#727 add explain plan of sql requests for Postgresql 16 or later

[evernat]

issue #727,
for reference, https://www.cybertec-postgresql.com/en/explain-generic-plan-postgresql-16/

In pgAdmin 4, generic explain plan works well, for example:

explain (generic_plan) select 'dummy' where $1 = $2

Unfortunately, after testing the code of this pull request with Postgresql 16.3 and jdbc driver 42.7.3, in the monitoring detail page of sql requests which includes ? parameters, there is an error coming from the database and so no explain plan:

org.postgresql.util.PSQLException: ERREUR: Bind message supplies 0 parameters, but prepared statement "" requires 2
        at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2725)
        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2412)
        at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:371)
        at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:502)
        at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:419)
        at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:341)
        at org.postgresql.jdbc.PgStatement.executeCachedSql(PgStatement.java:326)
        at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:302)
        at org.postgresql.jdbc.PgStatement.executeQuery(PgStatement.java:251)
	...
        at net.bull.javamelody.internal.model.DatabaseInformations.explainPlanFor(DatabaseInformations.java:374)
        at net.bull.javamelody.internal.web.html.HtmlCounterRequestGraphReport.writeSqlRequestExplainPlan(HtmlCounterRequestGraphReport.java:191)
        at net.bull.javamelody.internal.web.html.HtmlCounterRequestGraphReport.writeRequestAndGraphDetail(HtmlCounterRequestGraphReport.java:124)
        at net.bull.javamelody.internal.web.html.HtmlReport.writeRequestAndGraphDetail(HtmlReport.java:254)
        at net.bull.javamelody.internal.web.HtmlController.doRequestGraphAndDetail(HtmlController.java:150)
	...

[evernat]

For that error, I do not see a way from jdbc api so that Postgresql does not require parameters in generic explain plan, like it does from pgAdmin4.

[evernat]

I have finally found a way using internal classes of the postgresql driver 😄