Postgres JDBC driver: PSQLException: syntax error at or near RETURNING

Question

For some reason the JDBC PostgreSQL driver is adding: RETURNING * to the end of select statements. Why?

Code:

protected static final String AUTH_QUERY = "SELECT \"SECRET\" FROM \"user\" WHERE \"NAME\" = :name";

String password = sql2o.open().createQuery(AUTH_QUERY).addParameter("name", username).executeScalar(String.class);

Exception:

org.postgresql.util.PSQLException: ERROR: syntax error at or near "RETURNING"
  Position: 47
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2161)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1890)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:255)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:559)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:417)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:302)
    at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeQuery(NewProxyPreparedStatement.java:76)
    at org.sql2o.Query.executeScalar(Query.java:533)
    at org.sql2o.Query.executeScalar(Query.java:577)
    at org.sql2o.Query.executeScalar(Query.java:568)

Data source (JNDI):

<Configure id="wac" class="org.eclipse.jetty.webapp.WebAppContext">

    <New id="mydb" class="org.eclipse.jetty.plus.jndi.Resource">
        <Arg></Arg>
        <Arg>jdbc/mydb</Arg>
        <Arg>
            <New class="com.mchange.v2.c3p0.ComboPooledDataSource">
                <Set name="driverClass">org.postgresql.Driver</Set>
                <Set name="jdbcUrl">jdbc:postgresql://localhost:5432/mydb</Set>
                <Set name="user">user</Set>
                <Set name="password">pass</Set>
            </New>
        </Arg>
    </New>
</Configure>

PostgreSQL JDBC driver version

<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <version>9.3-1101-jdbc41</version>
</dependency>

Packet capture

https://postimg.cc/image/gbl2dq4zx/

No.     Time           Source                Destination           Protocol Length Info
     12 0.175636000    127.0.0.1             127.0.0.1             PGSQL    182    >P/B/D/E/S

Frame 12: 182 bytes on wire (1456 bits), 182 bytes captured (1456 bits) on interface 0
PostgreSQL
    Type: Parse
    Length: 69
    Statement: 
    Query: SELECT "SECRET" FROM "user" WHERE "NAME" = $1 RETURNING *
    Parameters: 1
        Type OID: 1043

Answer 1

In my case occurred when u tried to insert empty list of objects.

Answer 2

The easiest way I've done this was adding ";--" at the end of sql code:

String sql = "INSERT INTO testTable(var1, var2) values ("1","2"), ("1","2") RETURNING id;--";

PreparedStatement ps = getConnection().prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
ps.executeUpdate();
ResultSet rs = ps.getGeneratedKeys();

Answer 3

This looks like a problem with sql2o. The comments on the bug report say:

Whe using PostgreSQL, all SELECT statements will fail with message: org.postgresql.util.PSQLException: ERROR: syntax error at or near "RETURNING"

Seems to be related to this issue

This has been fixed with version 1.1.2.

The fix requires the QuirkMode enum flag to be set to PostgreSQL when creating a new instance of sql2o. It changes default behaviour of queries to NOT fetch generated keys by default. When it is needed to fetch generated keys, the returnGeneratedKeys parameter in the generateQuery method should be set.

Since Sql2o 1.6.0, include the sql2o-postgres dependency and use new PostgresQuirks() instead of QuirksMode.