7.6. Restrictions

7.6.1. LMS project related

Amount of money (in 'cash' table) was stored (as of lms-1.1) as 32 integer value, so if you had 5000 users you might had problems in 8 years or so. Nowadays (since lms-1.1.7 Hathor) we use more appropriate type [ decimal (9.2), with 2 significant places after dot and 9 numers for whole sum] and the maximum is 9'999'999.99 (sum of all in/out cash operations). Procedures converting numbers to words are able to process numbers as big as 10^18.

7.6.2. SQL engine related

• MySQL

  • Database size:

    Following MySQL documentation ("How Big Can MySQL Tables Be?" in chapter "Table size"), MySQL 3.22 is restricted 4GB per table. Since 3.23 restriction is 8 million terabytes (2^63 bytes). It's worth to mention, however, that some systems have filesystem level, usually at 2 or 4 GB.

  • Number of records:

    True information can be obtained, by issuing (in mysql shell):

    mysql> show table status;
    
    ...| Avg_row_length | Data_length | Max_data_length | Index_length |
    ...|             44 |       24136 |      4294967295 |        19456 |

    See that free space is about 175 000 time more than currently used, so until you plan to have 100000 users, you're pretty safe in this matter :-)

• PostgreSQL

  • Database size:

    PostgreSQL stores data in 8kB blocks. Number of blocks in bound to 32-bit number with sign, which gives maximum table size of 16 terabytes. Filesystem restrictions are avoided by keeping data in slices, 1GB each.

  • Number of records:

    PostgreSQL does not have row number limit for tables.