Transaction Management - Revision history

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2023-12-01T16:36:49Z

Text replacement - "<syntaxhighlight lang="xquery">" to "<pre lang='xquery'>"

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2023-12-01T16:33:16Z

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2023-10-26T10:15:28Z

XQuery

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2023-10-26T10:10:42Z

XQuery

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2023-07-25T12:37:12Z

Annotations

CG at 08:19, 21 July 2022

2022-07-21T08:19:06Z

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2022-07-20T11:59:18Z

XQuery

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2022-07-20T11:57:12Z

XQuery

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2022-07-20T11:55:33Z

XQuery

CG at 11:55, 20 July 2022

2022-07-20T11:55:08Z

@@ Line 111: / Line 111: @@
 In the following module, lock annotations are used to prevent concurrent write operations on the same file:
-<syntaxhighlight lang="xquery">
+<pre lang='xquery'>
 module namespace config = 'config';
@@ Line 133: / Line 133: @@
 Locks can also be declared via pragmas:
-<syntaxhighlight lang="xquery">
+<pre lang='xquery'>
 update:output((# basex:lock CONFIG #) {
    file:write('config.xml', <config/>)
@@ Line 145: / Line 145: @@
 Locks for the functions of a module can also be assigned via option declarations:
-<syntaxhighlight lang="xquery">
+<pre lang='xquery'>
 declare option basex:lock 'CONFIG';

@@ Line 121: / Line 121: @@
    file:write-text('config.txt', $data)
 };
-</syntaxhighlight>
+</pre>
 Some explanations:
@@ Line 137: / Line 137: @@
    file:write('config.xml', <config/>)
 })
-</syntaxhighlight>
+</pre>
 The write locks is enforced via the {{Code|Update|update:output}}.
@@ Line 149: / Line 149: @@
 update:output(file:write('config.xml', <config/>))
-</syntaxhighlight>
+</pre>
 Once again, a write lock is enforced.

@@ Line 41: / Line 41: @@
 ===XQuery===
-With BaseX 10, the [[BaseX 10#Compilation|lock detection has been fundamentally improved]], by splitting compilation into multiple steps.
+Since BaseX 10, the [[BaseX 10#Compilation|lock detection has been fundamentally improved]], by splitting compilation into multiple steps.
 Local locks can be applied if it is possible after compile time to associate all database operations with static databases names:

@@ Line 41: / Line 41: @@
 ===XQuery===
-With {{Announce|Version 10}}, the [[BaseX 10#Compilation|lock detection has been fundamentally improved]], by splitting compilation into multiple steps.
+With BaseX 10, the [[BaseX 10#Compilation|lock detection has been fundamentally improved]], by splitting compilation into multiple steps.
 Local locks can be applied if it is possible after compile time to associate all database operations with static databases names:

@@ Line 125: / Line 125: @@
 Some explanations:
-* If a query calls the <code>config:read</code> function, a read lock will be acquired for the user-defined {{Code|CONFIG}} lock string before query evaluation.
+* If a query calls a reading <code>basex:lock</code> function, a read lock will be acquired for the user-defined {{Code|CONFIG}} lock string before query evaluation.
-* If <code>config:write</code> is called by a query, a write lock will be applied.
+* If an updating <code>basex:lock</code> is called by a query, a write lock will be applied.
-* If another query calls <code>config:write</code>, it will be queued until the first query is evaluated.
+* If another query calls a <code>basex:lock</code> function, it will be queued until the first query is evaluated.
 ==Pragmas==

@@ Line 46: / Line 46: @@
 {| class="wikitable"
-|-
+|- valign="top"
 ! Query
 ! Description
-|-
+|- valign="top"
 | <code>//item</code>
 | Read lock of the currently opened database
-|-
+|- valign="top"
 | <code>doc('factbook')</code>
 | Read lock of the {{Code|factbook}} database
-|-
+|- valign="top"
 | <code>collection('documents/path/to/docs')</code>
 | Read lock of the {{Code|documents}} database
-|-
+|- valign="top"
 | <code>delete nodes db:get('test')//*[@type = 'misc']</code>
 | Write lock of the {{Code|test}} database
-|-
+|- valign="top"
 | <code>declare variables $db external;<br/>db:get($db)</code>
 | Read lock of the database externally bound to {{Code|$db}}.
-|-
+|- valign="top"
 | <code>for $db in ('db1', 'db2')<br/>return db:get($db)</code>
 | Read lock of {{Code|db1}} and {{Code|db2}}, as the query is [[XQuery Optimizations#Loop Unrolling|unrolled at compile time]].
-|-
+|- valign="top"
 | <code>let $db := 'test'<br/>return insert nodes <test/> into db:get($db)</code>
 | Read lock of {{Code|test}}, as the [[XQuery Optimizations#Variable_Inlining|variable is inlined]] at compile time.
-|-
+|- valign="top"
 | <code>sum(1 to 100)</code>
 | No lock required
-|-
+|- valign="top"
 | <code>declare variable $SIMULATE := true();<br/>if($SIMULATE) then <doc/> else db:get('doc')</code>
 | No lock required, as the query is simplified to {{Code|<doc/>}} at compile time.
@@ Line 81: / Line 81: @@
 {| class="wikitable"
-|-
+|- valign="top"
 ! Query
 ! Description
-|-
+|- valign="top"
 | <code>db:get(doc('test')/reference/text())</code>
 | The name of the database to be opened will only be known at evaluation time.
-|-
+|- valign="top"
 | <code>(1 to 100) ! db:get(concat('db', .))</code>
 | The {{Option|UNROLLLIMIT}} can be increased to generate 100 {{Code|db:get}} function calls and corresponding locks.

@@ Line 43: / Line 43: @@
 With {{Announce|Version 10}}, [[BaseX 10#Compilation|lock detection was improved]] by splitting compilation into multiple steps.
-Local locks can be applied if it is possible at compile time to associate names of databases with database operations:
+Local locks can be applied if it is possible after compile time to associate all database operations with static databases names:
 {| class="wikitable"
@@ Line 50: / Line 50: @@
 ! Description
 |-
-| {{Code|//item}}
+| <code>//item</code>
 | Read lock of the currently opened database
 |-
-| {{Code|doc('factbook')}}
+| <code>doc('factbook')</code>
 | Read lock of the {{Code|factbook}} database
 |-
-| {{Code|collection('documents/path/to/docs')}}
+| <code>collection('documents/path/to/docs')</code>
 | Read lock of the {{Code|documents}} database
 |-
-| {{Code|delete nodes db:get('test')//*[string-length(local-name(.)) > 5]}}
+| <code>delete nodes db:get('test')//*[@type = 'misc']</code>
 | Write lock of the {{Code|test}} database
 |-
-| {{Code|fn:sum(1 to 100)}}
+| <code>declare variables $db external;<br/>db:get($db)</code>
-| ''no lock''
+| Read lock of the database externally bound to {{Code|$db}}.
 |-
-| {{Code|for $db in ('db1', 'db2') return db:get($db)}}
+| <code>for $db in ('db1', 'db2')<br/>return db:get($db)</code>
 | Read lock of {{Code|db1}} and {{Code|db2}}, as query is [[XQuery Optimization#Loop Unrolling|unrolled at compile time]].
 |-
-| {{Code|declare variables $db external; db:get($db)}}
+| <code>let $db := 'test'<br/>return insert nodes <test/> into db:get($db)</code>
-| Read lock of the database externally bound to {{Code|$db}}.
+| Read lock of {{Code|test}}, as the [[XQuery Optimizations#Variable_Inlining|variable is inlined]] at compile time.
 |}
-A global lock will be assigned if the name of the database is not a static string:
+A global lock will be assigned if the static detection fails:
-* {{Code|doc(doc('test')/reference/text())}}
+The functions {{Code|fn:doc}} and {{Code|fn:collection}} can be used for both accessing databases resources and fetching resources at the specified URI (see [[Databases#Access Resources|Access Resources]] for more details). There are two ways to reduce the number of locks:
-The functions {{Code|fn:doc}} and {{Code|fn:collection}} can also be used to address that are not stored in a database. However, this may lead to unwanted locks, and you have two options to reduce the number of locks: No database lookups will take place if {{Option|WITHDB}} option is disabled, or if {{Function|Fetch|fetch:doc}} is used instead of {{Code|fn:doc}}.
+# Turn off the {{Option|WITHDB}} option to prevent the functions from accessing databases; or
-You can consult the query info output (which you find in the [[GUI#Visualizations|Info View]] of the GUI or which you can turn on by setting {{Option|QUERYINFO}} to {{Code|true}}) to find out which databases have been locked by a query.
+You can consult the query info output (via the [[GUI#Visualizations|Info View]] of the GUI, via {{Code|-V}} on [[Command-Line]] or via turning on the {{Option|QUERYINFO}} option) to find out which databases are locked by a query, and if local locks or a global lock is applied.
 =XQuery Locks=
-By default, access to external resources (files on hard disk, HTTP requests, ...) is not controlled by the transaction monitor of BaseX. Custom locks can be assigned via annotations, pragmas or options:
+By default, access to external resources (files on hard disk, HTTP requests, …) is not controlled by the transaction monitor of BaseX. Custom locks can be assigned via annotations, pragmas or options:
 * A lock string may consist of a single key or multiple keys separated with commas.