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When restoring GUCs in parallel workers, show an error context.

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Otherwise it can be hard to see where an error is coming from, when
the parallel worker sets all the GUCs that it received from the
leader.  Bug #15726.  Back-patch to 9.5, where RestoreGUCState()
appeared.

Reported-by: Tiago Anastacio
Reviewed-by: Daniel Gustafsson, Tom Lane
Discussion: https://postgr.es/m/15726-6d67e4fa14f027b3%40postgresql.org
This commit is contained in:
Thomas Munro 2019-10-17 13:24:50 +13:00
parent 486a8f1522
commit 3af7c64fe7
1 changed files with 29 additions and 0 deletions
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29
src/backend/utils/misc/guc.c
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@ -10209,6 +10209,21 @@ read_gucstate_binary(char **srcptr, char *srcend, void *dest, Size size)
*srcptr += size;
}
/*
* Callback used to add a context message when reporting errors that occur
* while trying to restore GUCs in parallel workers.
*/
static void
guc_restore_error_context_callback(void *arg)
{
char **error_context_name_and_value = (char **) arg;
if (error_context_name_and_value)
errcontext("while setting parameter \"%s\" to \"%s\"",
error_context_name_and_value[0],
error_context_name_and_value[1]);
}
/*
* RestoreGUCState:
* Reads the GUC state at the specified address and updates the GUCs with the
@ -10227,6 +10242,7 @@ RestoreGUCState(void *gucstate)
char *srcend;
Size len;
int i;
ErrorContextCallback error_context_callback;
/* See comment at can_skip_gucvar(). */
for (i = 0; i < num_guc_variables; i++)
@ -10239,9 +10255,16 @@ RestoreGUCState(void *gucstate)
srcptr += sizeof(len);
srcend = srcptr + len;
/* If the GUC value check fails, we want errors to show useful context. */
error_context_callback.callback = guc_restore_error_context_callback;
error_context_callback.previous = error_context_stack;
error_context_callback.arg = NULL;
error_context_stack = &error_context_callback;
while (srcptr < srcend)
{
int result;
char *error_context_name_and_value[2];
varname = read_gucstate(&srcptr, srcend);
varvalue = read_gucstate(&srcptr, srcend);
@ -10256,6 +10279,9 @@ RestoreGUCState(void *gucstate)
read_gucstate_binary(&srcptr, srcend,
&varscontext, sizeof(varscontext));
error_context_name_and_value[0] = varname;
error_context_name_and_value[1] = varvalue;
error_context_callback.arg = &error_context_name_and_value[0];
result = set_config_option(varname, varvalue, varscontext, varsource,
GUC_ACTION_SET, true, ERROR, true);
if (result <= 0)
@ -10264,7 +10290,10 @@ RestoreGUCState(void *gucstate)
errmsg("parameter \"%s\" could not be set", varname)));
if (varsourcefile[0])
set_config_sourcefile(varname, varsourcefile, varsourceline);
error_context_callback.arg = NULL;
}
error_context_stack = error_context_callback.previous;
}
/*