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refactor: 优化分页查询代码。
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Suomm
parent
6034a49116
commit
209ec6ab60
@ -20,7 +20,10 @@ import com.mybatisflex.core.field.FieldQueryBuilder;
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import com.mybatisflex.core.mybatis.MappedStatementTypes;
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import com.mybatisflex.core.paginate.Page;
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import com.mybatisflex.core.provider.EntitySqlProvider;
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import com.mybatisflex.core.query.*;
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import com.mybatisflex.core.query.CPI;
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import com.mybatisflex.core.query.QueryColumn;
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import com.mybatisflex.core.query.QueryCondition;
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import com.mybatisflex.core.query.QueryWrapper;
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import com.mybatisflex.core.table.TableInfo;
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import com.mybatisflex.core.table.TableInfoFactory;
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import com.mybatisflex.core.util.*;
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@ -667,47 +670,39 @@ public interface BaseMapper<T> {
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default <R> Page<R> paginateAs(Page<R> page, QueryWrapper queryWrapper, Class<R> asType, Consumer<FieldQueryBuilder<R>>... consumers) {
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List<QueryColumn> selectColumns = CPI.getSelectColumns(queryWrapper);
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List<QueryOrderBy> orderBys = CPI.getOrderBys(queryWrapper);
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List<Join> joins = CPI.getJoins(queryWrapper);
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try {
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// 只有 totalRow 小于 0 的时候才会去查询总量
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// 这样方便用户做总数缓存，而非每次都要去查询总量
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// 一般的分页场景中，只有第一页的时候有必要去查询总量，第二页以后是不需要的
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if (page.getTotalRow() < 0) {
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QueryWrapper countQueryWrapper = MapperUtil.optimizeCountQueryWrapper(queryWrapper);
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long count = selectCountByQuery(countQueryWrapper);
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page.setTotalRow(count);
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page.setTotalRow(selectCountByQuery(countQueryWrapper));
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}
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if (page.isEmpty()) {
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return page;
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}
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//重置 selectColumns
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CPI.setSelectColumns(queryWrapper, selectColumns);
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//重置 orderBys
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CPI.setOrderBys(queryWrapper, orderBys);
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//重置 join
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CPI.setJoins(queryWrapper, joins);
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int offset = page.getPageSize() * (page.getPageNumber() - 1);
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queryWrapper.limit(offset, page.getPageSize());
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List<R> records;
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if (asType != null) {
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List<R> records = selectListByQueryAs(queryWrapper, asType);
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MapperUtil.queryFields(this, records, consumers);
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page.setRecords(records);
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records = selectListByQueryAs(queryWrapper, asType);
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} else {
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List<R> records = (List<R>) selectListByQuery(queryWrapper);
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records = (List<R>) selectListByQuery(queryWrapper);
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}
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MapperUtil.queryFields(this, records, consumers);
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page.setRecords(records);
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}
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// 将之前设置的 limit 清除掉
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CPI.setLimitRows(queryWrapper, null);
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CPI.setLimitOffset(queryWrapper, null);
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return page;
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} finally {
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// 将之前设置的 limit 清除掉
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// 保险起见把重置代码放到 finally 代码块中
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CPI.setLimitRows(queryWrapper, null);
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CPI.setLimitOffset(queryWrapper, null);
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}
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}
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@ -19,7 +19,9 @@ import com.mybatisflex.core.FlexConsts;
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import com.mybatisflex.core.exception.FlexExceptions;
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import com.mybatisflex.core.paginate.Page;
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import com.mybatisflex.core.provider.RowSqlProvider;
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import com.mybatisflex.core.query.*;
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import com.mybatisflex.core.query.CPI;
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import com.mybatisflex.core.query.QueryColumn;
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import com.mybatisflex.core.query.QueryWrapper;
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import com.mybatisflex.core.util.CollectionUtil;
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import com.mybatisflex.core.util.MapperUtil;
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import com.mybatisflex.core.util.StringUtil;
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@ -431,47 +433,35 @@ public interface RowMapper {
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* @return
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*/
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default Page<Row> paginate(String schema, String tableName, Page<Row> page, QueryWrapper queryWrapper) {
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try {
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CPI.setFromIfNecessary(queryWrapper, schema, tableName);
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List<QueryColumn> selectColumns = CPI.getSelectColumns(queryWrapper);
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List<QueryOrderBy> orderBys = CPI.getOrderBys(queryWrapper);
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List<Join> joins = CPI.getJoins(queryWrapper);
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// 只有 totalRow 小于 0 的时候才会去查询总量
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// 这样方便用户做总数缓存，而非每次都要去查询总量
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// 一般的分页场景中，只有第一页的时候有必要去查询总量，第二页以后是不需要的
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if (page.getTotalRow() < 0) {
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QueryWrapper countQueryWrapper = MapperUtil.optimizeCountQueryWrapper(queryWrapper);
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long count = selectCountByQuery(schema, tableName, countQueryWrapper);
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page.setTotalRow(count);
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page.setTotalRow(selectCountByQuery(schema, tableName, countQueryWrapper));
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}
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if (page.isEmpty()) {
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return page;
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}
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//重置 selectColumns
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CPI.setSelectColumns(queryWrapper, selectColumns);
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//重置 orderBys
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CPI.setOrderBys(queryWrapper, orderBys);
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//重置 join
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CPI.setJoins(queryWrapper, joins);
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int offset = page.getPageSize() * (page.getPageNumber() - 1);
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queryWrapper.limit(offset, page.getPageSize());
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List<Row> records = selectListByQuery(schema, tableName, queryWrapper);
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page.setRecords(records);
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// 将之前设置的 limit 清除掉
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CPI.setLimitRows(queryWrapper, null);
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CPI.setLimitOffset(queryWrapper, null);
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page.setRecords(selectListByQuery(schema, tableName, queryWrapper));
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return page;
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} finally {
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// 将之前设置的 limit 清除掉
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// 保险起见把重置代码放到 finally 代码块中
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CPI.setLimitRows(queryWrapper, null);
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CPI.setLimitOffset(queryWrapper, null);
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}
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}
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}
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@ -42,7 +42,7 @@ public class MapperUtil {
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*
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* <p><pre>
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* {@code
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* SELECT COUNT(*) AS `total` FROM ( ...用户构建的 SQL 语句... );
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* SELECT COUNT(*) AS `total` FROM ( ...用户构建的 SQL 语句... ) AS `t`;
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* }
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* </pre>
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*
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@ -58,22 +58,25 @@ public class MapperUtil {
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* 优化 COUNT 查询语句。
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*/
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public static QueryWrapper optimizeCountQueryWrapper(QueryWrapper queryWrapper) {
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List<QueryColumn> selectColumns = CPI.getSelectColumns(queryWrapper);
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List<QueryColumn> groupByColumns = CPI.getGroupByColumns(queryWrapper);
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// 对克隆对象进行操作，不影响原来的 QueryWrapper 对象
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QueryWrapper clone = queryWrapper.clone();
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// 将最后面的 order by 移除掉
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CPI.setOrderBys(clone, null);
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// 获取查询列和分组列，用于判断是否进行优化
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List<QueryColumn> selectColumns = CPI.getSelectColumns(clone);
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List<QueryColumn> groupByColumns = CPI.getGroupByColumns(clone);
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// 如果有 distinct 语句或者 group by 语句则不优化
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// 这种一旦优化了就会造成 count 语句查询出来的值不对
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if (hasDistinct(selectColumns) || hasGroupBy(groupByColumns)) {
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return rawCountQueryWrapper(queryWrapper);
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return rawCountQueryWrapper(clone);
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}
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// 判断能不能清除 join 语句
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if (canClearJoins(queryWrapper)) {
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CPI.setJoins(queryWrapper, null);
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if (canClearJoins(clone)) {
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CPI.setJoins(clone, null);
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}
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// 最后将最后面的 order by 移除掉
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// 将 select 里面的列换成 COUNT(*) AS `total` 就好了
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CPI.setOrderBys(queryWrapper, null);
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CPI.setSelectColumns(queryWrapper, Collections.singletonList(count().as("total")));
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return queryWrapper;
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// 将 select 里面的列换成 COUNT(*) AS `total`
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CPI.setSelectColumns(clone, Collections.singletonList(count().as("total")));
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return clone;
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}
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private static boolean hasDistinct(List<QueryColumn> selectColumns) {
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