greenrobot/greenDAO · error · DaoException

( ) does not have a single-column primary key

Error message

${this} (${config.tablename}) does not have a single-column primary key

What it means

Several greenDAO operations (deleteAll, count-by-key helpers, key-array based queries) only support entities with exactly one primary-key column. assertSinglePk() throws DaoException when config.pkColumns.length != 1 (zero or composite keys).

Solutions

1. Give the entity a single-column primary key (annotate one field with @Id) and regenerate DAOs.
2. Avoid single-PK-only APIs on composite-key entities; use queryBuilder/deleteInTx instead.
3. For no-PK entities, add an autoincrement id column via migration.
4. Wrap the call in a check of config.pkColumns length in custom DAO code.

Example fix

// before (composite key entity)
dao.deleteAll(); // throws
// after
List<Thing> all = dao.queryBuilder().build().list();
dao.deleteInTx(all); // works with composite keys

if (config.pkColumns.length != 1) {
    // use queryBuilder/deleteInTx path instead of single-PK APIs
}

try {
    dao.count();
} catch (DaoException e) {
    if (e.getMessage().contains("single-column primary key")) {
        long n = dao.queryBuilder().buildCount().count(); // PK-agnostic fallback
    } else throw e;
}

When it happens

Trigger: Calling count(), deleteAll(), or key-based helpers on a DAO whose entity uses a composite primary key or has no primary key at all (allColumns != pkColumns).

Common situations: Generated entity with @Id plus an additional @Unique composite expectation; legacy tables with composite PKs; entities where no @Id was declared so pkColumns is empty.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Expected unique result, but count was
• Cannot delete entity, key is null
• Entity does not exist in the database anymore
• Cannot update entity without key - was it inserted before?
• Entity may not be null

AI-assisted analysis of greenrobot/greenDAO@0bbb338e17 (2026-09-08). Data as JSON: /api/errors/f564a16702c68e72. Report an issue: GitHub.

Appendix: source

Thrown at DaoCore/src/main/java/org/greenrobot/greendao/AbstractDao.java:917

            }
        }
        if (txEx != null) {
            throw txEx;
        }
    }

    /**
     * Updates the given entities in the database using a transaction.
     *
     * @param entities The entities to update.
     */
    public void updateInTx(T... entities) {
        updateInTx(Arrays.asList(entities));
    }

    protected void assertSinglePk() {
        if (config.pkColumns.length != 1) {
            throw new DaoException(this + " (" + config.tablename + ") does not have a single-column primary key");
        }
    }

    public long count() {
        return statements.getCountStatement().simpleQueryForLong();
    }

    /** See {@link #getKey(Object)}, but guarantees that the returned key is never null (throws if null). */
    protected K getKeyVerified(T entity) {
        K key = getKey(entity);
        if (key == null) {
            if (entity == null) {
                throw new NullPointerException("Entity may not be null");
            } else {
                throw new DaoException("Entity has no key");
            }
        } else {
            return key;

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