MONDRIAN: Reinstate support for "ORDER BY ... NULLS LAST" per MONDRIA…

…N-618. This implementation is more conservative; it assumes that a database does not support the syntax unless JdbcDialectImpl.supportsOrderByNullsLast() is overridden. [git-p4: depot-paths = "//open/mondrian-release/3.1/": change = 13068]
pentaho · Sep 29, 2009 · 1b5fb05 · 1b5fb05
1 parent 385ce83
commit 1b5fb05
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Showing 4 changed files with 73 additions and 18 deletions.
diff --git a/src/main/mondrian/spi/impl/FirebirdDialect.java b/src/main/mondrian/spi/impl/FirebirdDialect.java
@@ -37,6 +37,10 @@ public FirebirdDialect(Connection connection) throws SQLException {
     public boolean allowsAs() {
         return false;
     }
+
+    public boolean supportsOrderByNullsLast() {
+        return true;
+    }
 }
 
 // End FirebirdDialect.java
diff --git a/src/main/mondrian/spi/impl/JdbcDialectImpl.java b/src/main/mondrian/spi/impl/JdbcDialectImpl.java
@@ -9,7 +9,6 @@
 package mondrian.spi.impl;
 
 import mondrian.olap.Util;
-import mondrian.olap.MondrianDef;
 import mondrian.spi.*;
 
 import java.util.*;
@@ -704,13 +703,55 @@ public String generateOrderItem(
         boolean nullable,
         boolean ascending)
     {
-        if (ascending) {
-            return expr + " ASC";
+        if (nullable) {
+            NullCollation collateLast = getNullCollation();
+            switch (collateLast) {
+            case NEGINF:
+                // For DESC, NULLs already appear last.
+                // For ASC, we need to reverse the order.
+                // Use the SQL standard syntax 'ORDER BY x ASC NULLS LAST'.
+                if (ascending) {
+                    return expr + " ASC"
+                       + (supportsOrderByNullsLast() ? " NULLS LAST" : "");
+                } else {
+                    return expr + " DESC";
+                }
+            case POSINF:
+                if (ascending) {
+                    return expr + " ASC";
+                } else {
+                    return expr + " DESC"
+                       + (supportsOrderByNullsLast() ? " NULLS LAST" : "");
+                }
+            default:
+                throw Util.unexpected(collateLast);
+            }
         } else {
-            return expr + " DESC";
+            if (ascending) {
+                return expr + " ASC";
+            } else {
+                return expr + " DESC";
+            }
         }
     }
 
+    /**
+     * Returns whether this dialect supports "ASC NULLS LAST" and "DESC NULLS
+     * LAST" applied to an item in the ORDER BY clause.
+     *
+     * <p>This feature is in standard SQL but is not supported by many
+     * databases, therefore the default implementation returns {@code false}.
+     *
+     * <p>This method is only called from
+     * {@link #generateOrderItem(String, boolean, boolean)}. Some dialects
+     * override that method and therefore never call this method.
+     *
+     * @return Whether this dialect supports "ORDER BY ... NULLS LAST".
+     */
+    public boolean supportsOrderByNullsLast() {
+        return false;
+    }
+
     public boolean supportsGroupByExpressions() {
         return true;
     }
@@ -779,11 +820,12 @@ public static DatabaseProduct getProduct(
         String productName,
         String productVersion)
     {
+        final String upperProductName = productName.toUpperCase();
         if (productName.equals("ACCESS")) {
             return DatabaseProduct.ACCESS;
-        } else if (productName.trim().toUpperCase().equals("APACHE DERBY")) {
+        } else if (upperProductName.trim().equals("APACHE DERBY")) {
             return DatabaseProduct.DERBY;
-        } else if (productName.trim().toUpperCase().equals("DBMS:CLOUDSCAPE")) {
+        } else if (upperProductName.trim().equals("DBMS:CLOUDSCAPE")) {
             return DatabaseProduct.DERBY;
         } else if (productName.startsWith("DB2")) {
             if (productName.startsWith("DB2 UDB for AS/400")) {
@@ -808,37 +850,37 @@ public static DatabaseProduct getProduct(
                 // DB2 on NT returns "DB2/NT"
                 return DatabaseProduct.DB2;
             }
-        } else if (productName.toUpperCase().indexOf("FIREBIRD") >= 0) {
+        } else if (upperProductName.indexOf("FIREBIRD") >= 0) {
             return DatabaseProduct.FIREBIRD;
         } else if (productName.startsWith("Informix")) {
             return DatabaseProduct.INFORMIX;
-        } else if (productName.toUpperCase().equals("INGRES")) {
+        } else if (upperProductName.equals("INGRES")) {
             return DatabaseProduct.INGRES;
         } else if (productName.equals("Interbase")) {
             return DatabaseProduct.INTERBASE;
-        } else if (productName.toUpperCase().equals("LUCIDDB")) {
+        } else if (upperProductName.equals("LUCIDDB")) {
             return DatabaseProduct.LUCIDDB;
-        } else if (productName.toUpperCase().indexOf("SQL SERVER") >= 0) {
+        } else if (upperProductName.indexOf("SQL SERVER") >= 0) {
             return DatabaseProduct.MSSQL;
         } else if (productName.equals("Oracle")) {
             return DatabaseProduct.ORACLE;
-        } else if (productName.toUpperCase().indexOf("POSTGRE") >= 0) {
+        } else if (upperProductName.indexOf("POSTGRE") >= 0) {
             return DatabaseProduct.POSTGRESQL;
-        } else if (productName.toUpperCase().indexOf("NETEZZA") >= 0) {
+        } else if (upperProductName.indexOf("NETEZZA") >= 0) {
             return DatabaseProduct.NETEZZA;
-        } else if (productName.toUpperCase().equals("MYSQL (INFOBRIGHT)")) {
+        } else if (upperProductName.equals("MYSQL (INFOBRIGHT)")) {
             return DatabaseProduct.INFOBRIGHT;
-        } else if (productName.toUpperCase().equals("MYSQL")) {
+        } else if (upperProductName.equals("MYSQL")) {
             return DatabaseProduct.MYSQL;
         } else if (productName.startsWith("HP Neoview")) {
             return DatabaseProduct.NEOVIEW;
-        } else if (productName.toUpperCase().indexOf("SYBASE") >= 0) {
+        } else if (upperProductName.indexOf("SYBASE") >= 0) {
             return DatabaseProduct.SYBASE;
-        } else if (productName.toUpperCase().indexOf("TERADATA") >= 0) {
+        } else if (upperProductName.indexOf("TERADATA") >= 0) {
             return DatabaseProduct.TERADATA;
-        } else if (productName.toUpperCase().indexOf("HSQL") >= 0) {
+        } else if (upperProductName.indexOf("HSQL") >= 0) {
             return DatabaseProduct.HSQLDB;
-        } else if (productName.toUpperCase().indexOf("VERTICA") >= 0) {
+        } else if (upperProductName.indexOf("VERTICA") >= 0) {
             return DatabaseProduct.VERTICA;
         } else {
             return DatabaseProduct.UNKNOWN;

diff --git a/src/main/mondrian/spi/impl/OracleDialect.java b/src/main/mondrian/spi/impl/OracleDialect.java
@@ -52,6 +52,10 @@ public String generateInline(
     public boolean supportsGroupingSets() {
         return true;
     }
+
+    public boolean supportsOrderByNullsLast() {
+        return true;
+    }
 }
 
 // End OracleDialect.java
diff --git a/src/main/mondrian/spi/impl/PostgreSqlDialect.java b/src/main/mondrian/spi/impl/PostgreSqlDialect.java
@@ -37,6 +37,11 @@ public PostgreSqlDialect(Connection connection) throws SQLException {
     public boolean requiresAliasForFromQuery() {
         return true;
     }
+
+    public boolean supportsOrderByNullsLast() {
+        // Support for "ORDER BY ... NULLS LAST" was introduced in Postgres 8.3.
+        return productVersion.compareTo("8.3") >= 0;
+    }
 }
 
 // End PostgreSqlDialect.java