BuildChunkChecksumSQL 构造分批计算CRC32聚合结果的SQL，或者分批计算每行CRC32值的SQL。 这里分批范围是 (rangeMin, rangeMax] ，第一批是 [rangeMin, rangeMax] 最终SQL类似：select /* dataChecksum */ COALESCE(LOWER(CONV(BIT_XOR(cast(crc32(CONCAT_WS('#',id, ftime, c1, c2)) as UNSIGNED)), 10, 16)), 0) as CRC32XOR OR COALESCE(LOWER(CONV(cast(crc32(CONCAT_WS('#',id, ftime, c1, c2)) as UNSIGNED), 10, 16)), 0) as CRC32 from test.t_time where (((col1 > ?) or ((col1 = ?) and (col2 > ?)) or (((col1 = ?) and (col2 = ?)) and (col3 > ?))) and ((col1 < ?) or ((col1 = ?) and (col2 < ?)) or (((col1 = ?) and (col2 = ?)) and (col3 < ?)) or ((col1 = ?) and (col2 = ?) and (col3 = ?)))).

BuildEqualsComparison 返回所有columns的条件表达式，譬如((col1 = ?) and (col2 = ?) and (col3 = ?)).

BuildEqualsPreparedComparison 构造columns的where条件等值表达式，譬如((col1 = ?) and (col2 = ?) and (col3 = ?)).

BuildRangeChecksumPreparedQuery 返回分批计算CRC32的checksum值的SQL，这里分批范围是 (rangeMin, rangeMax] ，第一批是 [rangeMin, rangeMax].

BuildRangeComparison 构造唯一键的分批范围查询where条件 返回结果类似"result = ((col1 > ?) or ((col1 = ?) and (col2 > ?)) or (((col1 = ?) and (col2 = ?)) and (col3 > ?)) or ((col1 = ?) and (col2 = ?) and (col3 = ?)))" 返回结果类似"explodedArgs = [v1, v1, v2, v1, v2, v3, v1, v2, v3]".

BuildRangePreparedComparison 返回唯一键的分批[上限/下限]范围查询where条件.

BuildSetPreparedClause 构造update语句的set子句，譬如 col1=?, col2=?.

BuildUniqueKeyMaxValuesPreparedQuery 构造查询唯一键最大值的SQL.

BuildUniqueKeyMinValuesPreparedQuery 构造查询唯一键最小值的SQL.

BuildUniqueKeyRangeEndPreparedQueryViaOffset 构造分批范围的分批下限值查询SQL 最终SQL类似：select /* gh-ost db.tab iteration:5 */ col1, col2, col3 from db.tab where ((col1 > ?) or ((col1 = ?) and (col2 > ?)) or (((col1 = ?) and (col2 = ?)) and (col3 > ?))) and ((col1 < ?) or ((col1 = ?) and (col2 < ?)) or (((col1 = ?) and (col2 = ?)) and (col3 < ?)) or ((col1 = ?) and (col2 = ?) and (col3 = ?))) order by col1 asc, col2 asc, col3 asc limit 1 offset {chunkSize -1}.

BuildUniqueKeyRangeEndPreparedQueryViaTemptable 构造分批范围的分批下限值查询SQL，与BuildUniqueKeyRangeEndPreparedQueryViaOffset稍有差异 最终SQL类似： select /* dataChecksum db.tab iteration:5 */ col1, col2, col3 from ( select col1, col2, col3 from db.tab where ((col1 > ?) or ((col1 = ?) and (col2 > ?)) or (((col1 = ?) and (col2 = ?)) and (col3 > ?))) and ((col1 < ?) or ((col1 = ?) and (col2 < ?)) or (((col1 = ?) and (col2 = ?)) and (col3 < ?)) or ((col1 = ?) and (col2 = ?) and (col3 = ?))) order by col1 asc, col2 asc, col3 asc limit {chunkSize} ) select_osc_chunk order by col1 desc, col2 desc, col3 desc limit 1.

BuildValueComparison 构造比较表达式，譬如 "(column = ?) 或者 (column > ?)".

EscapeName will escape a db/table/column/..

NewColumnList creates an object given ordered list of column names.

NewColumnValues 将abstractValues的值复制到ValuesPointers.

ParseColumnList parses a comma delimited list of column names.

ColumnList makes for a named list of columns.

UniqueKey is the combination of a key's name and columns.

ColumnsMap maps a column name onto its ordinal position.