PostgreSQL syntax check without running the query

Question

I want to verify the syntax of files containing sql queries before they can be committed in my CVS project.

In order to do that, I have a commitinfo script, but I have trouble finding out if the sql commands are valid. psql does not seem to have a dryrun mode, and constructing my own postgresql-dialact tester from the grammar (that is in the source) seems like a long stretch.

The scripts may contain multiple queries, so an EXPLAIN cannot be wrapped around them.

Any hints?

Answer 1

I recently wrote up a utility to statically check the syntax of SQL for PostgreSQL. It leverages ecpg, the embedded SQL C preproccessor for postgres, to check the SQL syntax, so it uses the exact same parser that is built in to Postgres itself.

You can check it out on github: http://github.com/markdrago/pgsanity. You can give the README a skim to get a better idea of how it works and to get directions for how to install it. Here's a short example of how pgsanity can be used:

$ pgsanity good1.sql good2.sql bad.sql
bad.sql: line 1: ERROR: syntax error at or near "bogus_token"

$ find -name '*.sql' | xargs pgsanity
./sql/bad1.sql: line 59: ERROR: syntax error at or near ";"
./sql/bad2.sql: line 41: ERROR: syntax error at or near "insert"
./sql/bad3.sql: line 57: ERROR: syntax error at or near "update"

Answer 2

One way would be to put it into a transaction that you roll back at the end:

BEGIN;
<query>;
<query>;
<query>;
ROLLBACK;

Be aware that there are some effects that cannot be rolled back, like dblink calls, or anything written to the file system or incremented sequences.

I would advise cloning your database for testing purposes.

Answer 3

I'm usually use Mimer online SQL validator, the only thing is that it check SQL syntax for standard SQL :

• SQL-92
• SQL-99
• SQL-03

and not specific for the PostgreSQL ... However if you write code following the standard you can use it and it work well ...

Answer 4

EXPLAIN (without ANALYZE) will parse the query and prepare an execution plan, without actually executing it.

https://www.postgresql.org/docs/current/static/sql-explain.html

Answer 5

A wonderful utility to verify SQL syntax: SQL Fiddle

Supports MySQL, Oracle, PostgreSQL, SQLite, MS SQL.

Answer 6

You could just wrap it in SELECT 1 ( <your query> ) AS a WHERE 1 = 0;

It'll fail on validation but it won't actually execute. Here's an example query plan:

Result  (cost=0.00..0.01 rows=1 width=0)
  One-Time Filter: false

Answer 7

You can run queries iside postgresql function and raise exception in the end. All changes will be rolled back. For example:

CREATE OR REPLACE FUNCTION run_test(_sp character varying)
  RETURNS character varying AS
$BODY$
BEGIN
  EXECUTE 'SELECT ' || _sp;
  RAISE EXCEPTION '#OK';
EXCEPTION
  WHEN others THEN
    RETURN SQLERRM;
END;
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;

Another sollution - plpgsql_check extension (on github), the next incarnation of pgpsql_lint