使用步骤:
SHOW VARIABLES LIKE "optimizer_trace";
# SET OPTIMIZER_TRACE="enabled=on",END_MARKERS_IN_JSON=on;
SET OPTIMIZER_TRACE="enabled=on";
SET optimizer_trace_offset=-30, optimizer_trace_limit=30;
select * from ai_chat.wechat_users order by openid limit 100;
SELECT * FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE;
SET optimizer_trace="enabled=off";












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