diff options
Diffstat (limited to 'src/include/access')
| -rw-r--r-- | src/include/access/hash.h | 32 |
1 files changed, 27 insertions, 5 deletions
diff --git a/src/include/access/hash.h b/src/include/access/hash.h index 72fce3038c0..c06dcb214f0 100644 --- a/src/include/access/hash.h +++ b/src/include/access/hash.h @@ -39,6 +39,17 @@ typedef uint32 Bucket; ((BlockNumber) ((B) + ((B) ? (metap)->hashm_spares[_hash_spareindex((B)+1)-1] : 0)) + 1) /* + * Rotate the high 32 bits and the low 32 bits separately. The standard + * hash function sometimes rotates the low 32 bits by one bit when + * combining elements. We want extended hash functions to be compatible with + * that algorithm when the seed is 0, so we can't just do a normal rotation. + * This works, though. + */ +#define ROTATE_HIGH_AND_LOW_32BITS(v) \ + ((((v) << 1) & UINT64CONST(0xfffffffefffffffe)) | \ + (((v) >> 31) & UINT64CONST(0x100000001))) + +/* * Special space for hash index pages. * * hasho_flag's LH_PAGE_TYPE bits tell us which type of page we're looking at. @@ -289,12 +300,20 @@ typedef HashMetaPageData *HashMetaPage; #define HTMaxStrategyNumber 1 /* - * When a new operator class is declared, we require that the user supply - * us with an amproc procudure for hashing a key of the new type. - * Since we only have one such proc in amproc, it's number 1. + * When a new operator class is declared, we require that the user supply + * us with an amproc procudure for hashing a key of the new type, returning + * a 32-bit hash value. We call this the "standard" hash procedure. We + * also allow an optional "extended" hash procedure which accepts a salt and + * returns a 64-bit hash value. This is highly recommended but, for reasons + * of backward compatibility, optional. + * + * When the salt is 0, the low 32 bits of the value returned by the extended + * hash procedure should match the value that would have been returned by the + * standard hash procedure. */ -#define HASHPROC 1 -#define HASHNProcs 1 +#define HASHSTANDARD_PROC 1 +#define HASHEXTENDED_PROC 2 +#define HASHNProcs 2 /* public routines */ @@ -322,7 +341,10 @@ extern bytea *hashoptions(Datum reloptions, bool validate); extern bool hashvalidate(Oid opclassoid); extern Datum hash_any(register const unsigned char *k, register int keylen); +extern Datum hash_any_extended(register const unsigned char *k, + register int keylen, uint64 seed); extern Datum hash_uint32(uint32 k); +extern Datum hash_uint32_extended(uint32 k, uint64 seed); /* private routines */ |