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Adjust tuplestore stats API

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1eff8279d added an API to tuplestore.c to allow callers to obtain
storage telemetry data.  That API wasn't quite good enough for callers
that perform tuplestore_clear() as the telemetry functions only
accounted for the current state of the tuplestore, not the maximums
before tuplestore_clear() was called.

There's a pending patch that would like to add tuplestore telemetry
output to EXPLAIN ANALYZE for WindowAgg.  That node type uses
tuplestore_clear() before moving to the next window partition and we
want to show the maximum space used, not the space used for the final
partition.

Reviewed-by: Tatsuo Ishii, Ashutosh Bapat
Discussion: https://postgres/m/CAApHDvoY8cibGcicLV0fNh=9JVx9PANcWvhkdjBnDCc9Quqytg@mail.gmail.com
This commit is contained in:
David Rowley
2024-09-12 16:02:01 +12:00
parent e6c45d85dc
commit 9fba1ed294
3 changed files with 48 additions and 38 deletions
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64
src/backend/utils/sort/tuplestore.c
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@@ -107,9 +107,10 @@ struct Tuplestorestate
bool backward; /* store extra length words in file? */
bool interXact; /* keep open through transactions? */
bool truncated; /* tuplestore_trim has removed tuples? */
bool usedDisk; /* used by tuplestore_get_stats() */
int64 maxSpace; /* used by tuplestore_get_stats() */
int64 availMem; /* remaining memory available, in bytes */
int64 allowedMem; /* total memory allowed, in bytes */
int64 maxSpace; /* maximum space used in memory */
int64 tuples; /* number of tuples added */
BufFile *myfile; /* underlying file, or NULL if none */
MemoryContext context; /* memory context for holding tuples */
@@ -262,9 +263,10 @@ tuplestore_begin_common(int eflags, bool interXact, int maxKBytes)
state->eflags = eflags;
state->interXact = interXact;
state->truncated = false;
state->usedDisk = false;
state->maxSpace = 0;
state->allowedMem = maxKBytes * 1024L;
state->availMem = state->allowedMem;
state->maxSpace = 0;
state->myfile = NULL;
/*
@@ -870,6 +872,14 @@ tuplestore_puttuple_common(Tuplestorestate *state, void *tuple)
* though callers might drop the requirement.
*/
state->backward = (state->eflags & EXEC_FLAG_BACKWARD) != 0;
/*
* Update the maximum space used before dumping the tuples. It's
* possible that more space will be used by the tuples in memory
* than the space that will be used on disk.
*/
tuplestore_updatemax(state);
state->status = TSS_WRITEFILE;
dumptuples(state);
break;
@@ -1444,7 +1454,7 @@ tuplestore_trim(Tuplestorestate *state)
Assert(nremove >= state->memtupdeleted);
Assert(nremove <= state->memtupcount);
/* before freeing any memory, update maxSpace */
/* before freeing any memory, update the statistics */
tuplestore_updatemax(state);
/* Release no-longer-needed tuples */
@@ -1491,7 +1501,8 @@ tuplestore_trim(Tuplestorestate *state)
/*
* tuplestore_updatemax
* Update maxSpace field
* Update the maximum space used by this tuplestore and the method used
* for storage.
*/
static void
tuplestore_updatemax(Tuplestorestate *state)
@@ -1499,37 +1510,37 @@ tuplestore_updatemax(Tuplestorestate *state)
if (state->status == TSS_INMEM)
state->maxSpace = Max(state->maxSpace,
state->allowedMem - state->availMem);
}
/*
* tuplestore_storage_type_name
* Return a string description of the storage method used to store the
* tuples.
*/
const char *
tuplestore_storage_type_name(Tuplestorestate *state)
{
if (state->status == TSS_INMEM)
return "Memory";
else
return "Disk";
{
state->maxSpace = Max(state->maxSpace,
BufFileSize(state->myfile));
/*
* usedDisk never gets set to false again after spilling to disk, even
* if tuplestore_clear() is called and new tuples go to memory again.
*/
state->usedDisk = true;
}
}
/*
* tuplestore_space_used
* Return the maximum space used in memory unless the tuplestore has spilled
* to disk, in which case, return the disk space used.
* tuplestore_get_stats
* Obtain statistics about the maximum space used by the tuplestore.
* These statistics are the maximums and are not reset by calls to
* tuplestore_trim() or tuplestore_clear().
*/
int64
tuplestore_space_used(Tuplestorestate *state)
void
tuplestore_get_stats(Tuplestorestate *state, char **max_storage_type,
int64 *max_space)
{
/* First, update the maxSpace field */
tuplestore_updatemax(state);
if (state->status == TSS_INMEM)
return state->maxSpace;
if (state->usedDisk)
*max_storage_type = "Disk";
else
return BufFileSize(state->myfile);
*max_storage_type = "Memory";
*max_space = state->maxSpace;
}
/*
@@ -1601,7 +1612,6 @@ writetup_heap(Tuplestorestate *state, void *tup)
if (state->backward) /* need trailing length word? */
BufFileWrite(state->myfile, &tuplen, sizeof(tuplen));
/* no need to call tuplestore_updatemax() when not in TSS_INMEM */
FREEMEM(state, GetMemoryChunkSpace(tuple));
heap_free_minimal_tuple(tuple);
}