Character Index Limits

The maximum indexed string length is 9 bytes less than the maximum key length.The maximum indexable string length depends on the page size, the character set, and the collation.

Table 1. Maximum indexable (VAR)CHAR length
Page Size	Maximum Indexable String Length by Charset Type
Page Size	1 byte/char	2 byte/char	3 byte/char	4 byte/char
4096	1015	507	338	253
8192	2039	1019	679	509
16384	4087	2043	1362	1021
32768	8183	4091	2727	2045

Note	Depending on the collation, the maximum size can be further reduced as case-insensitive and accent-insensitive collations require more bytes per character in an index.See also Character Indexes in Chapter Data Types and Subtypes.

Parallelized Index Creation

Since Firebird 5.0, index creation can be parallelized.Parallelization happens automatically if the current connection has two or more parallel workers — configured through ParallelWorkers in firebird.conf or isc_dpb_parallel_workers — and the server has parallel workers available.