sqlserver2005的分頁優化

這篇文章主要介紹“sqlserver2005的分頁優化”，在日常操作中，相信很多人在sqlserver2005的分頁優化問題上存在疑惑，小編查閱了各式資料，整理出簡單好用的操作方法，希望對大家解答”sqlserver2005的分頁優化”的疑惑有所幫助！接下來，請跟著小編一起來學習吧！

一、hibernate分頁 hibernate對MsSql的偽分頁
分頁是web項目中比不可少的一個功能，數據量大的時候不能全部展示必然要用到分頁技術。相信大家對hibernate中的分頁都不陌生：
Java代碼 
public Query setMaxResults(int maxResults);  
public Query setFirstResult(int firstResult); 
Java代碼 
public Query setMaxResults(int maxResults); 
public Query setFirstResult(int firstResult); 

只要調用了這兩個方法并設置好參數，hibernate自動分頁完全屏蔽了底層分頁技術，這也是眾多開發者喜歡hibernate的原因之一。
項目開發中遇到一個奇怪的問題。數據庫采用的是Sql Server 2005，也設置了上面兩個參數，可是每次發送到數據庫端的SQL語句都是select top ....語句。即便是查詢第10w條，也只有一個select top 語句，不免引起對hibernate實現sql server分頁的懷疑。hibernate針對不同數據庫實現的分頁方法封裝在對應數據庫的方言里，通過getLimitString方法轉化成對應數據庫的分頁算法。
以常見的Mysql數據庫的方言MySQLDialect為例：
Java代碼 
public String getLimitString(String sql, boolean hasOffset) {  
        return new StringBuffer( sql.length() + 20 )  
                .append( sql )  
                .append( hasOffset ? " limit ?, ?" : " limit ?" )  
                .toString();  
    } 
Java代碼 
public String getLimitString(String sql, boolean hasOffset) { 
        return new StringBuffer( sql.length() + 20 ) 
                .append( sql ) 
                .append( hasOffset ? " limit ?, ?" : " limit ?" ) 
                .toString(); 
    } 

采用了大家熟悉的的limit進行分頁。
數據庫的方言Oracle9iDialect：
Java代碼 
StringBuffer pagingSelect = new StringBuffer( sql.length()+100 );  
        if (hasOffset) {  
            pagingSelect.append("select * from ( select row_.*, rownum rownum_ from ( ");  
        }  
        else {  
            pagingSelect.append("select * from ( ");  
        }  
        pagingSelect.append(sql);  
        if (hasOffset) {  
            pagingSelect.append(" ) row_ where rownum <= ?) where rownum_ > ?");  
        }  
        else {  
            pagingSelect.append(" ) where rownum <= ?");  
        } 
Java代碼 
StringBuffer pagingSelect = new StringBuffer( sql.length()+100 ); 
        if (hasOffset) { 
            pagingSelect.append("select * from ( select row_.*, rownum rownum_ from ( "); 
        } 
        else { 
            pagingSelect.append("select * from ( "); 
        } 
        pagingSelect.append(sql); 
        if (hasOffset) { 
            pagingSelect.append(" ) row_ where rownum <= ?) where rownum_ > ?"); 
        } 
        else { 
            pagingSelect.append(" ) where rownum <= ?"); 
        } 

利用Oracle的rownum 結合三層嵌套查詢完成分頁。這個三層是Oracle最經典高效的分頁算法。
可是針對Sql Server的方言SQLServerDialect：
Java代碼 
public String getLimitString(String querySelect, int offset, int limit) {  
        if ( offset > 0 ) {  
            throw new UnsupportedOperationException( "query result offset is not supported" );  
        }  
        return new StringBuffer( querySelect.length() + 8 )  
                .append( querySelect )  
                .insert( getAfterSelectInsertPoint( querySelect ), " top " + limit )  
                .toString();  
    } 
Java代碼 
public String getLimitString(String querySelect, int offset, int limit) { 
        if ( offset > 0 ) { 
            throw new UnsupportedOperationException( "query result offset is not supported" ); 
        } 
        return new StringBuffer( querySelect.length() + 8 ) 
                .append( querySelect ) 
                .insert( getAfterSelectInsertPoint( querySelect ), " top " + limit ) 
                .toString(); 
    } 

揉揉眼睛、再揉揉，沒錯，只出現了一個top語句。這就意味著如果查詢第10w頁的數據，需要把前10w頁數據全部提取出來。hibernate針對sql server的分頁是偽分頁，所以隨著數據量日益增加用戶抱怨系統速度慢，程序員抱怨hibernate性能低，dba抱怨開發人員sql功底太淺。
不知道hibernate開發組，出于什么目前或情況沒有真正提供sql server的分頁技術，那我們自己來實現。
方言類：
Java代碼 
public class SQLServer2005Dialect extends SQLServerDialect {  
 
    /** 
     *  
     * 是否需要綁定limit參數? 
     *  
     * 在SQL Server中使用top時不能使用參數表示top條數,而使用ROW_NUMBER()則需要提供limit參數 
     */ 
 
    private ThreadLocal<Boolean> supportsVariableLimit = new ThreadLocal<Boolean>();  
    public SQLServer2005Dialect() {  
        registerFunction("bitand", new BitAndFunction());  
        registerFunction("bitxor", new BitXorFunction());  
        registerFunction("bitor", new BitOrFunction());  
        setSupportsVariableLimit(false);  
    }  
 
    /** 
     *  
     * <p> 
     * 設置是否先綁定limit參數。 
     * </p> 
     *  
     * @param first 
     */ 
 
    private void setSupportsVariableLimit(boolean first) {  
        this.supportsVariableLimit.set(Boolean.valueOf(first));  
    }  
 
    /** 
     *  
     * <p> 
     * 獲取sql中select子句位置。 
     * </p> 
     *  
     * @param sql 
     *  
     * @return int 
     */ 
    protected static int getSqlAfterSelectInsertPoint(String sql) {  
        int selectIndex = sql.toLowerCase().indexOf("select");  
 
        int selectDistinctIndex = sql.toLowerCase().indexOf("select distinct");  
 
        return selectIndex + ((selectDistinctIndex == selectIndex) ? 15 : 6);  
    }  
 
    public boolean supportsLimitOffset() {  
        return true;  
    }  
 
    /* 
     * Hibernate在獲得Limit String(已添加了limit子句)后，如果此方法返回true， 
     *  
     * 則會添加額外的參數值(ROW_NUMBER()范圍)(策略可能是這樣：有offset設置兩個參數值，沒有設置一個參數值) 
     */ 
    public boolean supportsVariableLimit() {  
        return ((Boolean) this.supportsVariableLimit.get()).booleanValue();  
    }  
 
    public boolean useMaxForLimit() {  
        return true;  
    }  
    /** 
     * 首頁top，以后用ROW_NUMBER 
     */ 
    public String getLimitString(String query, int offset, int limit) {  
        setSupportsVariableLimit(offset > 0);  
 
        if (offset == 0) {  
            return new StringBuffer(query.length() + 8).append(query).insert(  
                    getSqlAfterSelectInsertPoint(query), " top " + limit)  
                    .toString();  
        }  
 
        return getLimitString(query, offset > 0);  
    }  
      
    public String getLimitString(String sql, boolean hasOffset) {  
        int orderByIndex = sql.toLowerCase().lastIndexOf("order by");  
 
        if (orderByIndex <= 0) {  
            throw new UnsupportedOperationException(  
                    "must specify 'order by' statement to support limit operation with offset in sql server 2005");  
        }  
 
        String sqlOrderBy = sql.substring(orderByIndex + 8);  
 
        String sqlRemoveOrderBy = sql.substring(0, orderByIndex);  
 
        int insertPoint = getSqlAfterSelectInsertPoint(sql);  
        return new StringBuffer(sql.length() + 100)  
                .append("with tempPagination as(")  
                .append(sqlRemoveOrderBy)  
                .insert(  
                        insertPoint + 23,  
                        " ROW_NUMBER() OVER(ORDER BY " + sqlOrderBy  
                                + ") as RowNumber,")  
                .append(  
                        ") select * from tempPagination where RowNumber>?  and RowNumber<=?")  
                .toString();  
    }  
} 
Java代碼 
public class SQLServer2005Dialect extends SQLServerDialect { 
 
    /**
     * 
     * 是否需要綁定limit參數?
     * 
     * 在SQL Server中使用top時不能使用參數表示top條數,而使用ROW_NUMBER()則需要提供limit參數
     */ 
 
    private ThreadLocal<Boolean> supportsVariableLimit = new ThreadLocal<Boolean>(); 
    public SQLServer2005Dialect() { 
        registerFunction("bitand", new BitAndFunction()); 
        registerFunction("bitxor", new BitXorFunction()); 
        registerFunction("bitor", new BitOrFunction()); 
        setSupportsVariableLimit(false); 
    } 
 
    /**
     * 
     * <p>
     * 設置是否先綁定limit參數。
     * </p>
     * 
     * @param first
     */ 
 
    private void setSupportsVariableLimit(boolean first) { 
        this.supportsVariableLimit.set(Boolean.valueOf(first)); 
    } 
 
    /**
     * 
     * <p>
     * 獲取sql中select子句位置。
     * </p>
     * 
     * @param sql
     * 
     * @return int
     */ 
    protected static int getSqlAfterSelectInsertPoint(String sql) { 
        int selectIndex = sql.toLowerCase().indexOf("select"); 
 
        int selectDistinctIndex = sql.toLowerCase().indexOf("select distinct"); 
 
        return selectIndex + ((selectDistinctIndex == selectIndex) ? 15 : 6); 
    } 
 
    public boolean supportsLimitOffset() { 
        return true; 
    } 
 
    /*
     * Hibernate在獲得Limit String(已添加了limit子句)后，如果此方法返回true，
     * 
     * 則會添加額外的參數值(ROW_NUMBER()范圍)(策略可能是這樣：有offset設置兩個參數值，沒有設置一個參數值)
     */ 
    public boolean supportsVariableLimit() { 
        return ((Boolean) this.supportsVariableLimit.get()).booleanValue(); 
    } 
 
    public boolean useMaxForLimit() { 
        return true; 
    } 
    /**
     * 首頁top，以后用ROW_NUMBER
     */ 
    public String getLimitString(String query, int offset, int limit) { 
        setSupportsVariableLimit(offset > 0); 
 
        if (offset == 0) { 
            return new StringBuffer(query.length() + 8).append(query).insert( 
                    getSqlAfterSelectInsertPoint(query), " top " + limit) 
                    .toString(); 
        } 
 
        return getLimitString(query, offset > 0); 
    } 
     
    public String getLimitString(String sql, boolean hasOffset) { 
        int orderByIndex = sql.toLowerCase().lastIndexOf("order by"); 
 
        if (orderByIndex <= 0) { 
            throw new UnsupportedOperationException( 
                    "must specify 'order by' statement to support limit operation with offset in sql server 2005"); 
        } 
 
        String sqlOrderBy = sql.substring(orderByIndex + 8); 
 
        String sqlRemoveOrderBy = sql.substring(0, orderByIndex); 
 
        int insertPoint = getSqlAfterSelectInsertPoint(sql); 
        return new StringBuffer(sql.length() + 100) 
                .append("with tempPagination as(") 
                .append(sqlRemoveOrderBy) 
                .insert( 
                        insertPoint + 23, 
                        " ROW_NUMBER() OVER(ORDER BY " + sqlOrderBy 
                                + ") as RowNumber,") 
                .append( 
                        ") select * from tempPagination where RowNumber>?  and RowNumber<=?") 
                .toString(); 
    } 
} 

函數：
Java代碼 
public class BitAndFunction implements SQLFunction {  
    public Type getReturnType(Type type, Mapping mapping) {  
        return Hibernate.INTEGER;  
    }  
 
    public boolean hasArguments() {  
        return true;  
    }  
 
    public boolean hasParenthesesIfNoArguments() {  
        return true;  
    }  
 
    public String render(List args, SessionFactoryImplementor factory)  
            throws QueryException {  
        if (args.size() != 2) {  
            throw new IllegalArgumentException(  
                    "BitAndFunction requires 2 arguments!");  
        }  
        return args.get(0).toString() + " & " + args.get(1).toString();  
    }  
} 
Java代碼 
public class BitAndFunction implements SQLFunction { 
    public Type getReturnType(Type type, Mapping mapping) { 
        return Hibernate.INTEGER; 
    } 
 
    public boolean hasArguments() { 
        return true; 
    } 
 
    public boolean hasParenthesesIfNoArguments() { 
        return true; 
    } 
 
    public String render(List args, SessionFactoryImplementor factory) 
            throws QueryException { 
        if (args.size() != 2) { 
            throw new IllegalArgumentException( 
                    "BitAndFunction requires 2 arguments!"); 
        } 
        return args.get(0).toString() + " & " + args.get(1).toString(); 
    } 
} 
 
Java代碼 
public class BitOrFunction implements SQLFunction {  
    public Type getReturnType(Type type, Mapping mapping) {  
        return Hibernate.INTEGER;  
    }  
    public boolean hasArguments() {  
        return true;  
    }  
    public boolean hasParenthesesIfNoArguments() {  
        return true;  
    }  
    public String render(List args, SessionFactoryImplementor factory)  
            throws QueryException {  
        if (args.size() != 2) {  
            throw new IllegalArgumentException(  
                    "BitOrFunction requires 2 arguments!");  
        }  
        return args.get(0).toString() + " | " + args.get(1).toString();  
    }  
} 
Java代碼 
public class BitOrFunction implements SQLFunction { 
    public Type getReturnType(Type type, Mapping mapping) { 
        return Hibernate.INTEGER; 
    } 
    public boolean hasArguments() { 
        return true; 
    } 
    public boolean hasParenthesesIfNoArguments() { 
        return true; 
    } 
    public String render(List args, SessionFactoryImplementor factory) 
            throws QueryException { 
        if (args.size() != 2) { 
            throw new IllegalArgumentException( 
                    "BitOrFunction requires 2 arguments!"); 
        } 
        return args.get(0).toString() + " | " + args.get(1).toString(); 
    } 
} 
 
Java代碼 
public Type getReturnType(Type type, Mapping mapping) {  
        return Hibernate.INTEGER;  
    }  
    public boolean hasArguments() {  
        return true;  
    }  
    public boolean hasParenthesesIfNoArguments() {  
        return true;  
    }  
    public String render(List args, SessionFactoryImplementor factory)  
            throws QueryException {  
        if (args.size() != 2) {  
            throw new IllegalArgumentException(  
                    "BitXorFunction requires 2 arguments!");  
        }  
        return args.get(0).toString() + " ^ " + args.get(1).toString();  
    } 

到此，關于“sqlserver2005的分頁優化”的學習就結束了，希望能夠解決大家的疑惑。理論與實踐的搭配能更好的幫助大家學習，快去試試吧！若想繼續學習更多相關知識，請繼續關注億速云網站，小編會繼續努力為大家帶來更多實用的文章！