EC
1076
MySQLERRORCommonDDLHIGH confidence

Too many keys specified; max 64 keys allowed

Production Risk

Low — DDL fails; no data loss.

What this means

ER_TOO_MANY_KEYS (1076, SQLSTATE 42000) is raised when a CREATE TABLE or ALTER TABLE statement defines more than 64 indexes on a single table.

Why it happens
  1. 1Auto-generated schema (ORM or migration tool) creates an index for every column
  2. 2Manual over-indexing for query optimization without consolidating composite indexes
How to reproduce
trigger — this will error
trigger — this will error
-- CREATE TABLE with 65+ INDEX definitions

expected output

ERROR 1076 (42000): Too many keys specified; max 64 keys allowed

Fix

Consolidate single-column indexes into composite indexes

WHEN Multiple single-column indexes exist on frequently-joined columns.

Consolidate single-column indexes into composite indexes
-- Instead of INDEX(a), INDEX(b), INDEX(c):
ALTER TABLE t ADD INDEX idx_abc (a, b, c);
ALTER TABLE t DROP INDEX idx_a, DROP INDEX idx_b, DROP INDEX idx_c;

Why this works

A composite index (a, b, c) can satisfy queries filtering on a, (a,b), or (a,b,c), replacing three separate indexes.

What not to do

✕ Index every column individually

Over-indexing slows down writes and increases storage; composite indexes cover multiple query patterns more efficiently.

Sources
Official documentation ↗

MySQL 8.0 — 1076 ER_TOO_MANY_KEYS

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