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Minor rewordings + formatting fixes.
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man3/hash.3
39
man3/hash.3
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@ -73,46 +73,41 @@ typedef struct {
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.in
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.in
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.PP
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.PP
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The elements of this structure are as follows:
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The elements of this structure are as follows:
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.TP
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.TP 10
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bsize
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.I bsize
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.I Bsize
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defines the hash table bucket size, and is, by default, 256 bytes.
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defines the hash table bucket size, and is, by default, 256 bytes.
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It may be preferable to increase the page size for disk-resident tables
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It may be preferable to increase the page size for disk-resident tables
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and tables with large data items.
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and tables with large data items.
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.TP
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.TP
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ffactor
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.I ffactor
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.I Ffactor
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indicates a desired density within the hash table.
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indicates a desired density within the hash table.
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It is an approximation of the number of keys allowed to accumulate in any
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It is an approximation of the number of keys allowed to accumulate in any
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one bucket, determining when the hash table grows or shrinks.
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one bucket, determining when the hash table grows or shrinks.
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The default value is 8.
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The default value is 8.
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.TP
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.TP
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nelem
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.I nelem
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.I Nelem
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is an estimate of the final size of the hash table.
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is an estimate of the final size of the hash table.
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If not set or set too low, hash tables will expand gracefully as keys
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If not set or set too low, hash tables will expand gracefully as keys
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are entered, although a slight performance degradation may be noticed.
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are entered, although a slight performance degradation may be noticed.
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The default value is 1.
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The default value is 1.
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.TP
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.TP
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cachesize
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.I cachesize
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A suggested maximum size, in bytes, of the memory cache.
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is the suggested maximum size, in bytes, of the memory cache.
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This value is
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This value is
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.B only
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.IR "only advisory" ,
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advisory, and the access method will allocate more memory rather
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and the access method will allocate more memory rather than fail.
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than fail.
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.TP
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.TP
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hash
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.I hash
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.I Hash
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is a user defined hash function.
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is a user defined hash function.
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Since no hash function performs equally well on all possible data, the
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Since no hash function performs equally well on all possible data, the
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user may find that the built-in hash function does poorly on a particular
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user may find that the built-in hash function does poorly on a particular
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data set.
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data set.
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User specified hash functions must take two arguments (a pointer to a byte
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A user-specified hash functions must take two arguments (a pointer to a byte
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string and a length) and return a 32-bit quantity to be used as the hash
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string and a length) and return a 32-bit quantity to be used as the hash
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value.
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value.
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.TP
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.TP
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lorder
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.I lorder
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The byte order for integers in the stored database metadata.
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is the byte order for integers in the stored database metadata.
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The number should represent the order as an integer; for example,
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The number should represent the order as an integer; for example,
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big endian order would be the number 4,321.
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big endian order would be the number 4,321.
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If
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If
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@ -124,7 +119,13 @@ value specified when the tree was created is used.
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If the file already exists (and the
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If the file already exists (and the
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.B O_TRUNC
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.B O_TRUNC
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flag is not specified), the
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flag is not specified), the
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values specified for the parameters bsize, ffactor, lorder and nelem are
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values specified for the parameters
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.IR bsize ,
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.IR ffactor ,
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.IR lorder ,
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and
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.I nelem
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are
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ignored and the values specified when the tree was created are used.
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ignored and the values specified when the tree was created are used.
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.PP
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.PP
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If a hash function is specified,
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If a hash function is specified,
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@ -146,7 +147,7 @@ access method routines may fail and set
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for any of the errors specified for the library routine
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for any of the errors specified for the library routine
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.BR dbopen (3).
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.BR dbopen (3).
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.SH BUGS
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.SH BUGS
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Only big and little endian byte order is supported.
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Only big and little endian byte order are supported.
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.SH "SEE ALSO"
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.SH "SEE ALSO"
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.BR btree (3),
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.BR btree (3),
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.BR dbopen (3),
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.BR dbopen (3),
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