diff options
Diffstat (limited to 'src/backend/access/transam/xlog.c')
| -rw-r--r-- | src/backend/access/transam/xlog.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index d10704360a6..ea1f2d2993c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -4284,6 +4284,33 @@ WriteControlFile(void) ControlFile->float8ByVal = FLOAT8PASSBYVAL; + /* + * Initialize the default 'char' signedness. + * + * The signedness of the char type is implementation-defined. For instance + * on x86 architecture CPUs, the char data type is typically treated as + * signed by default, whereas on aarch architecture CPUs, it is typically + * treated as unsigned by default. In v17 or earlier, we accidentally let + * C implementation signedness affect persistent data. This led to + * inconsistent results when comparing char data across different + * platforms. + * + * This flag can be used as a hint to ensure consistent behavior for + * pre-v18 data files that store data sorted by the 'char' type on disk, + * especially in cross-platform replication scenarios. + * + * Newly created database clusters unconditionally set the default char + * signedness to true. pg_upgrade changes this flag for clusters that were + * initialized on signedness=false platforms. As a result, + * signedness=false setting will become rare over time. If we had known + * about this problem during the last development cycle that forced initdb + * (v8.3), we would have made all clusters signed or all clusters + * unsigned. Making pg_upgrade the only source of signedness=false will + * cause the population of database clusters to converge toward that + * retrospective ideal. + */ + ControlFile->default_char_signedness = true; + /* Contents are protected with a CRC */ INIT_CRC32C(ControlFile->crc); COMP_CRC32C(ControlFile->crc, @@ -4613,6 +4640,19 @@ DataChecksumsEnabled(void) } /* + * Return true if the cluster was initialized on a platform where the + * default signedness of char is "signed". This function exists for code + * that deals with pre-v18 data files that store data sorted by the 'char' + * type on disk (e.g., GIN and GiST indexes). See the comments in + * WriteControlFile() for details. + */ +bool +GetDefaultCharSignedness(void) +{ + return ControlFile->default_char_signedness; +} + +/* * Returns a fake LSN for unlogged relations. * * Each call generates an LSN that is greater than any previous value |