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Overview
| Comment: | Add a "todo" note to fix the schema file-format range. Also fix another todo in fileformat.html. |
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| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
14e677d1dc45ad0056ebbe82b4db482d |
| User & Date: | dan 2009-05-26 15:13:30.000 |
Context
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2009-05-26
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| 23:13 | Improve the internal links from text to glossary definitions in fileformat.html. Also fix a bunch of issues reported by John Machin on the mailing list. (check-in: c5aa49ff35 user: dan tags: trunk) | |
| 15:13 | Add a "todo" note to fix the schema file-format range. Also fix another todo in fileformat.html. (check-in: 14e677d1dc user: dan tags: trunk) | |
| 04:32 | Modify some requirements in fileformat.html to make them more testable. (check-in: 9a9955c381 user: dan tags: trunk) | |
Changes
Changes to pages/fileformat.in.
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<li>If the database is an auto-vacuum database, a flag indicating
whether or not the database is in incremental vacuum mode or not.
<li>The default page cache size in pages to use with the database (an
integer field).
</ol>
</ul>
| | > > | | > > | | 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 |
<li>If the database is an auto-vacuum database, a flag indicating
whether or not the database is in incremental vacuum mode or not.
<li>The default page cache size in pages to use with the database (an
integer field).
</ol>
</ul>
<p>
Of the six database properties enumerated above, the values taken by the
initial three dramatically affect the structure of the database image. Any
software system that handles SQLite database images will need to understand
and interpret them. Properties 4 to 6 may be considered advisory. Although
properties 5 and 6 modify the operation of the SQLite library in
well-defined manners, an alternative SQLite database client is free to
interpret them differently, or not interpret them at all.
<p class=todo>
The concept of a logical database and its contents should be defined
properly in some requirements document so that it can be referenced from
here and other places. The definition will be something like the list of
bullet points above.
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<li> Implicit default (non-NULL) values at the end of table
records (see section <cite>table_btree_content</cite>).
<li> Descending indexes (see section
<cite>index_btree_compare_func</cite>) and Boolean values
in database records (see section <cite>record_format</cite>,
serial types 8 and 9).
</ol>
<td>H30120
[Tr]<td>48..51 <td>4<td>
Default pager cache size. This field is used by SQLite to store
the recommended pager cache size to use for the database.
<td>H30130
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<li> Implicit default (non-NULL) values at the end of table
records (see section <cite>table_btree_content</cite>).
<li> Descending indexes (see section
<cite>index_btree_compare_func</cite>) and Boolean values
in database records (see section <cite>record_format</cite>,
serial types 8 and 9).
</ol>
<p class=todo>
Turns out SQLite can be tricked into violating this. If you delete
all tables from a database and then VACUUM the database, the
schema layer file-format field somehow gets set to 0.
<td>H30120
[Tr]<td>48..51 <td>4<td>
Default pager cache size. This field is used by SQLite to store
the recommended pager cache size to use for the database.
<td>H30130
|
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[fileformat_import_requirement2 H30210]
[fileformat_import_requirement2 H30220]
[h3 "The Schema Table" schema_table]
<p>
Apart from being the page that contains the file-header, page 1 of
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[fileformat_import_requirement2 H30210]
[fileformat_import_requirement2 H30220]
[h3 "The Schema Table" schema_table]
<p>
Apart from being the page that contains the file-header, page 1 of
a database image is special because it is the root page of the
B-Tree structure that contains the schema table data. From the SQL
level, the schema table is accessible via the name "sqlite_master".
<p>
The exact format of the B-Tree structure and the meaning of the term
"root page" is discussed in section <cite>btree_structures</cite>.
For now, it is sufficient to know that the B-Tree structure is a
data structure that stores a set of records. Each record is an
|
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