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Annotation of 42BSD/ingres/doc/quel/modify.nr, revision 1.1

1.1     ! root        1: .th MODIFY QUEL 2/23/79
        !             2: .sh NAME
        !             3: modify \- convert the storage structure of a relation
        !             4: .sh SYNOPSIS
        !             5: .in +5
        !             6: .ti -5
        !             7: .bd modify 
        !             8: relname 
        !             9: .bd to 
        !            10: storage-structure
        !            11: [
        !            12: .bd on 
        !            13: key1 [ :
        !            14: .it sortorder
        !            15: ] [ { , key2 [ :
        !            16: .it sortorder
        !            17: ] } ] ] 
        !            18: [
        !            19: .bd where 
        !            20: [
        !            21: .bd "fillfactor =" 
        !            22: .it n
        !            23: ] [
        !            24: .bd ", minpages =" 
        !            25: .it n
        !            26: ] [
        !            27: .bd ", maxpages =" 
        !            28: .it n
        !            29: ] ]
        !            30: .i0
        !            31: .sh DESCRIPTION
        !            32: .it Relname 
        !            33: is modified to the specified storage structure.
        !            34: Only the owner of a relation can modify that relation.
        !            35: This command is used to increase performance when using large
        !            36: or frequently referenced relations.
        !            37: The storage structures are specified as follows:
        !            38: .s3
        !            39: .if n .in +10
        !            40: .if t .in +1i
        !            41: .de xx
        !            42: .if n .ti -5
        !            43: .if t .ti -0.5i
        !            44: ..
        !            45: .xx
        !            46: isam \- indexed sequential storage structure
        !            47: .xx
        !            48: cisam \- compressed isam
        !            49: .xx
        !            50: hash \- random hah storage structure
        !            51: .xx
        !            52: chash \- compressed hash
        !            53: .xx
        !            54: heap \- unkeyed and unstructured
        !            55: .xx
        !            56: cheap \- compressed heap
        !            57: .xx
        !            58: heapsort \- heap with tuples sorted and duplicates removed
        !            59: .xx
        !            60: cheapsort \- compressed heapsort
        !            61: .xx
        !            62: truncated \- heap with all tuples deleted
        !            63: .s3
        !            64: .i0
        !            65: The paper ``Creating and Maintaining a Database in \*(II''
        !            66: (ERL Memo M77\-71)
        !            67: discusses how to select storage structures
        !            68: based on how the relation is used.
        !            69: .s3
        !            70: The current compression algorithm only suppresses trailing
        !            71: blanks in character fields.
        !            72: A more effective compression scheme may be possible,
        !            73: but tradeoffs between that and a larger and slower
        !            74: compression algorithm are not clear.
        !            75: .s3
        !            76: If the 
        !            77: .it on
        !            78: phrase is omitted when modifying to isam, cisam, hash or chash,
        !            79: the relation will automatically be keyed on the first domain.
        !            80: When modifying to heap or cheap the 
        !            81: .it on
        !            82: phrase must be omitted.
        !            83: When modifying to heapsort or cheapsort the 
        !            84: .it on
        !            85: phrase is optional.
        !            86: .s3
        !            87: When a relation is being sorted (isam, cisam, heapsort and cheapsort),
        !            88: the primary sort keys will be those specified in the 
        !            89: .it on
        !            90: phrase (if any).
        !            91: The first key after the 
        !            92: .it on
        !            93: phrase will be the most significant sort key
        !            94: and each successive key specified will be the next most significant
        !            95: sort key.
        !            96: Any domains not specified in the 
        !            97: .it on
        !            98: phrase will be used as least
        !            99: significant sort keys in domain number sequence.
        !           100: .s3
        !           101: When a relation is modified to heapsort or cheapsort,
        !           102: the 
        !           103: .it sortorder
        !           104: can be specified to be 
        !           105: .bd ascending 
        !           106: or
        !           107: .bd descending.
        !           108: The default is always 
        !           109: .bd ascending.
        !           110: Each key given in the
        !           111: .it on
        !           112: phrase can be optionally modified
        !           113: to be:
        !           114: .s1
        !           115: .if n .ti +5
        !           116: .if t .ti +0.5i
        !           117: key:descending
        !           118: .s1
        !           119: which will cause that key to be sorted in descending order.
        !           120: For completeness, 
        !           121: .bd ascending
        !           122: can be specified after the colon (`:'),
        !           123: although this is unnecessary since
        !           124: it is the default.
        !           125: .bd Descending
        !           126: can be abbreviated by a single `\c
        !           127: .bd d\c
        !           128: \&' and, correspondingly,
        !           129: .bd ascending 
        !           130: can be abreviated by a single `\c
        !           131: .bd a\c
        !           132: \&'.
        !           133: .s3
        !           134: .it Fillfactor 
        !           135: specifies the percentage
        !           136: (from 1 to 100)
        !           137: of each primary data page that should be filled
        !           138: with tuples, under ideal conditions.
        !           139: .it Fillfactor
        !           140: may be used with isam, cisam, hash and chash.
        !           141: Care should be taken when using large fillfactors since a non-uniform
        !           142: distribution of key values could cause overflow pages to be created,
        !           143: and thus degrade access performance for the relation.
        !           144: .s3
        !           145: .it Minpages 
        !           146: specifies the minimum number of primary pages a hash or chash
        !           147: relation must have.
        !           148: .it Maxpages
        !           149: specifies the maximum number of primary pages
        !           150: a hash or chash relation may have.
        !           151: .it Minpages 
        !           152: and 
        !           153: .it maxpages 
        !           154: must be at least one.
        !           155: If both 
        !           156: .bd minpages 
        !           157: and 
        !           158: .bd maxpages 
        !           159: are specified in a modify,
        !           160: .bd minpages 
        !           161: cannot exceed 
        !           162: .bd maxpages.
        !           163: .sp
        !           164: Default values for 
        !           165: .bd fillfactor\c
        !           166: , 
        !           167: .bd minpages\c
        !           168: , and 
        !           169: .bd maxpages 
        !           170: are as follows:
        !           171: .if n .ta 5 12 25 35
        !           172: .if t .ta 0.5i 1i 3i 4.5i
        !           173: .nf
        !           174: .ul
        !           175: .s1
        !           176:                FILLFACTOR      MINPAGES        MAXPAGES
        !           177: .s2
        !           178:        hash    50      10      no limit
        !           179:        chash   75      1       no limit
        !           180:        isam    80      NA      NA
        !           181:        cisam   100     NA      NA
        !           182: .fi
        !           183: .dt
        !           184: .sh EXAMPLES
        !           185: .nf
        !           186: /* modify the emp relation to an indexed
        !           187:         sequential storage structure with
        !           188:         "name" as the keyed domain */
        !           189: .s1
        !           190: modify emp to isam on name
        !           191: .s1
        !           192: /* if "name" is the first domain of the emp relation,
        !           193:         the same result can be achieved by */
        !           194: .s1
        !           195: modify emp to isam
        !           196: .s1
        !           197: /* do the same modify but request a 60% occupancy
        !           198:         on all primary pages */
        !           199: .s1
        !           200: modify emp to isam on name where fillfactor = 60
        !           201: 
        !           202: /* modify the supply relation to compressed hash
        !           203:         storage structure with "num" and "quan"
        !           204:         as keyed domains */
        !           205: .s1
        !           206: modify supply to chash on num, quan
        !           207: .s1
        !           208: /* now the same modify but also request 75% occupancy
        !           209:         on all primary, a minimum of 7 primary pages
        !           210:         pages and a maximum of 43 primary pages */
        !           211: .s1
        !           212: modify supply to chash on num, quan
        !           213:         where fillfactor = 75, minpages = 7,
        !           214:         maxpages = 43
        !           215: .s1
        !           216: /* again the same modify but only request a minimum
        !           217:         of 16 primary pages */
        !           218: .s1
        !           219: modify supply to chash on num, quan
        !           220:         where minpages = 16
        !           221: .s1
        !           222: /* modify parts to a heap storage structure */
        !           223: .s1
        !           224: modify parts to heap
        !           225: .s1
        !           226: /* modify parts to a heap again, but have tuples
        !           227:         sorted on "pnum" domain and have any duplicate
        !           228:         tuples removed */
        !           229: .s1
        !           230: modify parts to heapsort on pnum
        !           231: .s1
        !           232: /* modify employee in ascending order by manager,
        !           233:         descending order by salary and have any
        !           234:         duplicate tuples removed */
        !           235: .s1
        !           236: modify employee to heapsort on manager, salary:descending
        !           237: .fi
        !           238: .sh "SEE ALSO"
        !           239: sysmod(unix)

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