From 8782a84529035baca1639c3680458e2062ef9b44 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 4 Sep 2021 16:29:08 -0400 Subject: [PATCH] Further portability tweaks for float4/float8 hash functions. Attempting to make hashfloat4() look as much as possible like hashfloat8(), I'd figured I could replace NaNs with get_float4_nan() before widening to float8. However, results from protosciurus and topminnow show that on some platforms that produces a different bit-pattern from get_float8_nan(), breaking the intent of ce773f230. Rearrange so that we use the result of get_float8_nan() for all NaN cases. As before, back-patch. --- src/backend/access/hash/hashfunc.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/src/backend/access/hash/hashfunc.c b/src/backend/access/hash/hashfunc.c index 20f4e40893..accac104d5 100644 --- a/src/backend/access/hash/hashfunc.c +++ b/src/backend/access/hash/hashfunc.c @@ -152,14 +152,6 @@ hashfloat4(PG_FUNCTION_ARGS) if (key == (float4) 0) PG_RETURN_UINT32(0); - /* - * Similarly, NaNs can have different bit patterns but they should all - * compare as equal. For backwards-compatibility reasons we force them to - * have the hash value of a standard NaN. - */ - if (isnan(key)) - key = get_float4_nan(); - /* * To support cross-type hashing of float8 and float4, we want to return * the same hash value hashfloat8 would produce for an equal float8 value. @@ -169,6 +161,16 @@ hashfloat4(PG_FUNCTION_ARGS) */ key8 = key; + /* + * Similarly, NaNs can have different bit patterns but they should all + * compare as equal. For backwards-compatibility reasons we force them to + * have the hash value of a standard float8 NaN. (You'd think we could + * replace key with a float4 NaN and then widen it; but on some old + * platforms, that way produces a different bit pattern.) + */ + if (isnan(key8)) + key8 = get_float8_nan(); + return hash_any((unsigned char *) &key8, sizeof(key8)); } @@ -182,9 +184,9 @@ hashfloat4extended(PG_FUNCTION_ARGS) /* Same approach as hashfloat4 */ if (key == (float4) 0) PG_RETURN_UINT64(seed); - if (isnan(key)) - key = get_float4_nan(); key8 = key; + if (isnan(key8)) + key8 = get_float8_nan(); return hash_any_extended((unsigned char *) &key8, sizeof(key8), seed); }