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Overview
Comment: | Update the btree file format description in btreeInt.h. (CVS 4063) |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
1ac160d3dc0f8723a1e2007cf45351dd |
User & Date: | drh 2007-06-15 12:06:59.000 |
Context
2007-06-15
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12:16 | Documentation updates in preparation for 3.4.0. (CVS 4064) (check-in: 5232fd29d0 user: drh tags: trunk) | |
12:06 | Update the btree file format description in btreeInt.h. (CVS 4063) (check-in: 1ac160d3dc user: drh tags: trunk) | |
2007-06-14
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20:57 | The C-api reference documentation is now generated directly from comments in the sqlite3.h header file. (CVS 4062) (check-in: d93c41e9a9 user: drh tags: trunk) | |
Changes
Changes to src/btreeInt.h.
1 2 3 4 5 6 7 8 9 10 11 | /* ** 2004 April 6 ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ************************************************************************* | | | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | /* ** 2004 April 6 ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ************************************************************************* ** $Id: btreeInt.h,v 1.5 2007/06/15 12:06:59 drh Exp $ ** ** This file implements a external (disk-based) database using BTrees. ** For a detailed discussion of BTrees, refer to ** ** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3: ** "Sorting And Searching", pages 473-480. Addison-Wesley ** Publishing Company, Reading, Massachusetts. |
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69 70 71 72 73 74 75 | ** 28 4 Reserved for future use ** 32 4 First freelist page ** 36 4 Number of freelist pages in the file ** 40 60 15 4-byte meta values passed to higher layers ** ** All of the integer values are big-endian (most significant byte first). ** | | < | | < | | 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 | ** 28 4 Reserved for future use ** 32 4 First freelist page ** 36 4 Number of freelist pages in the file ** 40 60 15 4-byte meta values passed to higher layers ** ** All of the integer values are big-endian (most significant byte first). ** ** The file change counter is incremented when the database is changed ** This counter allows other processes to know when the file has changed ** and thus when they need to flush their cache. ** ** The max embedded payload fraction is the amount of the total usable ** space in a page that can be consumed by a single cell for standard ** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default ** is to limit the maximum cell size so that at least 4 cells will fit ** on one page. Thus the default max embedded payload fraction is 64. ** ** If the payload for a cell is larger than the max payload, then extra ** payload is spilled to overflow pages. Once an overflow page is allocated, ** as many bytes as possible are moved into the overflow pages without letting ** the cell size drop below the min embedded payload fraction. ** ** The min leaf payload fraction is like the min embedded payload fraction ** except that it applies to leaf nodes in a LEAFDATA tree. The maximum ** payload fraction for a LEAFDATA tree is always 100% (or 255) and it ** not specified in the header. ** ** Each btree pages is divided into three sections: The header, the ** cell pointer array, and the cell content area. Page 1 also has a 100-byte ** file header that occurs before the page header. ** ** |----------------| ** | file header | 100 bytes. Page 1 only. ** |----------------| ** | page header | 8 bytes for leaves. 12 bytes for interior nodes ** |----------------| |
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192 193 194 195 196 197 198 | ** as 1 byte of data. ** ** SIZE DESCRIPTION ** 4 Page number of next overflow page ** * Data ** ** Freelist pages come in two subtypes: trunk pages and leaf pages. The | | | 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 | ** as 1 byte of data. ** ** SIZE DESCRIPTION ** 4 Page number of next overflow page ** * Data ** ** Freelist pages come in two subtypes: trunk pages and leaf pages. The ** file header points to the first in a linked list of trunk page. Each trunk ** page points to multiple leaf pages. The content of a leaf page is ** unspecified. A trunk page looks like this: ** ** SIZE DESCRIPTION ** 4 Page number of next trunk page ** 4 Number of leaf pointers on this page ** * zero or more pages numbers of leaves |
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