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Overview
Comment: | Further documentation updates. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
414ed6da4e175c29d4b27f893a3fd110 |
User & Date: | dan 2012-11-13 20:16:00.788 |
Context
2012-11-14
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18:23 | Improvements to lsmusr.wiki. check-in: e47b5e3ae6 user: dan tags: trunk | |
2012-11-13
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20:16 | Further documentation updates. check-in: 414ed6da4e user: dan tags: trunk | |
18:44 | Add lsmapi.wiki. And the script that generates it from lsm.h - tool/mklsmapi.tcl. check-in: 2377f4f991 user: dan tags: trunk | |
Changes
Changes to tool/mklsmapi.tcl.
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180 181 182 183 184 185 186 | 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 | - + | close $fd puts $document_preamble puts "<h1>LSM API Topics</h1>" puts <ol> puts $document_toc puts </ol> |
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Changes to www/lsmapi.wiki.
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31 32 33 34 35 36 37 | 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 | - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + - + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + | <li><a href="#opening" style=text-decoration:none>Opening and Closing Database Cursors</a> <li><a href="#positioning" style=text-decoration:none>Positioning Database Cursors</a> <li><a href="#extracting" style=text-decoration:none>Extracting Data From Database Cursors</a> <li><a href="#change" style=text-decoration:none>Change these!!</a> </ol> <h1 style=clear:both>All LSM API Functions</h1> |
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Changes to www/lsmusr.wiki.
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69 70 71 72 73 74 75 | 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 | + + + + + + + + + + + + + + + + - - - + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + | it is perhaps more accurate to say that an LSM database is stored on disk in a single database file and a single (optional) log file. <p>If required, it is possible to configure LSM to use external data compression and/or encryption functions to transform data before it is stored in the database file. <p>Many database systems that support range queries, including <a href=http://www.sqlite.org>SQLite 3</a>, Berkeley DB and Kyoto Cabinet, are based on a <a href="http://en.wikipedia.org/wiki/B-tree">b-tree data structure</a> or variant thereof. A b-tree structure minimizes the number of disk sectors that must be read from disk when searching the database for a specific key. However, b-tree implementations usually suffer from poor write localization - updating the contents of a b-tree often involves modifying the contents of nodes scattered throughout the database file. If the database is stored on a spinning disk (HDD), then the disk heads must be moved before writing non-contiguous sector, which is extremely slow. If the database is stored on solid state storage (SDD) a similar phenomena is encountered due to the large erase-block sizes. In general, writing to a series of contiguous disk sectors is orders of magnitude faster than updating to the same number of disk sectors scattered randomly throughout a large file. Additionally, b-tree structures are prone to fragmentation, reducing the speed of range queries. |
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