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da7a1dc0d6
Separate att_align_nominal() into two macros, similarly to what was already done with att_align_datum() and att_align_pointer(). The inner macro att_nominal_alignby() is really just TYPEALIGN(), while att_align_nominal() retains its previous API by mapping TYPALIGN_xxx values to numbers of bytes to align to and then calling att_nominal_alignby(). In support of this, split out tupdesc.c's logic to do that mapping into a publicly visible function typalign_to_alignby(). Having done that, we can replace performance-critical uses of att_align_nominal() with att_nominal_alignby(), where the typalign_to_alignby() mapping is done just once outside the loop. In most places I settled for doing typalign_to_alignby() once per function. We could in many places pass the alignby value in from the caller if we wanted to change function APIs for this purpose; but I'm a bit loath to do that, especially for exported APIs that extensions might call. Replacing a char typalign argument by a uint8 typalignby argument would be an API change that compilers would fail to warn about, thus silently breaking code in hard-to-debug ways. I did revise the APIs of array_iter_setup and array_iter_next, moving the element type attribute arguments to the former; if any external code uses those, the argument-count change will cause visible compile failures. Performance testing shows that ExecEvalScalarArrayOp is sped up by about 10% by this change, when using a simple per-element function such as int8eq. I did not check any of the other loops optimized here, but it's reasonable to expect similar gains. Although the motivation for creating this patch was to avoid a performance loss if we add some more typalign values, it evidently is worth doing whether that patch lands or not. Discussion: https://postgr.es/m/1127261.1769649624@sss.pgh.pa.us
127 lines
3.2 KiB
C
127 lines
3.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* arrayaccess.h
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* Declarations for element-by-element access to Postgres arrays.
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*
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*
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* Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/arrayaccess.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef ARRAYACCESS_H
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#define ARRAYACCESS_H
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#include "access/tupmacs.h"
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#include "utils/array.h"
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/*
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* Functions for iterating through elements of a flat or expanded array.
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* These require a state struct "array_iter iter".
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*
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* Use "array_iter_setup(&iter, arrayptr, ...);" to prepare to iterate,
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* and "datumvar = array_iter_next(&iter, &isnullvar, index);" to fetch
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* the next element into datumvar/isnullvar.
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* "index" must be the zero-origin element number; we make caller provide
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* this since caller is generally counting the elements anyway. Despite
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* that, these functions can only fetch elements sequentially.
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*/
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typedef struct array_iter
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{
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/* datumptr being NULL or not tells if we have flat or expanded array */
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/* Fields used when we have an expanded array */
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Datum *datumptr; /* Pointer to Datum array */
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bool *isnullptr; /* Pointer to isnull array */
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/* Fields used when we have a flat array */
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char *dataptr; /* Current spot in the data area */
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bits8 *bitmapptr; /* Current byte of the nulls bitmap, or NULL */
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int bitmask; /* mask for current bit in nulls bitmap */
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/* Fields used in both cases: data about array's element type */
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int elmlen;
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bool elmbyval;
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uint8 elmalignby;
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} array_iter;
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static inline void
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array_iter_setup(array_iter *it, AnyArrayType *a,
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int elmlen, bool elmbyval, char elmalign)
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{
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if (VARATT_IS_EXPANDED_HEADER(a))
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{
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if (a->xpn.dvalues)
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{
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it->datumptr = a->xpn.dvalues;
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it->isnullptr = a->xpn.dnulls;
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/* we must fill all fields to prevent compiler warnings */
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it->dataptr = NULL;
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it->bitmapptr = NULL;
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}
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else
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{
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/* Work with flat array embedded in the expanded datum */
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it->datumptr = NULL;
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it->isnullptr = NULL;
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it->dataptr = ARR_DATA_PTR(a->xpn.fvalue);
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it->bitmapptr = ARR_NULLBITMAP(a->xpn.fvalue);
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}
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}
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else
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{
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it->datumptr = NULL;
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it->isnullptr = NULL;
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it->dataptr = ARR_DATA_PTR((ArrayType *) a);
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it->bitmapptr = ARR_NULLBITMAP((ArrayType *) a);
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}
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it->bitmask = 1;
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it->elmlen = elmlen;
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it->elmbyval = elmbyval;
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it->elmalignby = typalign_to_alignby(elmalign);
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}
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static inline Datum
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array_iter_next(array_iter *it, bool *isnull, int i)
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{
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Datum ret;
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if (it->datumptr)
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{
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ret = it->datumptr[i];
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*isnull = it->isnullptr ? it->isnullptr[i] : false;
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}
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else
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{
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if (it->bitmapptr && (*(it->bitmapptr) & it->bitmask) == 0)
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{
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*isnull = true;
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ret = (Datum) 0;
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}
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else
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{
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*isnull = false;
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ret = fetch_att(it->dataptr, it->elmbyval, it->elmlen);
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it->dataptr = att_addlength_pointer(it->dataptr, it->elmlen,
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it->dataptr);
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it->dataptr = (char *) att_nominal_alignby(it->dataptr,
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it->elmalignby);
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}
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it->bitmask <<= 1;
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if (it->bitmask == 0x100)
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{
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if (it->bitmapptr)
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it->bitmapptr++;
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it->bitmask = 1;
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}
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}
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return ret;
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}
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#endif /* ARRAYACCESS_H */
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