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53 lines
1.3 KiB
Text
53 lines
1.3 KiB
Text
create or replace table t1 (col1 char(10) character set ucs2, filler char(100), key(col1)) ;
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insert into t1 values ('a', 'a');
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insert into t1 values ('a', 'a');
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set optimizer_trace=1;
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explain format=json select * from t1 force index(col1) where col1 >='a';
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EXPLAIN
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{
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"query_block": {
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"select_id": 1,
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"nested_loop": [
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{
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"table": {
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"table_name": "t1",
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"access_type": "range",
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"possible_keys": ["col1"],
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"key": "col1",
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"key_length": "21",
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"used_key_parts": ["col1"],
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"rows": 2,
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"filtered": 100,
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"index_condition": "t1.col1 >= 'a'"
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}
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}
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]
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}
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}
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select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
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JS
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[
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{
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"range_scan_alternatives":
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[
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{
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"index": "col1",
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"ranges":
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["(a) <= (col1)"],
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"rowid_ordered": false,
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"using_mrr": false,
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"index_only": false,
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"rows": 2,
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"cost": 2.547733708,
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"chosen": true
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}
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],
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"analyzing_roworder_intersect":
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{
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"cause": "too few roworder scans"
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},
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"analyzing_index_merge_union":
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[]
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}
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]
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drop table t1;
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