Show a sensible value in pg_settings.unit for GUC_UNIT_XSEGS variables.

Commit 88e982302 invented GUC_UNIT_XSEGS for min_wal_size and max_wal_size,
but neglected to make it display sensibly in pg_settings.unit (by adding a
case to the switch in GetConfigOptionByNum).  Fix that, and adjust said
switch to throw a run-time error the next time somebody forgets.

In passing, avoid using a static buffer for the output string --- the rest
of this function pstrdup's from a local buffer, and I see no very good
reason why the units code should do it differently and less safely.

Per report from Otar Shavadze.  Back-patch to 9.5 where the new unit type
was added.

Report: <CAG-jOyA=iNFhN+yB4vfvqh688B7Tr5SArbYcFUAjZi=0Exp-Lg@mail.gmail.com>

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index cced814d6aba34d8abd8e579f8bf82508255f9c3..622279b058a0839ce97bb14c1cf5380591d46676 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -8016,20 +8016,23 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
        /* unit */
        if (conf->vartype == PGC_INT)
        {
-               static char buf[8];
-
                switch (conf->flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME))
                {
                        case GUC_UNIT_KB:
                                values[2] = "kB";
                                break;
                        case GUC_UNIT_BLOCKS:
-                               snprintf(buf, sizeof(buf), "%dkB", BLCKSZ / 1024);
-                               values[2] = buf;
+                               snprintf(buffer, sizeof(buffer), "%dkB", BLCKSZ / 1024);
+                               values[2] = pstrdup(buffer);
                                break;
                        case GUC_UNIT_XBLOCKS:
-                               snprintf(buf, sizeof(buf), "%dkB", XLOG_BLCKSZ / 1024);
-                               values[2] = buf;
+                               snprintf(buffer, sizeof(buffer), "%dkB", XLOG_BLCKSZ / 1024);
+                               values[2] = pstrdup(buffer);
+                               break;
+                       case GUC_UNIT_XSEGS:
+                               snprintf(buffer, sizeof(buffer), "%dMB",
+                                                XLOG_SEG_SIZE / (1024 * 1024));
+                               values[2] = pstrdup(buffer);
                                break;
                        case GUC_UNIT_MS:
                                values[2] = "ms";
@@ -8040,7 +8043,12 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
                        case GUC_UNIT_MIN:
                                values[2] = "min";
                                break;
+                       case 0:
+                               values[2] = NULL;
+                               break;
                        default:
+                               elog(ERROR, "unrecognized GUC units value: %d",
+                                        conf->flags & (GUC_UNIT_MEMORY | GUC_UNIT_TIME));
                                values[2] = NULL;
                                break;
                }

diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index e1de1a5d0653bdb72ecbdb6a92207f3e5e4fa3ea..0bf9f21067824daed538bb6ba477ddfda7686e78 100644 (file)
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -219,12 +219,12 @@ typedef enum
 #define GUC_UNIT_BLOCKS                        0x2000  /* value is in blocks */
 #define GUC_UNIT_XBLOCKS               0x3000  /* value is in xlog blocks */
 #define GUC_UNIT_XSEGS                 0x4000  /* value is in xlog segments */
-#define GUC_UNIT_MEMORY                        0xF000  /* mask for KB, BLOCKS, XBLOCKS */
+#define GUC_UNIT_MEMORY                        0xF000  /* mask for size-related units */
 
 #define GUC_UNIT_MS                       0x10000      /* value is in milliseconds */
 #define GUC_UNIT_S                        0x20000      /* value is in seconds */
 #define GUC_UNIT_MIN              0x30000      /* value is in minutes */
-#define GUC_UNIT_TIME             0xF0000      /* mask for MS, S, MIN */
+#define GUC_UNIT_TIME             0xF0000      /* mask for time-related units */
 
 #define GUC_UNIT                               (GUC_UNIT_MEMORY | GUC_UNIT_TIME)