Viewing file:  sm_20000509.py (7.19 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
#Steve Meunch's Grouping revelation, with some replication for performance testing. 9 May 2000.
"""
From: "Steve Muench" <smuench@us.oracle.com>
To: <xsl-list@mulberrytech.com>
Subject: Re: grouping (was: if or template?)
Date: Tue, 9 May 2000 01:10:53 -0700 (02:10 MDT)
| ><xsl:key name="tid" use="tracker-id" select="."/>
| >
| ><xsl:for-each
| >select="//tracker-id[generate-id(.)=generate-id(key('tid',.)[1])]">
| >
| >I hope Steve will forgive me for announcing this discovery
| >before he does,
| >I'm quite excited by it because it gives much better performance.
|
| All it does to me is make me scratch my head!
| Steve/Mike, would you give us the idiots view on this please,
| whats happening? *Why* does it provide the unique tracker-id please?
When you're doing grouping, you basically want to select
exactly one of each unique thing.
//tracker-id
would select all tracker-id elements in the document.
Declaring a 'tid' key like:
<xsl:key name="tid" use="tracker-id" select="."/>
The key('tid','tidvalue') function looks up all nodes having
tracker-id = 'tidvalue'. In order to support this lookup,
the processor will be keeping a list in memory like this:
"tid" Key lookup Table
======================
tracker-id Ref to tracker-id elements
value having that value
----------- --------------------------
abc123 node(109),node(344),node(496)
def456 node(15)
hij332 node(89),node(101)
Where the notation node(nnn) means "the node whose node-id is nnn"
as defined by generated-id(). To be concrete, the processor
is likely keeping some kind of Hashtable with the tracker-id
*value* as the hash key, and a node-list as the hash value.
//tracker-id[generate-id(.)=generate-id(key('tid',.)[1])]
selects all tracker-id elements in the document having
a node-id equal to the node-id of the first node in the
"key lookup table's" list of nodes having the current
tracker-id.
Said more simply, it selects the first tracker-id element
for each unique tracker-id value.
Or even more simply, it selects a list of distinct tracker-id values.
Here's an example.
Take the "Task.xml" File below...
[snip xml_source_1]
The stylesheet:
[snip sheet_str_1]
Produces a sorted, grouped list of tasks by owner and
is much faster than the equivalent "scan-my-preceding"
approach...
[snip expected_1]
For testing, here is a slower.xsl stylesheet that
does the same job without using the key() technique:
[snip sheet_str_2]
as you scale up the size of the Task.xml input file, the performance
difference can be dramatic. Try copy/pasting the elements
in the Task.xml above to creates a couple thousand <Task>
elements to give it a spin...
[snip]
"""
#"
from Xml.Xslt import test_harness
sheet_1 = """<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output indent="yes"/>
<xsl:key name="xxx" match="/Tasks/Task/Owner" use="."/>
<xsl:template match="/">
<Tasks>
<xsl:for-each select="/Tasks/Task/Owner[generate-id(.)=generate-id(key('xxx',.))]">
<xsl:sort select="."/>
<Owner name="{.}">
<xsl:for-each select="key('xxx',.)/..">
<xsl:copy-of select="."/>
</xsl:for-each>
</Owner>
</xsl:for-each>
</Tasks>
</xsl:template>
</xsl:stylesheet>
"""
sheet_2 = """<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<!-- Slower.xsl -->
<xsl:output indent="yes"/>
<xsl:template match="/">
<Tasks>
<xsl:for-each
select="/Tasks/Task[not(preceding-sibling::Task/Owner=./Owner)]/Owner">
<xsl:sort select="."/>
<xsl:variable name="owner" select="."/>
<Owner name="{.}">
<xsl:for-each select="/Tasks/Task[Owner = $owner ]">
<xsl:copy-of select="."/>
</xsl:for-each>
</Owner>
</xsl:for-each>
</Tasks>
</xsl:template>
</xsl:stylesheet>
"""
source_1 = """<Tasks>
<Task><Desc>Task1</Desc><Owner>Steve</Owner></Task>
<Task><Desc>Task2</Desc><Owner>Mike</Owner></Task>
<Task><Desc>Task3</Desc><Owner>Dave</Owner></Task>
<Task><Desc>Task4</Desc><Owner>Steve</Owner></Task>
<Task><Desc>Task5</Desc><Owner>Mike</Owner></Task>
<Task><Desc>Task6</Desc><Owner>Mike</Owner></Task>
<Task><Desc>Task7</Desc><Owner>Uche</Owner></Task>
<Task><Desc>Task8</Desc><Owner>Jeremy</Owner></Task>
<Task><Desc>Task9</Desc><Owner>Phil</Owner></Task>
<Task><Desc>Task10</Desc><Owner>Chime</Owner></Task>
<Task><Desc>Task11</Desc><Owner>Glenn</Owner></Task>
<Task><Desc>Task12</Desc><Owner>Uche</Owner></Task>
<Task><Desc>Task13</Desc><Owner>Steve</Owner></Task>
<Task><Desc>Task14</Desc><Owner>Phil</Owner></Task>
<Task><Desc>Task15</Desc><Owner>Dave</Owner></Task>
<Task><Desc>Task16</Desc><Owner>Jeremy</Owner></Task>
<Task><Desc>Task17</Desc><Owner>Steve</Owner></Task>
<Task><Desc>Task18</Desc><Owner>Glenn</Owner></Task>
<Task><Desc>Task19</Desc><Owner>Uche</Owner></Task>
<Task><Desc>Task20</Desc><Owner>Uche</Owner></Task>
</Tasks>
"""
expected_1 = """<?xml version='1.0' encoding='UTF-8'?>
<Tasks>
<Owner name='Chime'>
<Task>
<Desc>Task10</Desc>
<Owner>Chime</Owner>
</Task>
</Owner>
<Owner name='Dave'>
<Task>
<Desc>Task3</Desc>
<Owner>Dave</Owner>
</Task>
<Task>
<Desc>Task15</Desc>
<Owner>Dave</Owner>
</Task>
</Owner>
<Owner name='Glenn'>
<Task>
<Desc>Task11</Desc>
<Owner>Glenn</Owner>
</Task>
<Task>
<Desc>Task18</Desc>
<Owner>Glenn</Owner>
</Task>
</Owner>
<Owner name='Jeremy'>
<Task>
<Desc>Task8</Desc>
<Owner>Jeremy</Owner>
</Task>
<Task>
<Desc>Task16</Desc>
<Owner>Jeremy</Owner>
</Task>
</Owner>
<Owner name='Mike'>
<Task>
<Desc>Task2</Desc>
<Owner>Mike</Owner>
</Task>
<Task>
<Desc>Task5</Desc>
<Owner>Mike</Owner>
</Task>
<Task>
<Desc>Task6</Desc>
<Owner>Mike</Owner>
</Task>
</Owner>
<Owner name='Phil'>
<Task>
<Desc>Task9</Desc>
<Owner>Phil</Owner>
</Task>
<Task>
<Desc>Task14</Desc>
<Owner>Phil</Owner>
</Task>
</Owner>
<Owner name='Steve'>
<Task>
<Desc>Task1</Desc>
<Owner>Steve</Owner>
</Task>
<Task>
<Desc>Task4</Desc>
<Owner>Steve</Owner>
</Task>
<Task>
<Desc>Task13</Desc>
<Owner>Steve</Owner>
</Task>
<Task>
<Desc>Task17</Desc>
<Owner>Steve</Owner>
</Task>
</Owner>
<Owner name='Uche'>
<Task>
<Desc>Task7</Desc>
<Owner>Uche</Owner>
</Task>
<Task>
<Desc>Task12</Desc>
<Owner>Uche</Owner>
</Task>
<Task>
<Desc>Task19</Desc>
<Owner>Uche</Owner>
</Task>
<Task>
<Desc>Task20</Desc>
<Owner>Uche</Owner>
</Task>
</Owner>
</Tasks>"""
def Test(tester):
source = test_harness.FileInfo(string=source_1)
sheet = test_harness.FileInfo(string=sheet_1)
test_harness.XsltTest(tester, source, [sheet], expected_1,
title='test 1')
source = test_harness.FileInfo(string=source_1)
sheet = test_harness.FileInfo(string=sheet_2)
test_harness.XsltTest(tester, source, [sheet], expected_1,
title='test 2')
return
|