SQLPlatform: Introduce buildComparison()

Builds a condition comparing multiple values, for use with indexes
that cover multiple fields, common when e.g. paging through results
or doing batch operations. Can also be to generate a simple comparison
without writing raw SQL (see T210206).

Update a few manually constructed conditions to use this method.
There are more maintenance scripts and API classes that use the
same patterns, but this is a start.

As you can see by the code I'm replacing, there are many ways to do
this. I picked the one used by maintenance/TableCleanup.php, since
I found it the easiest to understand.

Change-Id: Ic368a87fb5ce4c13608b03206cd68518ec9732d4

1 files changed, 4 insertions, 12 deletions

diff --git a/maintenance/TableCleanup.php b/maintenance/TableCleanup.php
index 53bc915c9e14..779f7c9f84af 100644
--- a/maintenance/TableCleanup.php
+++ b/maintenance/TableCleanup.php
@@ -148,20 +148,12 @@ class TableCleanup extends Maintenance {
 			}
 
 			// Update the conditions to select the next batch.
-			// Construct a condition string by starting with the least significant part
-			// of the index, and adding more significant parts progressively to the left
-			// of the string.
-			$nextCond = '';
-			foreach ( array_reverse( $index ) as $field ) {
+			$conds = [];
+			foreach ( $index as $field ) {
 				// @phan-suppress-next-line PhanPossiblyUndeclaredVariable $res has at at least one item
-				$encValue = $dbr->addQuotes( $row->$field );
-				if ( $nextCond === '' ) {
-					$nextCond = "$field > $encValue";
-				} else {
-					$nextCond = "$field > $encValue OR ($field = $encValue AND ($nextCond))";
-				}
+				$conds[ $field ] = $row->$field;
 			}
-			$indexConds = [ $nextCond ];
+			$indexConds = [ $dbr->buildComparison( '>', $conds ) ];
 		}
 
 		$this->output( "Finished $table... $this->updated of $this->processed rows updated\n" );