Performance improvement for metadata queries that join against the COLUMNS metadata table.

h2/src/docsrc/html/changelog.html

@@ -21,6 +21,8 @@ Change Log
 
 <h2>Next Version (unreleased)</h2>
 <ul>
+<li>Performance improvement for metadata queries that join against the COLUMNS metadata table.
+</li>
 <li>An ArrayIndexOutOfBoundsException was thrown in some cases
     when opening an old version 1.3 database, or an 1.4 database with
     both "mv_store=false" and the system property "h2.storeLocalTime" set to false.

h2/src/main/org/h2/table/MetaTable.java

@@ -17,7 +17,6 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Locale;
-
 import org.h2.command.Command;
 import org.h2.constraint.Constraint;
 import org.h2.constraint.ConstraintCheck;
@@ -128,7 +127,7 @@ public class MetaTable extends Table {
         this.type = type;
         Column[] cols;
         String indexColumnName = null;
-        switch (type) {
+        switch(type) {
         case TABLES:
             setObjectName("TABLES");
             cols = createColumns(
@@ -815,7 +814,16 @@ public class MetaTable extends Table {
             break;
         }
         case INDEXES: {
-            for (Table table : getAllTables(session)) {
+            // reduce the number of tables to scan - makes some metadata queries
+            // 10x faster
+            final ArrayList<Table> tablesToList;
+            if (indexFrom != null && indexTo != null && indexFrom.equals(indexTo)) {
+                String tableName = identifier(indexFrom.getString());
+                tablesToList = getTablesByName(session, tableName);
+            } else {
+                tablesToList = getAllTables(session);
+            }
+            for (Table table : tablesToList) {
                 String tableName = identifier(table.getName());
                 if (!checkIndex(session, tableName, indexFrom, indexTo)) {
                     continue;
@@ -1854,7 +1862,7 @@ public class MetaTable extends Table {
     }
 
     private static int getRefAction(int action) {
-        switch (action) {
+        switch(action) {
         case ConstraintReferential.CASCADE:
             return DatabaseMetaData.importedKeyCascade;
         case ConstraintReferential.RESTRICT: