diff options
Diffstat (limited to 'src/backend/access/common/detoast.c')
| -rw-r--r-- | src/backend/access/common/detoast.c | 33 |
1 files changed, 26 insertions, 7 deletions
diff --git a/src/backend/access/common/detoast.c b/src/backend/access/common/detoast.c index 44c37edcbb4..3d02d2b586c 100644 --- a/src/backend/access/common/detoast.c +++ b/src/backend/access/common/detoast.c @@ -17,6 +17,7 @@ #include "access/table.h" #include "access/tableam.h" #include "access/toast_internals.h" +#include "common/int.h" #include "common/pg_lzcompress.h" #include "utils/expandeddatum.h" #include "utils/rel.h" @@ -196,7 +197,8 @@ detoast_attr(struct varlena *attr) * Public entry point to get back part of a toasted value * from compression or external storage. * - * Note: When slicelength is negative, return suffix of the value. + * sliceoffset is where to start (zero or more) + * If slicelength < 0, return everything beyond sliceoffset * ---------- */ struct varlena * @@ -206,8 +208,21 @@ detoast_attr_slice(struct varlena *attr, struct varlena *preslice; struct varlena *result; char *attrdata; + int32 slicelimit; int32 attrsize; + if (sliceoffset < 0) + elog(ERROR, "invalid sliceoffset: %d", sliceoffset); + + /* + * Compute slicelimit = offset + length, or -1 if we must fetch all of the + * value. In case of integer overflow, we must fetch all. + */ + if (slicelength < 0) + slicelimit = -1; + else if (pg_add_s32_overflow(sliceoffset, slicelength, &slicelimit)) + slicelength = slicelimit = -1; + if (VARATT_IS_EXTERNAL_ONDISK(attr)) { struct varatt_external toast_pointer; @@ -223,7 +238,7 @@ detoast_attr_slice(struct varlena *attr, * at least the requested part (when a prefix is requested). * Otherwise, just fetch all slices. */ - if (slicelength > 0 && sliceoffset >= 0) + if (slicelimit >= 0) { int32 max_size; @@ -231,7 +246,7 @@ detoast_attr_slice(struct varlena *attr, * Determine maximum amount of compressed data needed for a prefix * of a given length (after decompression). */ - max_size = pglz_maximum_compressed_size(sliceoffset + slicelength, + max_size = pglz_maximum_compressed_size(slicelimit, toast_pointer.va_extsize); /* @@ -270,8 +285,8 @@ detoast_attr_slice(struct varlena *attr, struct varlena *tmp = preslice; /* Decompress enough to encompass the slice and the offset */ - if (slicelength > 0 && sliceoffset >= 0) - preslice = toast_decompress_datum_slice(tmp, slicelength + sliceoffset); + if (slicelimit >= 0) + preslice = toast_decompress_datum_slice(tmp, slicelimit); else preslice = toast_decompress_datum(tmp); @@ -297,8 +312,7 @@ detoast_attr_slice(struct varlena *attr, sliceoffset = 0; slicelength = 0; } - - if (((sliceoffset + slicelength) > attrsize) || slicelength < 0) + else if (slicelength < 0 || slicelimit > attrsize) slicelength = attrsize - sliceoffset; result = (struct varlena *) palloc(slicelength + VARHDRSZ); @@ -410,6 +424,11 @@ toast_fetch_datum_slice(struct varlena *attr, int32 sliceoffset, if (VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer) && slicelength > 0) slicelength = slicelength + sizeof(int32); + /* + * Adjust length request if needed. (Note: our sole caller, + * detoast_attr_slice, protects us against sliceoffset + slicelength + * overflowing.) + */ if (((sliceoffset + slicelength) > attrsize) || slicelength < 0) slicelength = attrsize - sliceoffset; |