AliSQL: [Feature] Issue#15 DDL FAST FAIL

Summary:

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The feature provides a way to set lock wait timeout for ddl statements.

Usage:

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alter table t [wait [n]|no_wait] add f int,

drop table [wait [n]|no_wait], etc.

no_wait: the query not wait for locks, return immediately, and print

"ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction;"

wait [n]: n is the wait time in second, after wait n seconds for locks,

return and print errors;