limit number of rows different per table

Author: guyplusplus

README.md

@@ -12,6 +12,8 @@ The tool compares md5 of the row, simply speaking `select concat(pk1, pk2) PK, m
 
 The tool being optimized for tables very similar in content, it retrieves 1 row alternatively from master then slave table. As data is sorted by PK, it keeps a sorted list of differences (pk and md5 value) in memory. As soon as there is a match, any value lower than the match pair is immediately reported and removed from memory. Memory footprint shall then remain small.
 
+In the case the tool finds more than N rows (N=100 by default) different, the tool proceeds to analyze the next table.
+
 ## Build and Test
 
 Build only requires Maven and Java 7.

src/main/java/com/geckotechnology/mySqlDataCompare/MySQLTableDataComparer.java

@@ -10,6 +10,8 @@
 
 public class MySQLTableDataComparer {
 
+	private static final int MAX_DIFFERENCES_PER_TABLE = 100;
+	
 	private ArrayList<SchemaDifference> dataDifferences = new ArrayList<SchemaDifference>();
 	private MySQLSchemaRetriever masterSchemaReader;
 	private MySQLSchemaRetriever slaveSchemaReader;
@@ -41,6 +43,7 @@ public void compareTable(Table table) throws Exception {
 		ArrayList<OneRow> unmatchedSlaveRows = new ArrayList<OneRow>();
 		boolean hasMasterResultSetNext = true;
 		boolean hasSlaveResultSetNext = true;
+		int dataDifferencesSizeAtStart = dataDifferences.size();
 
 		while(hasMasterResultSetNext && hasSlaveResultSetNext) {
 			//Get 1 row from master DB
@@ -57,6 +60,27 @@ public void compareTable(Table table) throws Exception {
 			}
 			else
 				hasSlaveResultSetNext = false;
+			//check now there are not too many differences
+			if((dataDifferences.size() - dataDifferencesSizeAtStart) > MAX_DIFFERENCES_PER_TABLE) {
+				dataDifferences.add(new SchemaDifference(Criticality.ERROR,
+						table.getTableName(),
+						DifferenceType.DATA_TOO_MANY_DIFFERENCES,
+						"max rows:" + MAX_DIFFERENCES_PER_TABLE
+						));			
+				break;
+			}
+			if(unmatchedMasterRows.size() > MAX_DIFFERENCES_PER_TABLE ||
+					unmatchedSlaveRows.size() > MAX_DIFFERENCES_PER_TABLE) {
+				dataDifferences.add(new SchemaDifference(Criticality.ERROR,
+						table.getTableName(),
+						DifferenceType.DATA_TOO_MANY_UNMATCHED_ROWS,
+						"max rows:" + MAX_DIFFERENCES_PER_TABLE
+						));
+				//clearing the rows as it is not sure they are unmatched
+				unmatchedMasterRows.clear();
+				unmatchedSlaveRows.clear();
+				break;
+			}
 		}
 
 		//rows not found in slave table

src/main/java/com/geckotechnology/mySqlDataCompare/SchemaDifference.java

@@ -21,7 +21,9 @@ enum DifferenceType {
 		COLUMN_DIFFERENT_PRIMARY_KEY,
 		DATA_ROW_DIFFERENT_MD5,
 		DATA_ROW_MISSING_IN_SLAVE_TABLE,
-		DATA_ROW_EXCESS_IN_SLAVE_TABLE
+		DATA_ROW_EXCESS_IN_SLAVE_TABLE,
+		DATA_TOO_MANY_UNMATCHED_ROWS,
+		DATA_TOO_MANY_DIFFERENCES		
 	}
 
 	private Criticality criticality;