From cdbb3921308ec71e7d090b734a1c8c0bf3269088 Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@postgresql.org>
Date: Thu, 17 Oct 2019 13:24:50 +1300
Subject: [PATCH] When restoring GUCs in parallel workers, show an error
context.
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
---
src/backend/utils/misc/guc.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 07447d35e3f..569439fec75 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9033,6 +9033,21 @@ 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
@@ -9051,6 +9066,7 @@ 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++)
@@ -9063,9 +9079,16 @@ 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);
@@ -9078,6 +9101,9 @@ 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)
@@ -9086,7 +9112,10 @@ 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;
}
/*
--
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