Limits of the Firebird Database

The significant restrictions are:

• Max indexes per table is 255 in Firebird 1.5x and 64 in Firebird 1.0x.

• Max size of an index key is 254 bytes and less for compound keys in Firebird V1.x. Firebird 2 and future versions allow keys up to 25% of the size of a database pages. Character columns that sort in dictionary order rather than byte order require more than one byte per character to represent their collating sequence. As a result, the effective limit on key size may be as low as 90 bytes for some languages. Version 2 will lift this restriction.

• Max number of conjuncts is 255. A conjunct is a pair of conditions combined with an AND.

  WHERE F1 = 1 and F2 >= 2 and F2 = 5
  

  is 3 conjuctions, but:

  WHERE F1 = 1 or F2 >= 2 or F2 = 5
  

  is 1 conjunction

• Maximum size of a table is approximately 37Gb of compressed data, not depending on the size of the records, record count or page size. Version 2 does not have this restriction.

• Metadata names are restricted to 31 characters.

• The maximum size of a blob is 2Gb.

• Rows are restricted to 32767 bytes.

• A database can contain no more than 32767 tables.

• The maximum size for a database is over 30 terabytes.

• Maximum number of elements in an IN list is 1499.

  select name from phones where extension
      in (0000, 0001, 0002 ... 1499);