1
Diagnostic step 1
Before running migrations, plan to drain or recycle connection pools (perform a controlled rolling restart of application instances) so sessions do not hold stale prepared statements.
FULL AI ANALYSIS
JDBC clients fail with 'bind message supplies 0 parameters' after ALTER COLUMN type; prepared statements misbehave on PostgreSQL 14
Generated Oct 3, 2026, 12:35:03 AM
Analysis summary
The PostgreSQL server and JDBC driver interaction with prepared statements can cause type OID mismatches when the server schema changes. The JDBC driver may cache parameter type OIDs or the server may retain server‑side prepared plans that expect the old type, causing bind errors once the column type changes. Because client sessions maintain their prepared state, new schema cannot be automatically reconciled for existing prepared statements. The observed behavior (works on new connections, fails on existing pooled connections) strongly indicates cached prepared statements are the culprit.
Possible causes
Server‑side prepared statements or cached plans referencing old type OIDs after ALTER TABLE ALTER COLUMN type
95%Connection pool retaining sessions with prepared statements that are invalid after schema change
95%JDBC driver performing automatic server‑side prepare and caching parameter metadata in the client across connection reuse
80%Suggested fixes
2
Diagnostic step 2
As a hotfix without restarting the app: execute DEALLOCATE ALL or DISCARD ALL in affected sessions to clear server‑side prepared statements. If you cannot run commands in each session, fully recycle the pool as soon as feasible.
3
Diagnostic step 3
Configure the JDBC driver to avoid automatic server‑side prepares (set prepareThreshold to 0 for the PostgreSQL JDBC driver) during deployments that alter parameter types; test this in staging first.
4
Diagnostic step 4
Collect diagnostics for escalation: pg_prepared_statements view output, server logs around the migration, JDBC driver and pool configuration (prepareThreshold, useServerPrepStmts), and a sample stack trace of the error from the application. Share these with the DBA and application engineering teams when requesting a coordinated migration plan.
5
Diagnostic step 5
For long term: adopt safe migration patterns (create new column, backfill, swap, and DROP old column during low traffic or with pool recycle) to avoid in‑place type changes that break prepared statements.