StartupXLOG() still has ThisTimeLineID as a local variable, but the
remaining code in xlog.c now needs to the relevant TimeLineID by some
other means. Mostly, this means that we now pass it as a function
parameter to a bunch of functions where we didn't previously.
However, a few cases require special handling:
- In functions that might be called by outside callers who
wouldn't necessarily know what timeline to specify, we get
the timeline ID from shared memory. XLogCtl->ThisTimeLineID
can be used in most cases since recovery is known to have
completed by the time those functions are called. In
xlog_redo(), we can use XLogCtl->replayEndTLI.
- XLogFileClose() needs to know the TLI of the open logfile.
Do that with a new global variable openLogTLI. While
someone could argue that this is just trading one global
variable for another, the new one has a far more narrow
purposes and is referenced in just a few places.
- read_backup_label() now returns the TLI that it obtains
by parsing the backup_label file. Previously, ReadRecord()
could be called to parse the checkpoint record without
ThisTimeLineID having been initialized. Now, the timeline
is passed down, and I didn't want to pass an uninitialized
variable; this change lets us avoid that. The old coding
didn't seem to have any practical consequences that we need
to worry about, but this is cleaner.
- In BootstrapXLOG(), it's just a constant.
Patch by me, reviewed and tested by Michael Paquier, Amul Sul, and
Álvaro Herrera.
Discussion: https://postgr.es/m/CA+TgmobfAAqhfWa1kaFBBFvX+5CjM=7TE=n4r4Q1o2bjbGYBpA@mail.gmail.com
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