87 lines
2.7 KiB
Go
87 lines
2.7 KiB
Go
// Copyright 2020 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package executor
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import (
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"github.com/cznic/mathutil"
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"github.com/pingcap/tidb/sessionctx"
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"github.com/pingcap/tidb/util/chunk"
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"github.com/pingcap/tidb/util/kvcache"
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"github.com/pingcap/tidb/util/memory"
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"github.com/pingcap/tidb/util/stringutil"
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)
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// applyCache is used in the apply executor. When we get the same value of the outer row.
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// We fetch the inner rows in the cache not to fetch them in the inner executor.
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type applyCache struct {
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cache *kvcache.SimpleLRUCache
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memCapacity int64
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memTracker *memory.Tracker // track memory usage.
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}
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type applyCacheKey []byte
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func (key applyCacheKey) Hash() []byte {
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return key
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}
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func applyCacheKVMem(key applyCacheKey, value *chunk.List) int64 {
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return int64(len(key)) + value.GetMemTracker().BytesConsumed()
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}
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func newApplyCache(ctx sessionctx.Context) (*applyCache, error) {
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// since applyCache controls the memory usage by itself, set the capacity of
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// the underlying LRUCache to max to close its memory control
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cache := kvcache.NewSimpleLRUCache(mathutil.MaxUint, 0.1, 0)
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c := applyCache{
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cache: cache,
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memCapacity: ctx.GetSessionVars().NestedLoopJoinCacheCapacity,
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memTracker: memory.NewTracker(stringutil.StringerStr("applyCache"), -1),
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}
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return &c, nil
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}
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// Get gets a cache item according to cache key.
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func (c *applyCache) Get(key applyCacheKey) (*chunk.List, error) {
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value, hit := c.cache.Get(&key)
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if !hit {
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return nil, nil
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}
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typedValue := value.(*chunk.List)
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return typedValue, nil
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}
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// Set inserts an item to the cache.
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func (c *applyCache) Set(key applyCacheKey, value *chunk.List) (bool, error) {
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mem := applyCacheKVMem(key, value)
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if mem > c.memCapacity { // ignore this kv pair if its size is too large
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return false, nil
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}
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for mem+c.memTracker.BytesConsumed() > c.memCapacity {
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evictedKey, evictedValue, evicted := c.cache.RemoveOldest()
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if !evicted {
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return false, nil
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}
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c.memTracker.Consume(-applyCacheKVMem(evictedKey.(applyCacheKey), evictedValue.(*chunk.List)))
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}
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c.memTracker.Consume(mem)
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c.cache.Put(key, value)
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return true, nil
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}
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// GetMemTracker returns the memory tracker of this apply cache.
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func (c *applyCache) GetMemTracker() *memory.Tracker {
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return c.memTracker
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}
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