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Commit56ff8b2

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Use a lookup table for units in pg_size_pretty and pg_size_bytes
We've grown 2 versions of pg_size_pretty over the years, one for BIGINTand one for NUMERIC. Both should output the same, but keeping them insync is harder than needed due to neither function sharing a source oftruth about which units to use and how to transition to the next largestunit.Here we add a static array which defines the units that we recognize andhave both pg_size_pretty and pg_size_pretty_numeric use it. This willmake adding any units in the future a very simple task.The table contains all information required to allow us to also modifypg_size_bytes to use the lookup table, so adjust that too.There are no behavioral changes here.Author: David RowleyReviewed-by: Dean Rasheed, Tom Lane, David ChristensenDiscussion:https://postgr.es/m/CAApHDvru1F7qsEVL-iOHeezJ+5WVxXnyD_Jo9nht+Eh85ekK-Q@mail.gmail.com
1 parent55fe609 commit56ff8b2

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-90
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1 file changed

+80
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‎src/backend/utils/adt/dbsize.c

Lines changed: 80 additions & 90 deletions
Original file line numberDiff line numberDiff line change
@@ -34,6 +34,27 @@
3434
/* Divide by two and round away from zero */
3535
#definehalf_rounded(x) (((x) + ((x) < 0 ? -1 : 1)) / 2)
3636

37+
/* Units used in pg_size_pretty functions. All units must be powers of 2 */
38+
structsize_pretty_unit
39+
{
40+
constchar*name;/* bytes, kB, MB, GB etc */
41+
uint32limit;/* upper limit, prior to half rounding after
42+
* converting to this unit. */
43+
boolround;/* do half rounding for this unit */
44+
uint8unitbits;/* (1 << unitbits) bytes to make 1 of this
45+
* unit */
46+
};
47+
48+
/* When adding units here also update the error message in pg_size_bytes */
49+
staticconststructsize_pretty_unitsize_pretty_units[]= {
50+
{"bytes",10*1024, false,0},
51+
{"kB",20*1024-1, true,10},
52+
{"MB",20*1024-1, true,20},
53+
{"GB",20*1024-1, true,30},
54+
{"TB",20*1024-1, true,40},
55+
{NULL,0, false,0}
56+
};
57+
3758
/* Return physical size of directory contents, or 0 if dir doesn't exist */
3859
staticint64
3960
db_dir_size(constchar*path)
@@ -535,41 +556,34 @@ pg_size_pretty(PG_FUNCTION_ARGS)
535556
{
536557
int64size=PG_GETARG_INT64(0);
537558
charbuf[64];
538-
int64limit=10*1024;
539-
int64limit2=limit*2-1;
559+
conststructsize_pretty_unit*unit;
540560

541-
if (Abs(size)<limit)
542-
snprintf(buf,sizeof(buf),INT64_FORMAT" bytes",size);
543-
else
561+
for (unit=size_pretty_units;unit->name!=NULL;unit++)
544562
{
545-
/*
546-
* We use divide instead of bit shifting so that behavior matches for
547-
* both positive and negative size values.
548-
*/
549-
size /= (1 <<9);/* keep one extra bit for rounding */
550-
if (Abs(size)<limit2)
551-
snprintf(buf,sizeof(buf),INT64_FORMAT" kB",
552-
half_rounded(size));
553-
else
563+
uint8bits;
564+
565+
/* use this unit if there are no more units or we're below the limit */
566+
if (unit[1].name==NULL||Abs(size)<unit->limit)
554567
{
555-
size /= (1 <<10);
556-
if (Abs(size)<limit2)
557-
snprintf(buf,sizeof(buf),INT64_FORMAT" MB",
558-
half_rounded(size));
559-
else
560-
{
561-
size /= (1 <<10);
562-
if (Abs(size)<limit2)
563-
snprintf(buf,sizeof(buf),INT64_FORMAT" GB",
564-
half_rounded(size));
565-
else
566-
{
567-
size /= (1 <<10);
568-
snprintf(buf,sizeof(buf),INT64_FORMAT" TB",
569-
half_rounded(size));
570-
}
571-
}
568+
if (unit->round)
569+
size=half_rounded(size);
570+
571+
snprintf(buf,sizeof(buf),INT64_FORMAT" %s",size,unit->name);
572+
break;
572573
}
574+
575+
/*
576+
* Determine the number of bits to use to build the divisor. We may
577+
* need to use 1 bit less than the difference between this and the
578+
* next unit if the next unit uses half rounding. Or we may need to
579+
* shift an extra bit if this unit uses half rounding and the next one
580+
* does not. We use division rather than shifting right by this
581+
* number of bits to ensure positive and negative values are rounded
582+
* in the same way.
583+
*/
584+
bits= (unit[1].unitbits-unit->unitbits- (unit[1].round== true)
585+
+ (unit->round== true));
586+
size /= ((int64)1) <<bits;
573587
}
574588

575589
PG_RETURN_TEXT_P(cstring_to_text(buf));
@@ -640,57 +654,35 @@ Datum
640654
pg_size_pretty_numeric(PG_FUNCTION_ARGS)
641655
{
642656
Numericsize=PG_GETARG_NUMERIC(0);
643-
Numericlimit,
644-
limit2;
645-
char*result;
646-
647-
limit=int64_to_numeric(10*1024);
648-
limit2=int64_to_numeric(10*1024*2-1);
657+
char*result=NULL;
658+
conststructsize_pretty_unit*unit;
649659

650-
if (numeric_is_less(numeric_absolute(size),limit))
660+
for (unit=size_pretty_units;unit->name!=NULL;unit++)
651661
{
652-
result=psprintf("%s bytes",numeric_to_cstring(size));
653-
}
654-
else
655-
{
656-
/* keep one extra bit for rounding */
657-
/* size /= (1 << 9) */
658-
size=numeric_truncated_divide(size,1 <<9);
662+
unsignedintshiftby;
659663

660-
if (numeric_is_less(numeric_absolute(size),limit2))
664+
/* use this unit if there are no more units or we're below the limit */
665+
if (unit[1].name==NULL||
666+
numeric_is_less(numeric_absolute(size),
667+
int64_to_numeric(unit->limit)))
661668
{
662-
size=numeric_half_rounded(size);
663-
result=psprintf("%s kB",numeric_to_cstring(size));
664-
}
665-
else
666-
{
667-
/* size /= (1 << 10) */
668-
size=numeric_truncated_divide(size,1 <<10);
669-
670-
if (numeric_is_less(numeric_absolute(size),limit2))
671-
{
669+
if (unit->round)
672670
size=numeric_half_rounded(size);
673-
result=psprintf("%s MB",numeric_to_cstring(size));
674-
}
675-
else
676-
{
677-
/* size /= (1 << 10) */
678-
size=numeric_truncated_divide(size,1 <<10);
679-
680-
if (numeric_is_less(numeric_absolute(size),limit2))
681-
{
682-
size=numeric_half_rounded(size);
683-
result=psprintf("%s GB",numeric_to_cstring(size));
684-
}
685-
else
686-
{
687-
/* size /= (1 << 10) */
688-
size=numeric_truncated_divide(size,1 <<10);
689-
size=numeric_half_rounded(size);
690-
result=psprintf("%s TB",numeric_to_cstring(size));
691-
}
692-
}
671+
672+
result=psprintf("%s %s",numeric_to_cstring(size),unit->name);
673+
break;
693674
}
675+
676+
/*
677+
* Determine the number of bits to use to build the divisor. We may
678+
* need to use 1 bit less than the difference between this and the
679+
* next unit if the next unit uses half rounding. Or we may need to
680+
* shift an extra bit if this unit uses half rounding and the next one
681+
* does not.
682+
*/
683+
shiftby= (unit[1].unitbits-unit->unitbits- (unit[1].round== true)
684+
+ (unit->round== true));
685+
size=numeric_truncated_divide(size, ((int64)1) <<shiftby);
694686
}
695687

696688
PG_RETURN_TEXT_P(cstring_to_text(result));
@@ -791,6 +783,7 @@ pg_size_bytes(PG_FUNCTION_ARGS)
791783
/* Handle possible unit */
792784
if (*strptr!='\0')
793785
{
786+
conststructsize_pretty_unit*unit;
794787
int64multiplier=0;
795788

796789
/* Trim any trailing whitespace */
@@ -802,21 +795,18 @@ pg_size_bytes(PG_FUNCTION_ARGS)
802795
endptr++;
803796
*endptr='\0';
804797

805-
/* Parse the unit case-insensitively */
806-
if (pg_strcasecmp(strptr,"bytes")==0)
807-
multiplier= (int64)1;
808-
elseif (pg_strcasecmp(strptr,"kb")==0)
809-
multiplier= (int64)1024;
810-
elseif (pg_strcasecmp(strptr,"mb")==0)
811-
multiplier= ((int64)1024)*1024;
812-
813-
elseif (pg_strcasecmp(strptr,"gb")==0)
814-
multiplier= ((int64)1024)*1024*1024;
815-
816-
elseif (pg_strcasecmp(strptr,"tb")==0)
817-
multiplier= ((int64)1024)*1024*1024*1024;
798+
for (unit=size_pretty_units;unit->name!=NULL;unit++)
799+
{
800+
/* Parse the unit case-insensitively */
801+
if (pg_strcasecmp(strptr,unit->name)==0)
802+
{
803+
multiplier= ((int64)1) <<unit->unitbits;
804+
break;
805+
}
806+
}
818807

819-
else
808+
/* Verify we found a valid unit in the loop above */
809+
if (unit->name==NULL)
820810
ereport(ERROR,
821811
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
822812
errmsg("invalid size: \"%s\"",text_to_cstring(arg)),

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