From 5f89bb4cf0109bdb36eb8f78943f5b0f141c614a Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Wed, 15 Jul 2020 15:17:32 +0900 Subject: [PATCH] Fix handling of missing files when using pg_rewind with online source When working with an online source cluster, pg_rewind gets a list of all the files in the source data directory using a WITH RECURSIVE query, returning a NULL result for a file's metadata if it gets removed between the moment it is listed in a directory and the moment its metadata is obtained with pg_stat_file() (say a recycled WAL segment). The query result was processed in such a way that for each tuple we checked only that the first file's metadata was NULL. This could have two consequences, both resulting in a failure of the rewind: - If the first tuple referred to a removed file, all files from the source would be ignored. - Any file actually missing would not be considered as such. While on it, rework slightly the code so as no values are saved if we know that a file is going to be skipped. Issue introduced by b36805f, so backpatch down to 9.5. Author: Justin Pryzby, Michael Paquier Reviewed-by: Daniel Gustafsson, Masahiko Sawada Discussion: https://postgr.es/m/20200713061010.GC23581@telsasoft.com Backpatch-through: 9.5 --- src/bin/pg_rewind/libpq_fetch.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/src/bin/pg_rewind/libpq_fetch.c b/src/bin/pg_rewind/libpq_fetch.c index 1dbbceab0b..c44648f823 100644 --- a/src/bin/pg_rewind/libpq_fetch.c +++ b/src/bin/pg_rewind/libpq_fetch.c @@ -214,13 +214,13 @@ libpqProcessFileList(void) /* Read result to local variables */ for (i = 0; i < PQntuples(res); i++) { - char *path = PQgetvalue(res, i, 0); - int64 filesize = atol(PQgetvalue(res, i, 1)); - bool isdir = (strcmp(PQgetvalue(res, i, 2), "t") == 0); - char *link_target = PQgetvalue(res, i, 3); + char *path; + int64 filesize; + bool isdir; + char *link_target; file_type_t type; - if (PQgetisnull(res, 0, 1)) + if (PQgetisnull(res, i, 1)) { /* * The file was removed from the server while the query was @@ -229,6 +229,11 @@ libpqProcessFileList(void) continue; } + path = PQgetvalue(res, i, 0); + filesize = atol(PQgetvalue(res, i, 1)); + isdir = (strcmp(PQgetvalue(res, i, 2), "t") == 0); + link_target = PQgetvalue(res, i, 3); + if (link_target[0]) type = FILE_TYPE_SYMLINK; else if (isdir)