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XLOG_PAGE_MAGIC
XLOG_PAGE_MAGIC is a preprocessor constant embedded in the header of a WAL file defining its version.
XLOG_PAGE_MAGIC has been present since PostgreSQL 7.0 (although it has only been of practical use since the full introduction of WAL in PostgreSQL 7.1).
Source code
XLOG_PAGE_MAGIC is defined in src/include/access/xlog_internal.h (prior to PostgreSQL 8.0 in src/include/access/xlog.h.
Usage and values
XLOG_PAGE_MAGIC is a two-byte constant, which is incremented each time a change is made to the format of WAL files. There is no direct correlation to the PostgreSQL version number, but the value at the point of each stable PostgreSQL release since PostgreSQL 8.0 has been higher than the value at the point of the previous stable release, so it's theoretically possible to determine which PostgreSQL version a WAL file is associated with based on the value of XLOG_PAGE_MAGIC. Note that there was no increment between PostgreSQL 7.3 and PostgreSQL 7.4 (see table below).
| PostgreSQL version | XLOG_PAGE_MAGIC | Notes |
|---|---|---|
| PostgreSQL 14 | 0xD108 | not final |
| PostgreSQL 13 | 0xD106 | |
| PostgreSQL 12 | 0xD101 | |
| PostgreSQL 11 | 0xD098 | |
| PostgreSQL 10 | 0xD097 | |
| PostgreSQL 9.6 | 0xD093 | |
| PostgreSQL 9.5 | 0xD087 | |
| PostgreSQL 9.4 | 0xD07E | |
| PostgreSQL 9.3 | 0xD075 | |
| PostgreSQL 9.2 | 0xD071 | |
| PostgreSQL 9.1 | 0xD066 | |
| PostgreSQL 9.0 | 0xD064 | |
| PostgreSQL 8.4 | 0xD063 | |
| PostgreSQL 8.3 | 0xD062 | |
| PostgreSQL 8.2 | 0xD05E | |
| PostgreSQL 8.1 | 0xD05D | |
| PostgreSQL 8.0 | 0xD05C | moved to src/include/access/xlog_internal.h |
| PostgreSQL 7.4 | 0xD05A | same as PostgreSQL 7.3 |
| PostgreSQL 7.3 | 0xD05A | |
| PostgreSQL 7.2 | 0xD059 | |
| PostgreSQL 7.1 | 0xD058 | |
| PostgreSQL 7.0 | 0x17345168 | experimental |