis.sql
    echo "COMMIT;" >> /tmp/runthis.sql
    mysql -h portal-rds -u $user --password=$mysqlpw < /tmp/runthis.sql