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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 BIGINT
and one for NUMERIC.  Both should output the same, but keeping them in
sync is harder than needed due to neither function sharing a source of
truth about which units to use and how to transition to the next largest
unit.

Here we add a static array which defines the units that we recognize and
have both pg_size_pretty and pg_size_pretty_numeric use it.  This will
make adding any units in the future a very simple task.

The table contains all information required to allow us to also modify
pg_size_bytes to use the lookup table, so adjust that too.

There are no behavioral changes here.

Author: David Rowley
Reviewed-by: Dean Rasheed, Tom Lane, David Christensen
Discussion: https://postgr.es/m/CAApHDvru1F7qsEVL-iOHeezJ+5WVxXnyD_Jo9nht+Eh85ekK-Q@mail.gmail.com
This commit is contained in:
David Rowley 2021-07-09 16:29:02 +12:00
parent 55fe609387
commit 56ff8b2991
1 changed files with 79 additions and 89 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

168
src/backend/utils/adt/dbsize.c
View File

@ -34,6 +34,27 @@
/* Divide by two and round away from zero */
#define half_rounded(x) (((x) + ((x) < 0 ? -1 : 1)) / 2)
/* Units used in pg_size_pretty functions. All units must be powers of 2 */
struct size_pretty_unit
{
const char *name; /* bytes, kB, MB, GB etc */
uint32 limit; /* upper limit, prior to half rounding after
* converting to this unit. */
bool round; /* do half rounding for this unit */
uint8 unitbits; /* (1 << unitbits) bytes to make 1 of this
* unit */
};
/* When adding units here also update the error message in pg_size_bytes */
static const struct size_pretty_unit size_pretty_units[] = {
{"bytes", 10 * 1024, false, 0},
{"kB", 20 * 1024 - 1, true, 10},
{"MB", 20 * 1024 - 1, true, 20},
{"GB", 20 * 1024 - 1, true, 30},
{"TB", 20 * 1024 - 1, true, 40},
{NULL, 0, false, 0}
};
/* Return physical size of directory contents, or 0 if dir doesn't exist */
static int64
db_dir_size(const char *path)
@ -535,41 +556,34 @@ pg_size_pretty(PG_FUNCTION_ARGS)
{
int64 size = PG_GETARG_INT64(0);
char buf[64];
int64 limit = 10 * 1024;
int64 limit2 = limit * 2 - 1;
const struct size_pretty_unit *unit;
if (Abs(size) < limit)
snprintf(buf, sizeof(buf), INT64_FORMAT " bytes", size);
else
for (unit = size_pretty_units; unit->name != NULL; unit++)
{
/*
* We use divide instead of bit shifting so that behavior matches for
* both positive and negative size values.
*/
size /= (1 << 9); /* keep one extra bit for rounding */
if (Abs(size) < limit2)
snprintf(buf, sizeof(buf), INT64_FORMAT " kB",
half_rounded(size));
else
uint8 bits;
/* use this unit if there are no more units or we're below the limit */
if (unit[1].name == NULL || Abs(size) < unit->limit)
{
size /= (1 << 10);
if (Abs(size) < limit2)
snprintf(buf, sizeof(buf), INT64_FORMAT " MB",
half_rounded(size));
else
{
size /= (1 << 10);
if (Abs(size) < limit2)
snprintf(buf, sizeof(buf), INT64_FORMAT " GB",
half_rounded(size));
else
{
size /= (1 << 10);
snprintf(buf, sizeof(buf), INT64_FORMAT " TB",
half_rounded(size));
}
}
if (unit->round)
size = half_rounded(size);
snprintf(buf, sizeof(buf), INT64_FORMAT " %s", size, unit->name);
break;
}
/*
* Determine the number of bits to use to build the divisor. We may
* need to use 1 bit less than the difference between this and the
* next unit if the next unit uses half rounding. Or we may need to
* shift an extra bit if this unit uses half rounding and the next one
* does not. We use division rather than shifting right by this
* number of bits to ensure positive and negative values are rounded
* in the same way.
*/
bits = (unit[1].unitbits - unit->unitbits - (unit[1].round == true)
+ (unit->round == true));
size /= ((int64) 1) << bits;
}
PG_RETURN_TEXT_P(cstring_to_text(buf));
@ -640,57 +654,35 @@ Datum
pg_size_pretty_numeric(PG_FUNCTION_ARGS)
{
Numeric size = PG_GETARG_NUMERIC(0);
Numeric limit,
limit2;
char *result;
char *result = NULL;
const struct size_pretty_unit *unit;
limit = int64_to_numeric(10 * 1024);
limit2 = int64_to_numeric(10 * 1024 * 2 - 1);
if (numeric_is_less(numeric_absolute(size), limit))
for (unit = size_pretty_units; unit->name != NULL; unit++)
{
result = psprintf("%s bytes", numeric_to_cstring(size));
}
else
{
/* keep one extra bit for rounding */
/* size /= (1 << 9) */
size = numeric_truncated_divide(size, 1 << 9);
unsigned int shiftby;
if (numeric_is_less(numeric_absolute(size), limit2))
/* use this unit if there are no more units or we're below the limit */
if (unit[1].name == NULL ||
numeric_is_less(numeric_absolute(size),
int64_to_numeric(unit->limit)))
{
size = numeric_half_rounded(size);
result = psprintf("%s kB", numeric_to_cstring(size));
}
else
{
/* size /= (1 << 10) */
size = numeric_truncated_divide(size, 1 << 10);
if (numeric_is_less(numeric_absolute(size), limit2))
{
if (unit->round)
size = numeric_half_rounded(size);
result = psprintf("%s MB", numeric_to_cstring(size));
}
else
{
/* size /= (1 << 10) */
size = numeric_truncated_divide(size, 1 << 10);
if (numeric_is_less(numeric_absolute(size), limit2))
{
size = numeric_half_rounded(size);
result = psprintf("%s GB", numeric_to_cstring(size));
}
else
{
/* size /= (1 << 10) */
size = numeric_truncated_divide(size, 1 << 10);
size = numeric_half_rounded(size);
result = psprintf("%s TB", numeric_to_cstring(size));
}
}
result = psprintf("%s %s", numeric_to_cstring(size), unit->name);
break;
}
/*
* Determine the number of bits to use to build the divisor. We may
* need to use 1 bit less than the difference between this and the
* next unit if the next unit uses half rounding. Or we may need to
* shift an extra bit if this unit uses half rounding and the next one
* does not.
*/
shiftby = (unit[1].unitbits - unit->unitbits - (unit[1].round == true)
+ (unit->round == true));
size = numeric_truncated_divide(size, ((int64) 1) << shiftby);
}
PG_RETURN_TEXT_P(cstring_to_text(result));
@ -791,6 +783,7 @@ pg_size_bytes(PG_FUNCTION_ARGS)
/* Handle possible unit */
if (*strptr != '\0')
{
const struct size_pretty_unit *unit;
int64 multiplier = 0;
/* Trim any trailing whitespace */
@ -802,21 +795,18 @@ pg_size_bytes(PG_FUNCTION_ARGS)
endptr++;
*endptr = '\0';
/* Parse the unit case-insensitively */
if (pg_strcasecmp(strptr, "bytes") == 0)
multiplier = (int64) 1;
else if (pg_strcasecmp(strptr, "kb") == 0)
multiplier = (int64) 1024;
else if (pg_strcasecmp(strptr, "mb") == 0)
multiplier = ((int64) 1024) * 1024;
for (unit = size_pretty_units; unit->name != NULL; unit++)
{
/* Parse the unit case-insensitively */
if (pg_strcasecmp(strptr, unit->name) == 0)
{
multiplier = ((int64) 1) << unit->unitbits;
break;
}
}
else if (pg_strcasecmp(strptr, "gb") == 0)
multiplier = ((int64) 1024) * 1024 * 1024;
else if (pg_strcasecmp(strptr, "tb") == 0)
multiplier = ((int64) 1024) * 1024 * 1024 * 1024;
else
/* Verify we found a valid unit in the loop above */
if (unit->name == NULL)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("invalid size: \"%s\"", text_to_cstring(arg)),