fix(sql): count groups for HEAD requests with @group - #884

背景

issue #624 反馈：[] 里带 @group 时，total 拿到的是组内数量而不是分组后的总条数。

复现请求（issue 里的原始 JSON）：

{
  "[]": {
    "VehicleList_count": {
      "vehicleid$": "鄂QD24S8_0%",
      "sumdate%": "2023-10-15,2023-10-17",
      "@group": "vehicleid,sumdate",
      "@column": "vehicleid;sumdate;max(cnt):maxcnt",
      "@order": "maxcnt-"
    },
    "page": 0,
    "count": 5
  },
  "total@": "/[]/total"
}

原因

gainColumnString 在 HEAD 请求下把 SELECT 换成 count(*)，但 gainConditionString 对 HEAD 仍然拼接 GROUP BY，于是生成：

SELECT count(*) AS `count` FROM `sys`.`Vehicle` GROUP BY `vid`,`sdate`

这条 SQL 返回的是每一组的行数（多行），不是分组后的组数，所以 total 语义错位。Oracle 分支（isOracle() || isDameng() || isKingBaseOracle()）早就用外层 count(*) 包了一层子查询，其它库没有对应处理。

修复

在 gainSelectSQL 里对齐 Oracle 的写法：@group 非空且是 HEAD 方法时，把原语句包成子查询再 count(*)：

if (StringUtil.isNotEmpty(getGroup(), true) && RequestMethod.isHeadMethod(getMethod(), true)) {
    String sql = "SELECT " + (getCache() == JSONMap.CACHE_RAM ? "SQL_NO_CACHE " : "")
            + column + " FROM " + gainConditionString(tablePath, this);
    return explain + "SELECT count(*)" + gainAs() + getQuote() + JSONResponse.KEY_COUNT + getQuote()
            + " FROM (" + sql + ")" + gainAs() + gainSQLAliasWithQuote();
}

MySQL / SQL Server 要求 FROM 子查询有别名，用已有的 gainSQLAliasWithQuote() 补上，各库引号风格自动适配。

修复后：

-- MySQL
SELECT count(*) AS `count` FROM (SELECT count(*) AS `count` FROM `sys`.`Vehicle` GROUP BY `vid`,`sdate`) AS `Vehicle`
-- PostgreSQL
SELECT count(*) AS "count" FROM (SELECT count(*) AS "count" FROM "sys"."Vehicle" GROUP BY "vid","sdate") AS "Vehicle"

测试

新增 AbstractSQLConfigGroupCountTest，覆盖：

• MySQL / PostgreSQL / SQL Server / DB2 分组 HEAD 都断言外层 count(*) + 子查询结构，且外层不再出现 GROUP BY
• 没有 @group 时保持原来的单层 count(*)，不包子查询
• GET + @group 保持原样，不被改成 count(*)

双通道验证

修复前（git checkout 还原 AbstractSQLConfig.java）：

[ERROR] AbstractSQLConfigGroupCountTest.countsGroupsInsteadOfRowsInEachGroupForMySQL:87
    HEAD with @group on MYSQL: SELECT count(*) AS `count` FROM `sys`.`Vehicle` GROUP BY `vid`,`sdate`
[ERROR] Tests run: 6, Failures: 4, Errors: 0, Skipped: 0

修复后：

[INFO] Tests run: 6, Failures: 0, Errors: 0, Skipped: 0 -- in apijson.orm.AbstractSQLConfigGroupCountTest
[INFO] Tests run: 44, Failures: 0, Errors: 0, Skipped: 0
[INFO] BUILD SUCCESS

全量 mvn test 44 个用例全绿（原有 38 + 新增 6），无回归。

fix #624