static __always_inline__u32 parse_postgres_server_resp(char *buf, int buf_size) { // Return immeadiately if buffer is empty if (buf_size < 1) { return 0; } // Read the first byte from the buffer // This should be the identifier of the PostgresQL message ch...
intparse_client_postgres_data(char*buf,int buf_size,__u8*request_type){// Return immeadiately if buffer is emptyif(buf_size<1){return0;}// Read the first byte from the buffer// This should be the identifier of the PostgresQL messagechar identifier;if(bpf_probe_read(&identifier,sizeof(...
int parse_client_postgres_data(char *buf, int buf_size, __u8 *request_type) { // Return immeadiately if buffer is empty if (buf_size< 1) { return 0; } // Read the first byte from the buffer // This should be theidentifierof the PostgresQL message char identifier; if (bpf_probe...
如果要修改buffer table slot内的内容, 需要加bufmappinglock exclusive lock, 注意这个是锁整个buffer table, 为了提高吞吐, PG 把buffer table分成了几个partition, 修改一个buffer table slot时, 锁这个slot对应的partition(也就是说, 同一个partition内的slot只能串行修改, 但是也大幅度减少了修改buffer table 的...
Buffer ID 描述符的几种状态 Empty: When the corresponding buffer pool slot does not store a page (i.e. refcount and usage_count are 0), the state of this descriptor is empty. Pinned: When the corresponding buffer pool slot stores a page and any PostgreSQL processes are accessing the page...
TupleTableSlot也可以是空的,不持有任何有效数据。这种状态只在刚创建的还没有赋上元组描述符的slot上有效。在这种状态,tts_isempty必须为true,tts_shouldFree为false,tts_tuple为NULL,tts_buffer为InvalidBuffer,并且tts_nvalid为零。 TupleTableSlot只简单引用元组描述符,而不复制。ExecSetSlotDescriptor()的调用者负...
缓冲区表层是存放buffer_tags和buffer_ids关系的哈希表,buffer_ids表示存储的数据页的元数据buffer描述符的序号,而buffer_tags是关系表数据页的标识符(The buffer table is a hash table that stores the relations between the buffer_tags of stored pages and the buffer_ids of the descriptors that hold the ...
* ourselves, and the output buffer is empty, it's time to exit * streaming. */if(streamingDoneReceiving&&streamingDoneSending&&!pq_is_send_pending())break; 重点: pq_is_send_pending表示libpq是不是正在发送(判断发出缓冲区是不是有数据) ...
本地缓冲区管理器(local buffer manager)为temporary表(无需WAL-logged或checkpointed)进行快速缓冲区管理,API定义在src/backend/storage/buffer/localbuf.c中。 获取LocalBuffer 初始化 首先解释temp_buffers GUC参数,其用于设置session使用的temporary buffers的最大数量,对应的变量为num_temp_buffers。InitLocalBuffers函...
若没找到有用的边界keys，则需要调用_bt_endpoint从第一页开始，否则调用_bt_search从BTree的root节点_bt_getroot开始扫描，直至找到符合扫描键和快照的第一个叶子节点，之后调用二分查找_bt_binsrch找到符合扫描键的页内item偏移，最后将找到的页面载入到buffer中并返回tuple。_bt_next函数会从当前页中尝试获取下...