Escaping hstore contains operators in a JDBC Prepared statement - postgresql

Question

I am using PostgreSQL 9.1.4 with hstore and the PostgreSQL JDBC driver (9.1-901.jdbc4).
I am trying to use the contains operators (?, ?&, ?|) in a PreparedStatement, however the ? character is parsed as a variable placeholder. Can this character be escaped to send the correct operator in the query?
An example:
PreparedStatement stmt = conn.prepareStatement("SELECT a, b FROM table1 WHERE c ? 'foo' AND d = ?");
stmt.setInt(1, dValue);
stmt.executeQuery();
In this form the following example would raise an exception:
org.postgresql.util.PSQLException: No value specified for parameter 2.
Update:
After investigating the query parser in the pgjdbc driver this snippet seems to indicate that it is not possible to escape the ? character. The questions that remain are:
Is there anything in the JDBC spec which allows a ? to be escaped and be anything other than a parameter placeholder?
Is there any better work around for this issue than just using plain Statements with variables manually inserted into the query string?

Answer 1

Effectively, it looks like the java SQL parser is not hstore compliant.
But since the syntax c ? 'foo' is equivalent to exist(c, 'foo'), you can easily workaround this problem. Have a look at the following page to see what the verbose operators for hstore are.
Postgres hstore documentation

Answer 2

There is a discussion about this issue on pgsql-hackers mailing list: http://grokbase.com/t/postgresql/pgsql-hackers/1325c6ys9n/alias-hstores-to-so-that-it-works-with-jdbc
For now I like most this workaround which also supports indexes:
CREATE FUNCTION exist_inline (hstore, text) RETURNS bool AS $$ SELECT $1 ? $2; $$ LANGUAGE sql;

Answer 3

You can use this query to find the function backing an operator in PostgreSQL like this. In your example:
SELECT
oprname,
oprcode || '(' || format_type(oprleft, NULL::integer) || ', '
|| format_type(oprright, NULL::integer) || ')' AS function
FROM pg_operator
WHERE oprname LIKE '?%'
AND (SELECT oid FROM pg_type WHERE typname = 'hstore') IN (oprleft, oprright);
This produces:
|oprname|function |
|-------|--------------------------|
|? |exist(hstore, text) |
|?| |exists_any(hstore, text[])|
|?& |exists_all(hstore, text[])|
See also a related question about using JSON operators containing ?. Note that the function usage may not profit from the same indexing capability when using a GIN index on your HSTORE column.

Answer 4

If you'd like to add multiple key-value pairs using PreparedStatement then you can do:
PreparedStatement ps = c.prepareStatement(
"insert into xyz(id, data) values(?, hstore(?, ?))");
ps.setLong(1, 23456L);
ps.setArray(2, c.createArrayOf("text", new String[]{"name", "city"}));
ps.setArray(3, c.createArrayOf("text", new String[]{"Duke", "Valley"}));
This will insert: 23456, 'name=>Duke, city=>Valley'