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Rewrite MySQL FIELD function to CASE statement

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PostgreSQL does not provide an equivalent to the MySQL FIELD function.
It is possible to create such a function, although the syntax is
version-dependent (and creates a persistent database object, which so
far has not been done by this plugin).  So use a generic CASE statement.

Fixes: #12

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
This commit is contained in:
Kevin Locke
2017-09-24 14:07:40 -06:00
parent 35e0af4252
commit f896bb1759
1 changed files with 16 additions and 0 deletions
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16
pg4wp/driver_pgsql.php
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@ -281,6 +281,22 @@
$pattern = '/DATE_ADD[ ]*\(([^,]+),([^\)]+)\)/';
$sql = preg_replace( $pattern, '($1 + $2)', $sql);
// Convert MySQL FIELD function to CASE statement
// https://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_field
// Other implementations: https://stackoverflow.com/q/1309624
function pg4wp_rewrite_field($matches)
{
$case = 'CASE ' . trim($matches[1]);
$comparands = explode(',', $matches[2]);
foreach($comparands as $i => $comparand) {
$case .= ' WHEN ' . trim($comparand) . ' THEN ' . ($i + 1);
}
$case .= ' ELSE 0 END';
return $case;
}
$pattern = '/FIELD[ ]*\(([^\),]+),([^\)]+)\)/';
$sql = preg_replace_callback( $pattern, 'pg4wp_rewrite_field', $sql);
$pattern = '/GROUP_CONCAT\(([^()]*(\(((?>[^()]+)|(?-2))*\))?[^()]*)\)/x';
$sql = preg_replace( $pattern, "string_agg($1, ',')", $sql);