Add client connection check during the execution of the query

2019-08-01 06:15:30 Thomas Munro (macdice) Closed in commitfest 2019-07 with status: Returned with feedback 2019-07-05 05:55:53 Thomas Munro (macdice) New status: Waiting on Author 2019-04-30 07:40:57 Sergey Cherkashin (cherkashins) Closed in commitfest 2019-01 with status: Moved to next CF 2019-03-05 13:32:11 Sergey Cherkashin (cherkashins) New status: Needs review 2019-01-31 13:56:15 Andres Freund (andresfreund) Closed in commitfest 2019-01 with status: Returned with feedback 2019-01-13 23:05:54 Tom Lane (tgl) New status: Waiting on Author 2018-11-19 15:27:40 Sergey Cherkashin (cherkashins) Changed authors to Sergey Cherkashin (cherkashins) 2018-11-19 15:27:40 Sergey Cherkashin (cherkashins) Changed reviewers to Stas Kelvich (kelvich) 2018-11-19 15:26:37 Sergey Cherkashin (cherkashins) Attached mail thread 77def86b27e41f0efcba411460e929ae@postgrespro.ru 2018-11-19 15:26:37 Sergey Cherkashin (cherkashins) Created patch record