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

3 files changed, 15 insertions, 36 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" );
diff --git a/maintenance/namespaceDupes.php b/maintenance/namespaceDupes.php
index 3e1ff809b9b5..e44275aa6c15 100644
--- a/maintenance/namespaceDupes.php
+++ b/maintenance/namespaceDupes.php
@@ -488,14 +488,13 @@ class NamespaceDupes extends Maintenance {
 				$this->resolvableLinks -= $dbw->affectedRows();
 			}
 
-			// @phan-suppress-next-line PhanPossiblyUndeclaredVariable rows contains at least one item
-			$encLastTitle = $dbw->addQuotes( $row->$titleField );
-			// @phan-suppress-next-line PhanPossiblyUndeclaredVariable rows contains at least one item
-			$encLastFrom = $dbw->addQuotes( $row->$fromField );
-
 			$batchConds = [
-				"$titleField > $encLastTitle " .
-				"OR ($titleField = $encLastTitle AND $fromField > $encLastFrom)"
+				$dbw->buildComparison( '>', [
+					// @phan-suppress-next-line PhanPossiblyUndeclaredVariable rows contains at least one item
+					$titleField => $dbw->addQuotes( $row->$titleField ),
+					// @phan-suppress-next-line PhanPossiblyUndeclaredVariable rows contains at least one item
+					$fromField => $dbw->addQuotes( $row->$fromField ),
+				] )
 			];
 
 			$lbFactory->waitForReplication();
diff --git a/maintenance/updateCollation.php b/maintenance/updateCollation.php
index 6230ef09d140..3f6bb19096ec 100644
--- a/maintenance/updateCollation.php
+++ b/maintenance/updateCollation.php
@@ -271,31 +271,19 @@ TEXT
 		} else {
 			$fields = [ 'cl_collation', 'cl_to', 'cl_type', 'cl_from' ];
 		}
-		$first = true;
-		$cond = false;
-		$prefix = false;
+		$conds = [];
 		foreach ( $fields as $field ) {
 			if ( $dbw->getType() === 'mysql' && $field === 'cl_type' ) {
 				// Range conditions with enums are weird in mysql
 				// This must be a numeric literal, or it won't work.
-				$encValue = intval( $row->cl_type_numeric );
+				$value = intval( $row->cl_type_numeric );
 			} else {
-				$encValue = $dbw->addQuotes( $row->$field );
-			}
-			$inequality = "$field > $encValue";
-			$equality = "$field = $encValue";
-			if ( $first ) {
-				$cond = $inequality;
-				$prefix = $equality;
-				$first = false;
-			} else {
-				// @phan-suppress-next-line PhanTypeSuspiciousStringExpression False positive
-				$cond .= " OR ($prefix AND $inequality)";
-				$prefix .= " AND $equality";
+				$value = $row->$field;
 			}
+			$conds[ $field ] = $value;
 		}
 
-		return $cond;
+		return $dbw->buildComparison( '>', $conds );
 	}
 
 	/**