4. 单查询不能有效利用多核
• 对某些查询,可以并行处理
• 例如:SELECT count(*) FROM table WHERE
col1 BETWEEN a AND b;
• 我们完全可以把[a,b]区间分成小区间并发:
• SELECT count(*) FROM table WHERE col1
BETWEEN a AND x1;
• SELECT count(*) FROM table WHERE col1
BETWEEN x1 AND x2;
• …
• SELECT count(*) FROM table WHERE col1
BETWEEN xn AND b;