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accesslib: build_context_path() - better UPDATE SQL

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A bit of cleanup on the SQL we use for updates. Unfortunately, MySQL
uses non-SQL-standard syntax for updates reading or updating multiple
tables. After much testing across Pg and MySQL, I boiled it down to
the minimal differences -- but we still have different SQL.

The timings for this on a large reference install, calling
build_context_path(true):

 - MySQL incompatible 1s
 - Petr's fixes 60s -- DB complains of too many writes
 - This commit 24s  -- DB complains of too many writes

Also - fixed a remaining problem with $emptyclause

Affects MDL-11347
This commit is contained in:
martinlanghoff
2007-09-20 01:03:35 +00:00
parent 92b34bdd6c
commit d20559f3e4
1 changed files with 17 additions and 27 deletions
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lib/accesslib.php
+17 -27
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@@ -4445,29 +4445,23 @@ function build_context_path($force=false) {
$ctxemptyclause = " AND (ctx.depth IS NULL
OR ctx.depth=0) ";
$emptyclause = " AND (context.depth IS NULL
OR context.depth=0) ";
$emptyclause = " AND ({$CFG->prefix}context.depth IS NULL
OR {$CFG->prefix}context.depth=0) ";
if ($force) {
$ctxemptyclause = $emptyclause = '';
}
// TODO: following could be improved with WHERE + $emptyclause, but there should be a better way
$upathsql = "UPDATE {$CFG->prefix}context
SET path = COALESCE((SELECT ct.path FROM {$CFG->prefix}$temptable ct WHERE {$CFG->prefix}context.id=ct.id), {$CFG->prefix}context.path)";
$udepthsql = "UPDATE {$CFG->prefix}context
SET depth = COALESCE((SELECT ct.depth FROM {$CFG->prefix}$temptable ct WHERE {$CFG->prefix}context.id=ct.id), {$CFG->prefix}context.depth)";
/*
* TODO: following code complains: Can't reopen table: 'ct' when using temporary teables, why?
$upathsql = "UPDATE {$CFG->prefix}context
SET path = (SELECT ct.path FROM {$CFG->prefix}$temptable ct WHERE {$CFG->prefix}context.id=ct.id)
WHERE id IN (SELECT ctx.id FROM {$CFG->prefix}$temptable ctx)";
$udepthsql = "UPDATE {$CFG->prefix}context
SET depth = (SELECT ct.depth FROM {$CFG->prefix}$temptable ct WHERE {$CFG->prefix}context.id=ct.id)
WHERE id IN (SELECT ct.id FROM {$CFG->prefix}$temptable ct)";
*/
$updatesql = "UPDATE {$CFG->prefix}context
SET path = ct.path,
depth = ct.depth
FROM {$CFG->prefix}$temptable ct
WHERE ct.id={$CFG->prefix}context.id";
if ($CFG->dbtype==='mysql') {
$updatesql = "UPDATE {$CFG->prefix}context, {$CFG->prefix}$temptable
SET {$CFG->prefix}context.path = {$CFG->prefix}$temptable.path,
{$CFG->prefix}context.depth = {$CFG->prefix}$temptable.depth
WHERE {$CFG->prefix}$temptable.id={$CFG->prefix}context.id";
}
$udelsql = "TRUNCATE TABLE {$CFG->prefix}$temptable";
// Top level categories
@@ -4499,8 +4493,7 @@ function build_context_path($force=false) {
execute_sql($sql, $force);
}
execute_sql($upathsql, $force);
execute_sql($udepthsql, $force);
execute_sql($updatesql, $force);
execute_sql($udelsql, $force);
// Courses -- except sitecourse
@@ -4515,8 +4508,7 @@ function build_context_path($force=false) {
$ctxemptyclause";
execute_sql($sql, $force);
execute_sql($upathsql, $force);
execute_sql($udepthsql, $force);
execute_sql($updatesql, $force);
execute_sql($udelsql, $force);
// Module instances
@@ -4530,8 +4522,7 @@ function build_context_path($force=false) {
$ctxemptyclause";
execute_sql($sql, $force);
execute_sql($upathsql, $force);
execute_sql($udepthsql, $force);
execute_sql($updatesql, $force);
execute_sql($udelsql, $force);
// Blocks - non-pinned course-view only
@@ -4546,8 +4537,7 @@ function build_context_path($force=false) {
$ctxemptyclause";
execute_sql($sql, $force);
execute_sql($upathsql, $force);
execute_sql($udepthsql, $force);
execute_sql($updatesql, $force);
execute_sql($udelsql, $force);
// Blocks - others