MySQL Proxy SQL Routing Failed
MySQL ProxySQL routes queries to wrong host when query rules are misconfigured.
Category archive
Database fixes
Published troubleshooting guides for database issues.
PostgreSQL PgBouncer Connection Pool Exhausted
PostgreSQL PgBouncer cannot allocate server connections when pool_size is too small.
MySQL Performance Schema Overhead High
MySQL Performance Schema causes overhead when too many instruments are enabled.
PostgreSQL Statistics Collector Not Running
PostgreSQL statistics collector is not running when track_activities or track_counts is disabled.
MySQL Query Cache Fragmentation High
MySQL query cache fragmentation reduces hit rate when many small queries cause fragmentation.
PostgreSQL Plan Cache Stale
PostgreSQL uses suboptimal cached plan when table statistics have changed significantly.
MySQL Prepared Statement Cache Full
MySQL cannot prepare new statements when prepared statement cache limit is reached.
PostgreSQL Cursor Without Scroll Error
PostgreSQL cursor cannot scroll backward when declared without SCROLL option.
MySQL View WITH CHECK OPTION Violated
MySQL rejects insert or update on view when data would not be visible through the view.
PostgreSQL Materialized View Stale
PostgreSQL materialized view returns outdated data when REFRESH has not been scheduled.
MySQL Generated Column Update Failed
MySQL cannot update generated column when expression references non-deterministic function.
PostgreSQL Array Operation Slow
PostgreSQL array containment queries are slow when GIN index on array column is missing.
MySQL Spatial Index Not Used
MySQL spatial index is ignored when query uses unsupported functions or data types.
PostgreSQL PostGIS Query Performance Degraded
PostgreSQL PostGIS spatial queries are slow when GiST index is not used or statistics are stale.
MySQL JSON Column Query Slow
MySQL JSON extraction queries are slow when virtual columns or indexes are not defined.
PostgreSQL Full Text Search Not Working
PostgreSQL full text search returns no results when GIN index is not built or text search config is wrong.
MySQL SQL Mode Strict Violation
MySQL rejects invalid data values when STRICT_TRANS_TABLES or STRICT_ALL_TABLES is enabled.
PostgreSQL Row Level Security Bypass
PostgreSQL RLS policies are bypassed when superuser or table owner accesses data.
MySQL Charset Collation Conflict
MySQL query fails when comparing columns with different character sets or collations.
PostgreSQL Character Encoding Mismatch
PostgreSQL character conversion fails when client encoding differs from database encoding.
MySQL Auto Increment No More Values
MySQL auto-increment column reaches maximum value and cannot generate new IDs.
PostgreSQL Sequence Out of Sync
PostgreSQL sequence generates duplicate values when not synchronized with table data.
MySQL Partition Pruning Not Working
MySQL query scans all partitions when partition pruning conditions are not satisfied.
PostgreSQL TOAST Table Corruption
PostgreSQL TOAST table storing large values becomes corrupted after hardware failure.
MySQL InnoDB Log File Size Mismatch
MySQL InnoDB refuses to start when ib_logfile size does not match configuration.
PostgreSQL Checkpoint Taking Too Long
PostgreSQL checkpoints take too long when checkpoint_timeout or checkpoint_completion_target is misconfigured.
MySQL Fragmentation High Impact on Performance
MySQL table fragmentation degrades performance when OPTIMIZE TABLE has not been run.
PostgreSQL Table Bloat Excessive
PostgreSQL table has excessive bloat when VACUUM cannot keep pace with UPDATE/DELETE operations.
MySQL Router Connection Failed
MySQL Router cannot route connections when InnoDB Cluster topology is unavailable.
PostgreSQL pgLogical Replication Error
PostgreSQL pgLogical replication fails when origin or target database is unreachable.
MySQL Group Replication Member Offline
MySQL group replication member is excluded due to network partition or certification failure.
PostgreSQL Logical Decoding Slot Inactive
PostgreSQL logical replication slot becomes inactive when consumer disconnects or WAL is removed.
MySQL Federated Table Connection Lost
MySQL federated table cannot connect to remote server due to network or authentication issues.
PostgreSQL Foreign Data Wrapper Error
PostgreSQL FDW query fails when remote server is unreachable or credentials are invalid.
MySQL SSL Handshake Error
MySQL SSL handshake fails when certificates are expired or cipher suites do not match.
PostgreSQL SSL Connection Failed
PostgreSQL SSL connection fails due to certificate verification or protocol mismatch.
MySQL InnoDB Corrupted Table
MySQL InnoDB table is corrupted after crash or storage failure requiring recovery.
PostgreSQL Transaction ID Wraparound
PostgreSQL approaches transaction ID wraparound when vacuum has not run for extended period.
MySQL Slow Query Not Using Index
MySQL slow query performs full table scan when index cannot be used for the query pattern.
PostgreSQL Index Not Being Used
PostgreSQL query planner chooses sequential scan over index due to stale statistics or cost estimates.
MySQL InnoDB Buffer Pool Hit Rate Low
MySQL InnoDB buffer pool hit rate drops when pool size is too small for working dataset.
PostgreSQL Autovacuum Not Running
PostgreSQL autovacuum fails to run due to configuration issues or long-running transactions.
MySQL Binlog Disk Space Exhausted
MySQL binary logs consume all disk space when purge is disabled or replication is lagging.
PostgreSQL WAL Disk Full
PostgreSQL WAL segments consume all disk space when archiving fails or replication is stuck.
MySQL Replication Slave Stopped
MySQL slave replication stops due to duplicate key errors or relay log corruption.
PostgreSQL Replication Lag Critical
PostgreSQL standby replica falls behind primary due to write throughput or network latency.
MySQL Deadlock Found When Transaction
MySQL detects deadlock when two transactions wait for locks held by each other.
PostgreSQL Lock Wait Timeout
PostgreSQL queries timeout waiting for locks when transactions hold conflicting locks.
MySQL Too Many Connections Error
MySQL server returns too many connections error when connection limit is reached.
PostgreSQL Connection Limit Exceeded
PostgreSQL rejects new connections when max_connections is reached or connection pool is exhausted.