Method handle_explain

nodedb/src/control/server/pgwire/handler/session_cmds.rs:538–646

Handle EXPLAIN: plan the inner SQL and return the plan description.

(
        &self,
        identity: &AuthenticatedIdentity,
        addr: &std::net::SocketAddr,
        sql: &str,
    )

    /// Handle EXPLAIN: plan the inner SQL and return the plan description.
    pub(super) async fn handle_explain(
        &self,
        identity: &AuthenticatedIdentity,
        addr: &std::net::SocketAddr,
        sql: &str,
    ) -> PgWireResult<Vec<Response>> {
        let upper = sql.to_uppercase();
        let is_analyze = upper.starts_with("EXPLAIN ANALYZE ");

        let inner_sql = if is_analyze {
            sql[16..].trim()
        } else if upper.starts_with("EXPLAIN ") {
            sql[8..].trim()
        } else {
            return Err(PgWireError::UserError(Box::new(ErrorInfo::new(
                "ERROR".to_owned(),
                "42601".to_owned(),
                "syntax error in EXPLAIN".to_owned(),
            ))));
        };

        let database_id = self
            .sessions
            .get_current_database(addr)
            .unwrap_or(crate::types::DatabaseId::DEFAULT);
        if super::super::ddl::dispatch(&self.state, identity, inner_sql, database_id)
            .await
            .is_some()
        {
            let schema = Arc::new(vec![text_field("QUERY PLAN")]);
            let plan_text = format!(
                "DDL: {}",
                inner_sql
                    .split_whitespace()
                    .take(3)
                    .collect::<Vec<_>>()
                    .join(" ")
            );
            let mut encoder = DataRowEncoder::new(schema.clone());
            encoder.encode_field(&plan_text)?;
            let row = encoder.take_row();
            return Ok(vec![Response::Query(QueryResponse::new(
                schema,
                futures::stream::iter(vec![Ok(row)]),
            ))]);
        }

        let tenant_id = identity.tenant_id;
        let auth_ctx = crate::control::server::session_auth::build_auth_context(identity);
        let perm_cache = self.state.permission_cache.read().await;
        let sec = crate::control::planner::context::PlanSecurityContext {
            identity,
            auth: &auth_ctx,
            rls_store: &self.state.rls,
            permissions: &self.state.permissions,
            roles: &self.state.roles,
            permission_cache: Some(&*perm_cache),
        };