Difference between revisions of "Storage Layout"
Jump to navigation
Jump to search
Meta Data, Name/Path/Doc Indexes:
Node Table:
Texts:
Value Indexes:
Full-Text Fuzzy Index:
Full-Text Trie Index:
Line 7: | Line 7: | ||
! Type | ! Type | ||
! Description | ! Description | ||
− | ! Example | + | ! Example (native → hex integers) |
|- | |- | ||
− | + | | {{Type|Num}} | |
− | + | | Compressed integer (1-5 bytes), specified in [https://github.com/BaseXdb/basex/blob/master/src/main/java/org/basex/util/Num.java Num.java] | |
− | | | + | | {{Mono|15}} → {{Mono|0F}}; {{Mono|511}} → {{Mono|41 FF}}<br/> |
+ | |- | ||
+ | | {{Type|Token}} | ||
+ | | Length ({{Type|Num}}) and bytes of UTF8 byte representation | ||
+ | | {{Mono|Hello}} → {{Mono|05 48 65 6c 6c 6f}} | ||
+ | |- | ||
+ | | {{Type|Double}} | ||
+ | | Number, stored as token | ||
+ | | {{Mono|123}} → {{Mono|03 31 32 33}} | ||
+ | |- | ||
+ | | {{Type|Boolean}} | ||
+ | | Boolean (1 byte, <code>00</code> or <code>01</code>) | ||
+ | | {{Mono|true}} → {{Mono|01}} | ||
+ | |- | ||
+ | | {{Type|Nums}}, {{Type|Tokens}}, {{Type|Doubles}} | ||
+ | | Arrays of values, introduced with the number of entries | ||
+ | | {{Mono|1,2}} → {{Mono|02 01 31 01 32}} | ||
+ | |- | ||
+ | | {{Type|TokenSet}} | ||
+ | | Key array ({{Type|Tokens}}), next/bucket/size arrays (3x {{Type|Nums}}) | ||
+ | | | ||
|} | |} | ||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
=Database Files= | =Database Files= |
Revision as of 19:41, 26 October 2011
The following data types are used for specifying the storage layout:
Contents
Data Types
Type | Description | Example (native → hex integers) |
---|---|---|
Num
|
Compressed integer (1-5 bytes), specified in Num.java | 15 → 0F ; 511 → 41 FF |
Token
|
Length (Num ) and bytes of UTF8 byte representation
|
Hello → 05 48 65 6c 6c 6f
|
Double
|
Number, stored as token | 123 → 03 31 32 33
|
Boolean
|
Boolean (1 byte, 00 or 01 )
|
true → 01
|
Nums , Tokens , Doubles
|
Arrays of values, introduced with the number of entries | 1,2 → 02 01 31 01 32
|
TokenSet
|
Key array (Tokens ), next/bucket/size arrays (3x Nums )
|
Database Files
The following tables present the layout of BaseX database files. All files are suffixed with .basex
.
Meta Data, Name/Path/Doc Indexes: inf
Description | Format | Method |
---|---|---|
1. Meta Data | 1. Key/value pairs (Token /Token ):• PERM → Number of users (Num ), and name/password/permission values for each user (Token /Token /Num )2. Empty key as finalizer |
DiskData() MetaData() Users() |
2. Main memory indexes | 1. Key/value pairs (Token /Token ):• TAGS → Tag Index• ATTS → Attribute Name Index• PATH → Path Index• NS → Namespaces• DOCS → Document Index2. Empty key as finalizer |
DiskData() |
2 a) Name Index Tag/attribute names |
1. Token set, storing all names (TokenSet )2. One StatsKey instance per entry: 2.1. Content kind ( Num ):2.1.1. Number: min/max ( Doubles )2.1.2. Category: number of entries ( Num ), entries (Tokens )2.2. Number of entries ( Num )2.3. Leaf flag ( Boolean )2.4. Maximum text length ( Double ; legacy, could be Num )
|
Names() TokenSet.read() StatsKey() |
2 b) Path Index | 1. Flag for path definition (Boolean , always true ; legacy)2. PathNode: 2.1. Name reference ( Num )2.2. Node kind ( Num )2.3. Number of occurrences ( Num )2.4. Number of children ( Num )2.5. Double ; legacy, can be reused or discarded2.6. Recursive generation of child nodes (→ 2) |
PathSummary() PathNode() |
2 c) Namespaces | 1. Token set, storing prefixes (TokenSet )2. Token set, storing URIs ( TokenSet )3. NSNode: 3.1. pre value ( Num )3.2. References to prefix/URI pairs ( Nums )3.3. Number of children ( Num )3.4. Recursive generation of child nodes (→ 3) |
Namespaces() NSNode() |
2 d) Document Index | Array of integers, representing the distances between all document pre values (Nums )
|
DocIndex() |
Node Table: tbl
, tbli
tbl
: Main database table, stored in blocks.tbli
: Database directory, organizing the database blocks.
Texts: txt
, atv
txt
: Heap file for text values (document names, string values of texts, comments and processing instructions)atv
: Heap file for attribute values.
Value Indexes: txtl
, txtr
, atvl
, atvr
Text Index:
txtl
: Heap file with ID lists.txtr
: Index file with references to ID lists.
The Attribute Index is contained in the files atvl
and atvr
; it uses the same layout.
Full-Text Fuzzy Index: ftxx
, ftxy
, ftxz
...will soon be reimplemented.
Full-Text Trie Index: ftxa
, ftxb
, ftxc
...will soon be dismissed.