Add info about slow query tables #262
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crazycs520
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Dec 12, 2024
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| The protobuf messages are defined in [`diagnosticspb.proto`](https://github.com/pingcap/kvproto/blob/master/proto/diagnosticspb.proto) in the `pingcap/kvproto` repo. Key messages are `SearchLogRequest` and `SearchLogResponse`. | ||
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| This table uses the [`clusterLogRetriever`](https://github.com/pingcap/tidb/blob/1521bf723dd023da655add0f883acaab5ee69683/pkg/executor/memtable_reader.go#L361) with the [`ClusterLogTableExtractor`](https://github.com/pingcap/tidb/blob/1521bf723dd023da655add0f883acaab5ee69683/pkg/planner/core/memtable_predicate_extractor.go#L756). |
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These descriptions are not quite right, CLUSTER_SLOW_QUERY is actually implemented through the coprocessor grpc interface, which is the same as a normal cop request, except that it sends the cop request to the TiDB node, which allows for the reuse of query conditions push down and column prune, to reduces transfer unnecessary data.
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What is changed:
This adds information on the workings of the
SLOW_QUERYandCLUSTER_SLOW_QUERYtables.