How to fix cannot refresh materialized view concurrently in PostgreSQL

Query the PostgreSQL system catalog to list all indexes on your materialized view:

-- Replace 'my_materialized_view' with your actual view name
SELECT indexname, indexdef
FROM pg_indexes
WHERE tablename = 'my_materialized_view'
  AND schemaname = 'public';

Look for an index that is marked as unique. If no index appears, or if the only index is not unique, you need to create one.

Create a unique index with NO WHERE clause on one or more columns of the materialized view. Choose columns that have unique or near-unique values:

-- Example: if the materialized view has an id column
CREATE UNIQUE INDEX idx_my_mv_unique ON my_materialized_view(id);

-- Or use multiple columns if needed
CREATE UNIQUE INDEX idx_my_mv_unique ON my_materialized_view(schema_id, object_id);

The index MUST:
- Be declared UNIQUE
- Contain no WHERE clause (no partial indexes)
- Not be built on expressions like LOWER(name) or id + 1
- Only include plain column references

Confirm the index you created is truly unconditional:

SELECT indexdef
FROM pg_indexes
WHERE tablename = 'my_materialized_view'
  AND schemaname = 'public'
  AND indexname = 'idx_my_mv_unique';

The indexdef should output something like:

CREATE UNIQUE INDEX idx_my_mv_unique ON public.my_materialized_view(id)

If it contains a WHERE clause or function calls, drop it and recreate it without those restrictions.

Now that a valid unique index exists, the concurrent refresh should succeed:

REFRESH MATERIALIZED VIEW CONCURRENTLY my_materialized_view;

If you still encounter an error, check that:
- The view definition hasn't changed
- The index still exists and is marked UNIQUE
- You are not combining CONCURRENTLY with WITH NO DATA (use one or the other)
- Your PostgreSQL version is 9.4 or later (when CONCURRENTLY was introduced)

Concurrent refresh is more resource-intensive than a standard refresh because it:
- Creates a temporary table with the new materialized data
- Performs a full outer join to detect changes
- Avoids locks that would block read queries

If your materialized view is small or updates are infrequent, a non-concurrent refresh may be faster:

-- Standard refresh (locks the view, but faster for small views)
REFRESH MATERIALIZED VIEW my_materialized_view;

-- Concurrent refresh (slower, keeps view readable)
REFRESH MATERIALIZED VIEW CONCURRENTLY my_materialized_view;

Choose based on your availability requirements and view size.