Re: [PATCHES] avg(int2) and avg(int8) micro-opt
Neil Conway wrote: Attached is a patch that applies the same optimization to int2_sum(), int4_sum(), float4_accum(), and float8_accum(). It wasn't possible to optimize do_numeric_accum() or int8_sum() since they both use numerics. Applied. -Neil ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [PATCHES] avg(int2) and avg(int8) micro-opt
Neil Conway wrote: Yeah, there might be some others we could improve. float4_accum() and float8_accum() look like they could be improved pretty easily, and do_numeric_accum() should also be fixable with some hackery. I suppose it's also worth optimizing int2_sum(), int4_sum() and int8_sum(). Attached is a patch that applies the same optimization to int2_sum(), int4_sum(), float4_accum(), and float8_accum(). It wasn't possible to optimize do_numeric_accum() or int8_sum() since they both use numerics. Performance gains are similar to those measured when this optimization has been applied to similar aggregates (e.g. avg(float8) goes from about 6400 ms to about 4300 ms on my machine, for a single column of float8 and about 1 million rows). Barring any objections, I'll apply this to HEAD tomorrow. -Neil Index: src/backend/utils/adt/float.c === RCS file: /Users/neilc/local/cvs/pgsql/src/backend/utils/adt/float.c,v retrieving revision 1.113 diff -c -r1.113 float.c *** src/backend/utils/adt/float.c 11 Feb 2005 04:08:58 - 1.113 --- src/backend/utils/adt/float.c 6 Apr 2005 07:24:38 - *** *** 1902,1909 float8 N, sumX, sumX2; - Datum transdatums[3]; - ArrayType *result; transvalues = check_float8_array(transarray, "float8_accum"); N = transvalues[0]; --- 1902,1907 *** *** 1914,1928 sumX += newval; sumX2 += newval * newval; ! transdatums[0] = Float8GetDatumFast(N); ! transdatums[1] = Float8GetDatumFast(sumX); ! transdatums[2] = Float8GetDatumFast(sumX2); ! ! result = construct_array(transdatums, 3, ! FLOAT8OID, ! sizeof(float8), false /* float8 byval */ , 'd'); ! PG_RETURN_ARRAYTYPE_P(result); } Datum --- 1912,1946 sumX += newval; sumX2 += newval * newval; ! /* ! * If we're invoked by nodeAgg, we can cheat and modify our first ! * parameter in-place to reduce palloc overhead. Otherwise we ! * construct a new array with the updated transition data and ! * return it. ! */ ! if (fcinfo->context && IsA(fcinfo->context, AggState)) ! { ! transvalues[0] = N; ! transvalues[1] = sumX; ! transvalues[2] = sumX2; ! ! PG_RETURN_ARRAYTYPE_P(transarray); ! } ! else ! { ! Datum transdatums[3]; ! ArrayType *result; ! ! transdatums[0] = Float8GetDatumFast(N); ! transdatums[1] = Float8GetDatumFast(sumX); ! transdatums[2] = Float8GetDatumFast(sumX2); ! ! result = construct_array(transdatums, 3, ! FLOAT8OID, ! sizeof(float8), false /* float8 byval */ , 'd'); ! PG_RETURN_ARRAYTYPE_P(result); ! } } Datum *** *** 1935,1942 sumX, sumX2, newval; - Datum transdatums[3]; - ArrayType *result; transvalues = check_float8_array(transarray, "float4_accum"); N = transvalues[0]; --- 1953,1958 *** *** 1950,1964 sumX += newval; sumX2 += newval * newval; ! transdatums[0] = Float8GetDatumFast(N); ! transdatums[1] = Float8GetDatumFast(sumX); ! transdatums[2] = Float8GetDatumFast(sumX2); ! ! result = construct_array(transdatums, 3, ! FLOAT8OID, ! sizeof(float8), false /* float8 byval */ , 'd'); ! PG_RETURN_ARRAYTYPE_P(result); } Datum --- 1966,2000 sumX += newval; sumX2 += newval * newval; ! /* ! * If we're invoked by nodeAgg, we can cheat and modify our first ! * parameter in-place to reduce palloc overhead. Otherwise we ! * construct a new array with the updated transition data and ! * return it. ! */ ! if (fcinfo->context && IsA(fcinfo->context, AggState)) ! { ! transvalues[0] = N; ! transvalues[1] = sumX; ! transvalues[2] = sumX2; ! ! PG_RETURN_ARRAYTYPE_P(transarray); ! } ! else ! { ! Datum transdatums[3]; ! ArrayType *result; ! ! transdatums[0] = Float8GetDatumFast(N); ! transdatums[1] = Float8GetDatumFast(sumX); ! transdatums[2] = Float8GetDatumFast(sumX2); ! ! result = construct_array(transdatums, 3, ! FLOAT8OID, ! sizeof(float8), false /* float8 byval */ , 'd'); ! PG_RETURN_ARRAYTYPE_P(result); ! } } Datum Index: src/backend/utils/adt/numeric.c === RCS file: /Users/neilc/local/cvs/pgsql/src/backend/utils/adt/numeric.c,v retrieving revision 1.82 diff -c -r1.82 numeric.c *** src/backend/utils/adt/numeric.c 4 Apr 2005 23:50:27 - 1.82 --- src/backend/utils/adt/numeric.c 6 Apr 2005 08:07:37 - *** *** 2357,2363 Datum int2_sum(PG_FUNCTION_ARGS) { - int64 oldsum; int64 newval; if (PG_ARGISNULL(0)) --- 2357,2362 *** *** 2370,2391 PG_RETURN_INT64(newval); } ! oldsum = PG_GETARG_INT64(0); ! /* Leave sum unchanged if new input is null. */ ! if (PG_ARGISNULL(1)) ! PG_RETURN_INT64(oldsum); ! /* OK to do the addition. */ ! newval = oldsum + (int64) PG_G
Re: [PATCHES] avg(int2) and avg(int8) micro-opt
Neil Conway <[EMAIL PROTECTED]> writes: > Tom Lane wrote: >> Why only those two? Might as well make all the accum functions look alike. > Yeah, there might be some others we could improve. float4_accum() and > float8_accum() look like they could be improved pretty easily, and > do_numeric_accum() should also be fixable with some hackery. I suppose > it's also worth optimizing int2_sum(), int4_sum() and int8_sum(). I'll > send a patch for this later today or tomorrow. Are there any other > transition functions where we can apply this technique? Actually, do_numeric_accum can't be fixed easily because numeric is a varlena type. The basic requirement for this hack is that the size of the transition value be constant ... regards, tom lane ---(end of broadcast)--- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
Re: [PATCHES] avg(int2) and avg(int8) micro-opt
Tom Lane wrote: Why only those two? Might as well make all the accum functions look alike. Yeah, there might be some others we could improve. float4_accum() and float8_accum() look like they could be improved pretty easily, and do_numeric_accum() should also be fixable with some hackery. I suppose it's also worth optimizing int2_sum(), int4_sum() and int8_sum(). I'll send a patch for this later today or tomorrow. Are there any other transition functions where we can apply this technique? BTW, int2_avg_accum() and int4_avg_accum() patch applied to HEAD. -Neil ---(end of broadcast)--- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
Re: [PATCHES] avg(int2) and avg(int8) micro-opt
Neil Conway <[EMAIL PROTECTED]> writes: > This patch changes int2_avg_accum() and int4_avg_accum() use the nodeAgg > performance hack Tom introduced recently. Why only those two? Might as well make all the accum functions look alike. > It is possible that the transition array might be TOAST'ed (not that I'd > expect that to occur in practice, of course). AFAICS that is impossible, since the transition value is never stored to disk. But your analysis is good anyway. regards, tom lane ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
[PATCHES] avg(int2) and avg(int8) micro-opt
This patch changes int2_avg_accum() and int4_avg_accum() use the nodeAgg performance hack Tom introduced recently. This means we can avoid copying the transition array for each input tuple if these functions are invoked as aggregate transition functions. To test the performance improvement, I created a 1 million row table with a single int4 column. Without the patch, SELECT avg(col) FROM table took about 4.2 seconds (after the data was cached); with the patch, it took about 3.2 seconds. Naturally, the performance improvement for a less trivial query (or a table with wider rows) would be relatively smaller. It is possible that the transition array might be TOAST'ed (not that I'd expect that to occur in practice, of course). The aggregates should continue to work in this case: PG_DETOAST_DATUM() is equivalent to PG_DETOAST_DATUM_COPY() if the datum is toast'ed, so in effect we just won't implement the nodeAgg performance hack if the transition array is toasted. If I've mucked this up, let me know. Barring any objections, I'll commit this tomorrow. -Neil Index: src/backend/utils/adt/numeric.c === RCS file: /Users/neilc/local/cvs/pgsql/src/backend/utils/adt/numeric.c,v retrieving revision 1.81 diff -c -r1.81 numeric.c *** src/backend/utils/adt/numeric.c 1 Jan 2005 05:43:07 - 1.81 --- src/backend/utils/adt/numeric.c 4 Apr 2005 11:00:41 - *** *** 2462,2478 Datum int2_avg_accum(PG_FUNCTION_ARGS) { ! ArrayType *transarray = PG_GETARG_ARRAYTYPE_P_COPY(0); int16 newval = PG_GETARG_INT16(1); Int8TransTypeData *transdata; /* ! * We copied the input array, so it's okay to scribble on it directly. */ if (ARR_SIZE(transarray) != ARR_OVERHEAD(1) + sizeof(Int8TransTypeData)) elog(ERROR, "expected 2-element int8 array"); - transdata = (Int8TransTypeData *) ARR_DATA_PTR(transarray); transdata->count++; transdata->sum += newval; --- 2462,2485 Datum int2_avg_accum(PG_FUNCTION_ARGS) { ! ArrayType *transarray; int16 newval = PG_GETARG_INT16(1); Int8TransTypeData *transdata; /* ! * If we're invoked by nodeAgg, we can cheat and modify our first ! * parameter in-place to reduce palloc overhead. Otherwise we need ! * to make a copy of it before scribbling on it. */ + if (fcinfo->context && IsA(fcinfo->context, AggState)) + transarray = PG_GETARG_ARRAYTYPE_P(0); + else + transarray = PG_GETARG_ARRAYTYPE_P_COPY(0); + if (ARR_SIZE(transarray) != ARR_OVERHEAD(1) + sizeof(Int8TransTypeData)) elog(ERROR, "expected 2-element int8 array"); + transdata = (Int8TransTypeData *) ARR_DATA_PTR(transarray); transdata->count++; transdata->sum += newval; *** *** 2482,2498 Datum int4_avg_accum(PG_FUNCTION_ARGS) { ! ArrayType *transarray = PG_GETARG_ARRAYTYPE_P_COPY(0); int32 newval = PG_GETARG_INT32(1); Int8TransTypeData *transdata; /* ! * We copied the input array, so it's okay to scribble on it directly. */ if (ARR_SIZE(transarray) != ARR_OVERHEAD(1) + sizeof(Int8TransTypeData)) elog(ERROR, "expected 2-element int8 array"); - transdata = (Int8TransTypeData *) ARR_DATA_PTR(transarray); transdata->count++; transdata->sum += newval; --- 2489,2512 Datum int4_avg_accum(PG_FUNCTION_ARGS) { ! ArrayType *transarray; int32 newval = PG_GETARG_INT32(1); Int8TransTypeData *transdata; /* ! * If we're invoked by nodeAgg, we can cheat and modify our first ! * parameter in-place to reduce palloc overhead. Otherwise we need ! * to make a copy of it before scribbling on it. */ + if (fcinfo->context && IsA(fcinfo->context, AggState)) + transarray = PG_GETARG_ARRAYTYPE_P(0); + else + transarray = PG_GETARG_ARRAYTYPE_P_COPY(0); + if (ARR_SIZE(transarray) != ARR_OVERHEAD(1) + sizeof(Int8TransTypeData)) elog(ERROR, "expected 2-element int8 array"); + transdata = (Int8TransTypeData *) ARR_DATA_PTR(transarray); transdata->count++; transdata->sum += newval; ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org