本节继续介绍排序的实现,上一节介绍了tuplesort_begin_heap/tuplesort_puttupleslot,本节介绍的函数是tuplesort_performsort. ### 一、数据结构 **TupleTableSlot** 执行器在"tuple table"中存储元组,这个表是各自独立的TupleTableSlots链表. ``` /*---------- * The executor stores tuples in a "tuple table" which is a List of * independent TupleTableSlots. There are several cases we need to handle: * 1. physical tuple in a disk buffer page * 2. physical tuple constructed in palloc'ed memory * 3. "minimal" physical tuple constructed in palloc'ed memory * 4. "virtual" tuple consisting of Datum/isnull arrays * 执行器在"tuple table"中存储元组,这个表是各自独立的TupleTableSlots链表. * 有以下情况需要处理: * 1. 磁盘缓存页中的物理元组 * 2. 在已分配内存中构造的物理元组 * 3. 在已分配内存中构造的"minimal"物理元组 * 4. 含有Datum/isnull数组的"virtual"虚拟元组 * * The first two cases are similar in that they both deal with "materialized" * tuples, but resource management is different. For a tuple in a disk page * we need to hold a pin on the buffer until the TupleTableSlot's reference * to the tuple is dropped; while for a palloc'd tuple we usually want the * tuple pfree'd when the TupleTableSlot's reference is dropped. * 最上面2种情况跟"物化"元组的处理方式类似,但资源管理是不同的. * 对于在磁盘页中的元组,需要pin在缓存中直至TupleTableSlot依赖的元组被清除, * 而对于通过palloc分配的元组在TupleTableSlot依赖被清除后通常希望使用pfree释放 * * A "minimal" tuple is handled similarly to a palloc'd regular tuple. * At present, minimal tuples never are stored in buffers, so there is no * parallel to case 1. Note that a minimal tuple has no "system columns". * (Actually, it could have an OID, but we have no need to access the OID.) * "minimal"元组与通常的palloc分配的元组处理类似. * 截止目前为止,"minimal"元组不会存储在缓存中,因此对于第一种情况不会存在并行的问题. * 注意"minimal"没有"system columns"系统列 * (实际上,可以有OID,但不需要访问OID列) * * A "virtual" tuple is an optimization used to minimize physical data * copying in a nest of plan nodes. Any pass-by-reference Datums in the * tuple point to storage that is not directly associated with the * TupleTableSlot; generally they will point to part of a tuple stored in * a lower plan node's output TupleTableSlot, or to a function result * constructed in a plan node's per-tuple econtext. It is the responsibility * of the generating plan node to be sure these resources are not released * for as long as the virtual tuple needs to be valid. We only use virtual * tuples in the result slots of plan nodes --- tuples to be copied anywhere * else need to be "materialized" into physical tuples. Note also that a * virtual tuple does not have any "system columns". * "virtual"元组是用于在嵌套计划节点中拷贝时最小化物理数据的优化. * 所有通过引用传递指向与TupleTableSlot非直接相关的存储的元组的Datums使用, * 通常它们会指向存储在低层节点输出的TupleTableSlot中的元组的一部分, * 或者指向在计划节点的per-tuple内存上下文econtext中构造的函数结果. * 产生计划节点的时候有责任确保这些资源未被释放,确保virtual元组是有效的. * 我们使用计划节点中的结果slots中的虚拟元组 --- 元组会拷贝到其他地方需要"物化"到物理元组中. * 注意virtual元组不需要有"system columns" * * It is also possible for a TupleTableSlot to hold both physical and minimal * copies of a tuple. This is done when the slot is requested to provide * the format other than the one it currently holds. (Originally we attempted * to handle such requests by replacing one format with the other, but that * had the fatal defect of invalidating any pass-by-reference Datums pointing * into the existing slot contents.) Both copies must contain identical data * payloads when this is the case. * TupleTableSlot包含物理和minimal元组拷贝是可能的. * 在slot需要提供格式化而不是当前持有的格式时会出现这种情况. * (原始的情况是我们准备通过另外一种格式进行替换来处理这种请求,但在校验引用传递Datums时会出现致命错误) * 同时在这种情况下,拷贝必须含有唯一的数据payloads. * * The Datum/isnull arrays of a TupleTableSlot serve double duty. When the * slot contains a virtual tuple, they are the authoritative data. When the * slot contains a physical tuple, the arrays contain data extracted from * the tuple. (In this state, any pass-by-reference Datums point into * the physical tuple.) The extracted information is built "lazily", * ie, only as needed. This serves to avoid repeated extraction of data * from the physical tuple. * TupleTableSlot中的Datum/isnull数组有双重职责. * 在slot包含虚拟元组时,它们是authoritative(权威)数据. * 在slot包含物理元组时,时包含从元组中提取的数据的数组. * (在这种情况下,所有通过引用传递的Datums指向物理元组) * 提取的信息通过'lazily'在需要的时候才构建. * 这样可以避免从物理元组的重复数据提取. * * A TupleTableSlot can also be "empty", holding no valid data. This is * the only valid state for a freshly-created slot that has not yet had a * tuple descriptor assigned to it. In this state, tts_isempty must be * true, tts_shouldFree false, tts_tuple NULL, tts_buffer InvalidBuffer, * and tts_nvalid zero. * TupleTableSlot可能为"empty",没有有效数据. * 对于新鲜创建仍未分配描述的的slot来说这是唯一有效的状态. * 在这种状态下,tts_isempty必须为T,tts_shouldFree为F, tts_tuple为NULL, * tts_buffer为InvalidBuffer,tts_nvalid为0. * * The tupleDescriptor is simply referenced, not copied, by the TupleTableSlot * code. The caller of ExecSetSlotDescriptor() is responsible for providing * a descriptor that will live as long as the slot does. (Typically, both * slots and descriptors are in per-query memory and are freed by memory * context deallocation at query end; so it's not worth providing any extra * mechanism to do more. However, the slot will increment the tupdesc * reference count if a reference-counted tupdesc is supplied.) * tupleDescriptor只是简单的引用并没有通过TupleTableSlot中的代码进行拷贝. * ExecSetSlotDescriptor()的调用者有责任提供与slot生命周期一样的描述符. * (典型的,不管是slots还是描述符会在per-query内存中, * 并且会在查询结束时通过内存上下文的析构器释放,因此不需要提供额外的机制来处理. * 但是,如果使用了引用计数型tupdesc,slot会增加tupdesc引用计数) * * When tts_shouldFree is true, the physical tuple is "owned" by the slot * and should be freed when the slot's reference to the tuple is dropped. * 在tts_shouldFree为T的情况下,物理元组由slot持有,并且在slot引用元组被清除时释放内存. * * If tts_buffer is not InvalidBuffer, then the slot is holding a pin * on the indicated buffer page; drop the pin when we release the * slot's reference to that buffer. (tts_shouldFree should always be * false in such a case, since presumably tts_tuple is pointing at the * buffer page.) * 如tts_buffer不是InvalidBuffer,那么slot持有缓存页中的pin,在释放引用该buffer的slot时会清除该pin. * (tts_shouldFree通常来说应为F,因为tts_tuple会指向缓存页) * * tts_nvalid indicates the number of valid columns in the tts_values/isnull * arrays. When the slot is holding a "virtual" tuple this must be equal * to the descriptor's natts. When the slot is holding a physical tuple * this is equal to the number of columns we have extracted (we always * extract columns from left to right, so there are no holes). * tts_nvalid指示了tts_values/isnull数组中的有效列数. * 如果slot含有虚拟元组,该字段必须跟描述符的natts一样. * 在slot含有物理元组时,该字段等于我们提取的列数. * (我们通常从左到右提取列,因此不会有空洞存在) * * tts_values/tts_isnull are allocated when a descriptor is assigned to the * slot; they are of length equal to the descriptor's natts. * 在描述符分配给slot时tts_values/tts_isnull会被分配内存,长度与描述符natts长度一样. * * tts_mintuple must always be NULL if the slot does not hold a "minimal" * tuple. When it does, tts_mintuple points to the actual MinimalTupleData * object (the thing to be pfree'd if tts_shouldFreeMin is true). If the slot * has only a minimal and not also a regular physical tuple, then tts_tuple * points at tts_minhdr and the fields of that struct are set correctly * for access to the minimal tuple; in particular, tts_minhdr.t_data points * MINIMAL_TUPLE_OFFSET bytes before tts_mintuple. This allows column * extraction to treat the case identically to regular physical tuples. * 如果slot没有包含minimal元组,tts_mintuple通常必须为NULL. * 如含有,则tts_mintuple执行实际的MinimalTupleData对象(如tts_shouldFreeMin为T,则需要通过pfree释放内存). * 如果slot只有一个minimal而没有通常的物理元组,那么tts_tuple指向tts_minhdr, * 结构体的其他字段会被正确的设置为用于访问minimal元组. * 特别的, tts_minhdr.t_data指向tts_mintuple前的MINIMAL_TUPLE_OFFSET字节. * 这可以让列提取可以独立处理通常的物理元组. * * tts_slow/tts_off are saved state for slot_deform_tuple, and should not * be touched by any other code. * tts_slow/tts_off用于存储slot_deform_tuple状态,不应通过其他代码修改. *---------- */ typedef struct TupleTableSlot { NodeTag type;//Node标记 //如slot为空,则为T bool tts_isempty; /* true = slot is empty */ //是否需要pfree tts_tuple? bool tts_shouldFree; /* should pfree tts_tuple? */ //是否需要pfree tts_mintuple? bool tts_shouldFreeMin; /* should pfree tts_mintuple? */ #define FIELDNO_TUPLETABLESLOT_SLOW 4 //为slot_deform_tuple存储状态? bool tts_slow; /* saved state for slot_deform_tuple */ #define FIELDNO_TUPLETABLESLOT_TUPLE 5 //物理元组,如为虚拟元组则为NULL HeapTuple tts_tuple; /* physical tuple, or NULL if virtual */ #define FIELDNO_TUPLETABLESLOT_TUPLEDESCRIPTOR 6 //slot中的元组描述符 TupleDesc tts_tupleDescriptor; /* slot's tuple descriptor */ //slot所在的上下文 MemoryContext tts_mcxt; /* slot itself is in this context */ //元组缓存,如无则为InvalidBuffer Buffer tts_buffer; /* tuple's buffer, or InvalidBuffer */ #define FIELDNO_TUPLETABLESLOT_NVALID 9 //tts_values中的有效值 int tts_nvalid; /* # of valid values in tts_values */ #define FIELDNO_TUPLETABLESLOT_VALUES 10 //当前每个属性的值 Datum *tts_values; /* current per-attribute values */ #define FIELDNO_TUPLETABLESLOT_ISNULL 11 //isnull数组 bool *tts_isnull; /* current per-attribute isnull flags */ //minimal元组,如无则为NULL MinimalTuple tts_mintuple; /* minimal tuple, or NULL if none */ //在minimal情况下的工作空间 HeapTupleData tts_minhdr; /* workspace for minimal-tuple-only case */ #define FIELDNO_TUPLETABLESLOT_OFF 14 //slot_deform_tuple的存储状态 uint32 tts_off; /* saved state for slot_deform_tuple */ //不能被变更的描述符(固定描述符) bool tts_fixedTupleDescriptor; /* descriptor can't be changed */ } TupleTableSlot; /* base tuple table slot type */ typedef struct TupleTableSlot { NodeTag type;//Node标记 #define FIELDNO_TUPLETABLESLOT_FLAGS 1 uint16 tts_flags; /* 布尔状态;Boolean states */ #define FIELDNO_TUPLETABLESLOT_NVALID 2 AttrNumber tts_nvalid; /* 在tts_values中有多少有效的values;# of valid values in tts_values */ const TupleTableSlotOps *const tts_ops; /* slot的实际实现;implementation of slot */ #define FIELDNO_TUPLETABLESLOT_TUPLEDESCRIPTOR 4 TupleDesc tts_tupleDescriptor; /* slot的元组描述符;slot's tuple descriptor */ #define FIELDNO_TUPLETABLESLOT_VALUES 5 Datum *tts_values; /* 当前属性值;current per-attribute values */ #define FIELDNO_TUPLETABLESLOT_ISNULL 6 bool *tts_isnull; /* 当前属性isnull标记;current per-attribute isnull flags */ MemoryContext tts_mcxt; /*内存上下文; slot itself is in this context */ } TupleTableSlot; /* routines for a TupleTableSlot implementation */ //TupleTableSlot的"小程序" struct TupleTableSlotOps { /* Minimum size of the slot */ //slot的最小化大小 size_t base_slot_size; /* Initialization. */ //初始化方法 void (*init)(TupleTableSlot *slot); /* Destruction. */ //析构方法 void (*release)(TupleTableSlot *slot); /* * Clear the contents of the slot. Only the contents are expected to be * cleared and not the tuple descriptor. Typically an implementation of * this callback should free the memory allocated for the tuple contained * in the slot. * 清除slot中的内容。 * 只希望清除内容，而不希望清除元组描述符。 * 通常，这个回调的实现应该释放为slot中包含的元组分配的内存。 */ void (*clear)(TupleTableSlot *slot); /* * Fill up first natts entries of tts_values and tts_isnull arrays with * values from the tuple contained in the slot. The function may be called * with natts more than the number of attributes available in the tuple, * in which case it should set tts_nvalid to the number of returned * columns. * 用slot中包含的元组的值填充tts_values和tts_isnull数组的第一个natts条目。 * 在调用该函数时，natts可能多于元组中可用属性的数量，在这种情况下， * 应该将tts_nvalid设置为返回列的数量。 */ void (*getsomeattrs)(TupleTableSlot *slot, int natts); /* * Returns value of the given system attribute as a datum and sets isnull * to false, if it's not NULL. Throws an error if the slot type does not * support system attributes. * 将给定系统属性的值作为基准返回，如果不为NULL， * 则将isnull设置为false。如果slot类型不支持系统属性，则引发错误。 */ Datum (*getsysattr)(TupleTableSlot *slot, int attnum, bool *isnull); /* * Make the contents of the slot solely depend on the slot, and not on * underlying resources (like another memory context, buffers, etc). * 使slot的内容完全依赖于slot，而不是底层资源(如另一个内存上下文、缓冲区等)。 */ void (*materialize)(TupleTableSlot *slot); /* * Copy the contents of the source slot into the destination slot's own * context. Invoked using callback of the destination slot. * 将源slot的内容复制到目标slot自己的上下文中。 * 使用目标slot的回调函数调用。 */ void (*copyslot) (TupleTableSlot *dstslot, TupleTableSlot *srcslot); /* * Return a heap tuple "owned" by the slot. It is slot's responsibility to * free the memory consumed by the heap tuple. If the slot can not "own" a * heap tuple, it should not implement this callback and should set it as * NULL. * 返回slot“拥有”的堆元组。 * slot负责释放堆元组分配的内存。 * 如果slot不能“拥有”堆元组，它不应该实现这个回调函数，应该将它设置为NULL。 */ HeapTuple (*get_heap_tuple)(TupleTableSlot *slot); /* * Return a minimal tuple "owned" by the slot. It is slot's responsibility * to free the memory consumed by the minimal tuple. If the slot can not * "own" a minimal tuple, it should not implement this callback and should * set it as NULL. * 返回slot“拥有”的最小元组。 * slot负责释放最小元组分配的内存。 * 如果slot不能“拥有”最小元组，它不应该实现这个回调函数，应该将它设置为NULL。 */ MinimalTuple (*get_minimal_tuple)(TupleTableSlot *slot); /* * Return a copy of heap tuple representing the contents of the slot. The * copy needs to be palloc'd in the current memory context. The slot * itself is expected to remain unaffected. It is *not* expected to have * meaningful "system columns" in the copy. The copy is not be "owned" by * the slot i.e. the caller has to take responsibilty to free memory * consumed by the slot. * 返回表示slot内容的堆元组副本。 * 需要在当前内存上下文中对副本进行内存分配palloc。 * 预计slot本身不会受到影响。 * 它不希望在副本中有有意义的“系统列”。副本不是slot“拥有”的，即调用方必须负责释放slot消耗的内存。 */ HeapTuple (*copy_heap_tuple)(TupleTableSlot *slot); /* * Return a copy of minimal tuple representing the contents of the slot. The * copy needs to be palloc'd in the current memory context. The slot * itself is expected to remain unaffected. It is *not* expected to have * meaningful "system columns" in the copy. The copy is not be "owned" by * the slot i.e. the caller has to take responsibilty to free memory * consumed by the slot. * 返回表示slot内容的最小元组的副本。 * 需要在当前内存上下文中对副本进行palloc。 * 预计slot本身不会受到影响。 * 它不希望在副本中有有意义的“系统列”。副本不是slot“拥有”的，即调用方必须负责释放slot消耗的内存。 */ MinimalTuple (*copy_minimal_tuple)(TupleTableSlot *slot); }; typedef struct tupleDesc { int natts; /* tuple中的属性数量;number of attributes in the tuple */ Oid tdtypeid; /* tuple类型的组合类型ID;composite type ID for tuple type */ int32 tdtypmod; /* tuple类型的typmode;typmod for tuple type */ int tdrefcount; /* 依赖计数,如为-1,则没有依赖;reference count, or -1 if not counting */ TupleConstr *constr; /* 约束,如无则为NULL;constraints, or NULL if none */ /* attrs[N] is the description of Attribute Number N+1 */ //attrs[N]是第N+1个属性的描述符 FormData_pg_attribute attrs[FLEXIBLE_ARRAY_MEMBER]; } *TupleDesc; ``` **SortState** 排序运行期状态信息 ``` /* ---------------- * SortState information * 排序运行期状态信息 * ---------------- */ typedef struct SortState { //基类 ScanState ss; /* its first field is NodeTag */ //是否需要随机访问排序输出? bool randomAccess; /* need random access to sort output? */ //结果集是否存在边界? bool bounded; /* is the result set bounded? */ //如存在边界,需要多少个元组? int64 bound; /* if bounded, how many tuples are needed */ //是否已完成排序? bool sort_Done; /* sort completed yet? */ //是否使用有界值? bool bounded_Done; /* value of bounded we did the sort with */ //使用的有界值? int64 bound_Done; /* value of bound we did the sort with */ //tuplesort.c的私有状态 void *tuplesortstate; /* private state of tuplesort.c */ //是否worker? bool am_worker; /* are we a worker? */ //每个worker对应一个条目 SharedSortInfo *shared_info; /* one entry per worker */ } SortState; /* ---------------- * Shared memory container for per-worker sort information * per-worker排序信息的共享内存容器 * ---------------- */ typedef struct SharedSortInfo { //worker个数? int num_workers; //排序机制 TuplesortInstrumentation sinstrument[FLEXIBLE_ARRAY_MEMBER]; } SharedSortInfo; ``` **TuplesortInstrumentation** 报告排序统计的数据结构. ``` /* * Data structures for reporting sort statistics. Note that * TuplesortInstrumentation can't contain any pointers because we * sometimes put it in shared memory. * 报告排序统计的数据结构. * 注意TuplesortInstrumentation不能包含指针因为有时候会把该结构体放在共享内存中. */ typedef enum { SORT_TYPE_STILL_IN_PROGRESS = 0,//仍然在排序中 SORT_TYPE_TOP_N_HEAPSORT,//TOP N 堆排序 SORT_TYPE_QUICKSORT,//快速排序 SORT_TYPE_EXTERNAL_SORT,//外部排序 SORT_TYPE_EXTERNAL_MERGE//外部排序后的合并 } TuplesortMethod;//排序方法 typedef enum { SORT_SPACE_TYPE_DISK,//需要用上磁盘 SORT_SPACE_TYPE_MEMORY//使用内存 } TuplesortSpaceType; typedef struct TuplesortInstrumentation { //使用的排序算法 TuplesortMethod sortMethod; /* sort algorithm used */ //排序使用空间类型 TuplesortSpaceType spaceType; /* type of space spaceUsed represents */ //空间消耗(以K为单位) long spaceUsed; /* space consumption, in kB */ } TuplesortInstrumentation; ``` ### 二、源码解读 tuplesort_performsort是排序的实现. ``` /* * All tuples have been provided; finish the sort. * 已存在元组,执行排序! */ void tuplesort_performsort(Tuplesortstate *state) { MemoryContext oldcontext = MemoryContextSwitchTo(state->sortcontext); #ifdef TRACE_SORT if (trace_sort) elog(LOG, "performsort of worker %d starting: %s", state->worker, pg_rusage_show(&state->ru_start)); #endif //根据状态执行不同的逻辑 switch (state->status) { case TSS_INITIAL: /* * We were able to accumulate all the tuples within the allowed * amount of memory, or leader to take over worker tapes * 可以在允许的内存大小中积累所有的元组,或者让协调者接管工作tapes. */ if (SERIAL(state)) { /* Just qsort 'em and we're done */ //快速排序 tuplesort_sort_memtuples(state); state->status = TSS_SORTEDINMEM; } else if (WORKER(state)) { /* * Parallel workers must still dump out tuples to tape. No * merge is required to produce single output run, though. * 并行worker必须dump元组到磁盘上. * 但是,生成单个输出运行不需要合并. */ inittapes(state, false); dumptuples(state, true); worker_nomergeruns(state); state->status = TSS_SORTEDONTAPE; } else { /* * Leader will take over worker tapes and merge worker runs. * Note that mergeruns sets the correct state->status. * 并行协调器会接管工作进程的数据并合并工作线程运行. * 注意mergeruns会设置正确的状态:state->status */ leader_takeover_tapes(state); mergeruns(state); } state->current = 0; state->eof_reached = false; state->markpos_block = 0L; state->markpos_offset = 0; state->markpos_eof = false; break; case TSS_BOUNDED://堆排序 /* * We were able to accumulate all the tuples required for output * in memory, using a heap to eliminate excess tuples. Now we * have to transform the heap to a properly-sorted array. * 使用堆来消除多余的元组,在内存可以积累所有的元组用于输出. * 现在我们必须转换堆为已排序的数组. */ sort_bounded_heap(state); state->current = 0; state->eof_reached = false; state->markpos_offset = 0; state->markpos_eof = false; state->status = TSS_SORTEDINMEM; break; case TSS_BUILDRUNS: /* * Finish tape-based sort. First, flush all tuples remaining in * memory out to tape; then merge until we have a single remaining * run (or, if !randomAccess and !WORKER(), one run per tape). * Note that mergeruns sets the correct state->status. * 完成tape-based排序. * 首先刷新所有在内存的元组到tape(持久化存储)上,然后合并直至只留下一个在运行. * (否则,如果!randomAccess 且 !WORKER(),一个tape运行一次) */ //全部刷到磁盘上 dumptuples(state, true); //合并执行 mergeruns(state); state->eof_reached = false; state->markpos_block = 0L; state->markpos_offset = 0; state->markpos_eof = false; break; default: elog(ERROR, "invalid tuplesort state"); break; } #ifdef TRACE_SORT if (trace_sort) { if (state->status == TSS_FINALMERGE) elog(LOG, "performsort of worker %d done (except %d-way final merge): %s", state->worker, state->activeTapes, pg_rusage_show(&state->ru_start)); else elog(LOG, "performsort of worker %d done: %s", state->worker, pg_rusage_show(&state->ru_start)); } #endif MemoryContextSwitchTo(oldcontext); } ``` ### 三、跟踪分析 测试脚本 ``` select * from t_sort order by c1,c2; ``` 跟踪分析 ``` (gdb) b tuplesort_begin_heap Breakpoint 1 at 0xa6ffa1: file tuplesort.c, line 812. (gdb) b tuplesort_puttupleslot Breakpoint 2 at 0xa7119d: file tuplesort.c, line 1436. (gdb) b tuplesort_performsort Breakpoint 3 at 0xa71f45: file tuplesort.c, line 1792. (gdb) c Continuing. Breakpoint 1, tuplesort_begin_heap (tupDesc=0x208fa40, nkeys=2, attNums=0x2081858, sortOperators=0x2081878, sortCollations=0x2081898, nullsFirstFlags=0x20818b8, workMem=4096, coordinate=0x0, randomAccess=false) at tuplesort.c:812 812 Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate, (gdb) ``` **tuplesort_begin_heap** 输入参数 ``` (gdb) p *tupDesc $1 = {natts = 7, tdtypeid = 2249, tdtypmod = -1, tdhasoid = false, tdrefcount = -1, constr = 0x0, attrs = 0x208fa60} (gdb) p *tupDesc->attrs $2 = {attrelid = 0, attname = {data = '\000' <repeats 63 times>}, atttypid = 1043, attstattarget = -1, attlen = -1, attnum = 1, attndims = 0, attcacheoff = -1, atttypmod = 24, attbyval = false, attstorage = 120 'x', attalign = 105 'i', attnotnull = false, atthasdef = false, atthasmissing = false, attidentity = 0 '\000', attisdropped = false, attislocal = true, attinhcount = 0, attcollation = 100} (gdb) p *attNums $3 = 2 (gdb) p *sortOperators $4 = 97 (gdb) p *sortCollations $5 = 0 (gdb) p nullsFirstFlags $6 = (_Bool *) 0x20818b8 (gdb) p *nullsFirstFlags $7 = false (gdb) ``` 获取排序状态,status = TSS_INITIAL ``` (gdb) p *state $8 = {status = TSS_INITIAL, nKeys = 0, randomAccess = false, bounded = false, boundUsed = false, bound = 0, tuples = true, availMem = 4169704, allowedMem = 4194304, maxTapes = 0, tapeRange = 0, sortcontext = 0x2093290, tuplecontext = 0x20992c0, tapeset = 0x0, comparetup = 0x0, copytup = 0x0, writetup = 0x0, readtup = 0x0, memtuples = 0x209b310, memtupcount = 0, memtupsize = 1024, growmemtuples = true, slabAllocatorUsed = false, slabMemoryBegin = 0x0, slabMemoryEnd = 0x0, slabFreeHead = 0x0, read_buffer_size = 0, lastReturnedTuple = 0x0, currentRun = 0, mergeactive = 0x0, Level = 0, destTape = 0, tp_fib = 0x0, tp_runs = 0x0, tp_dummy = 0x0, tp_tapenum = 0x0, activeTapes = 0, result_tape = -1, current = 0, eof_reached = false, markpos_block = 0, markpos_offset = 0, markpos_eof = false, worker = -1, shared = 0x0, nParticipants = -1, tupDesc = 0x0, sortKeys = 0x0, onlyKey = 0x0, abbrevNext = 0, indexInfo = 0x0, estate = 0x0, heapRel = 0x0, indexRel = 0x0, enforceUnique = false, high_mask = 0, low_mask = 0, max_buckets = 0, datumType = 0, datumTypeLen = 0, ru_start = {tv = {tv_sec = 0, tv_usec = 0}, ru = {ru_utime = {tv_sec = 0, tv_usec = 0}, ru_stime = { tv_sec = 0, tv_usec = 0}, {ru_maxrss = 0, __ru_maxrss_word = 0}, {ru_ixrss = 0, __ru_ixrss_word = 0}, { ru_idrss = 0, __ru_idrss_word = 0}, {ru_isrss = 0, __ru_isrss_word = 0}, {ru_minflt = 0, __ru_minflt_word = 0}, { ru_majflt = 0, __ru_majflt_word = 0}, {ru_nswap = 0, __ru_nswap_word = 0}, {ru_inblock = 0, __ru_inblock_word = 0}, {ru_oublock = 0, __ru_oublock_word = 0}, {ru_msgsnd = 0, __ru_msgsnd_word = 0}, {ru_msgrcv = 0, __ru_msgrcv_word = 0}, {ru_nsignals = 0, __ru_nsignals_word = 0}, {ru_nvcsw = 0, __ru_nvcsw_word = 0}, { ru_nivcsw = 0, __ru_nivcsw_word = 0}}}} ``` 设置运行状态 ``` (gdb) n 819 AssertArg(nkeys > 0); (gdb) 822 if (trace_sort) (gdb) 828 state->nKeys = nkeys; (gdb) 830 TRACE_POSTGRESQL_SORT_START(HEAP_SORT, (gdb) 837 state->comparetup = comparetup_heap; (gdb) 838 state->copytup = copytup_heap; (gdb) 839 state->writetup = writetup_heap; (gdb) 840 state->readtup = readtup_heap; (gdb) 842 state->tupDesc = tupDesc; /* assume we need not copy tupDesc */ (gdb) 843 state->abbrevNext = 10; (gdb) 846 state->sortKeys = (SortSupport) palloc0(nkeys * sizeof(SortSupportData)); (gdb) 848 for (i = 0; i < nkeys; i++) (gdb) p *state $9 = {status = TSS_INITIAL, nKeys = 2, randomAccess = false, bounded = false, boundUsed = false, bound = 0, tuples = true, availMem = 4169704, allowedMem = 4194304, maxTapes = 0, tapeRange = 0, sortcontext = 0x2093290, tuplecontext = 0x20992c0, tapeset = 0x0, comparetup = 0xa7525b <comparetup_heap>, copytup = 0xa76247 <copytup_heap>, writetup = 0xa76de1 <writetup_heap>, readtup = 0xa76ec6 <readtup_heap>, memtuples = 0x209b310, memtupcount = 0, memtupsize = 1024, growmemtuples = true, slabAllocatorUsed = false, slabMemoryBegin = 0x0, slabMemoryEnd = 0x0, slabFreeHead = 0x0, read_buffer_size = 0, lastReturnedTuple = 0x0, currentRun = 0, mergeactive = 0x0, Level = 0, destTape = 0, tp_fib = 0x0, tp_runs = 0x0, tp_dummy = 0x0, tp_tapenum = 0x0, activeTapes = 0, result_tape = -1, current = 0, eof_reached = false, markpos_block = 0, markpos_offset = 0, markpos_eof = false, worker = -1, shared = 0x0, nParticipants = -1, tupDesc = 0x208fa40, sortKeys = 0x20937c0, onlyKey = 0x0, abbrevNext = 10, indexInfo = 0x0, estate = 0x0, heapRel = 0x0, indexRel = 0x0, enforceUnique = false, high_mask = 0, low_mask = 0, max_buckets = 0, datumType = 0, datumTypeLen = 0, ru_start = {tv = {tv_sec = 0, tv_usec = 0}, ru = {ru_utime = {tv_sec = 0, tv_usec = 0}, ru_stime = {tv_sec = 0, tv_usec = 0}, {ru_maxrss = 0, __ru_maxrss_word = 0}, {ru_ixrss = 0, __ru_ixrss_word = 0}, { ru_idrss = 0, __ru_idrss_word = 0}, {ru_isrss = 0, __ru_isrss_word = 0}, {ru_minflt = 0, __ru_minflt_word = 0}, { ru_majflt = 0, __ru_majflt_word = 0}, {ru_nswap = 0, __ru_nswap_word = 0}, {ru_inblock = 0, __ru_inblock_word = 0}, {ru_oublock = 0, __ru_oublock_word = 0}, {ru_msgsnd = 0, __ru_msgsnd_word = 0}, {ru_msgrcv = 0, __ru_msgrcv_word = 0}, {ru_nsignals = 0, __ru_nsignals_word = 0}, {ru_nvcsw = 0, __ru_nvcsw_word = 0}, { ru_nivcsw = 0, __ru_nivcsw_word = 0}}}} (gdb) ``` 为每一列(c1&c2)准备SortSupport数据(分配内存空间) ``` (gdb) n 850 SortSupport sortKey = state->sortKeys + i; (gdb) 852 AssertArg(attNums[i] != 0); (gdb) p *state->sortKeys $10 = {ssup_cxt = 0x0, ssup_collation = 0, ssup_reverse = false, ssup_nulls_first = false, ssup_attno = 0, ssup_extra = 0x0, comparator = 0x0, abbreviate = false, abbrev_converter = 0x0, abbrev_abort = 0x0, abbrev_full_comparator = 0x0} (gdb) n 853 AssertArg(sortOperators[i] != 0); (gdb) 855 sortKey->ssup_cxt = CurrentMemoryContext; (gdb) 856 sortKey->ssup_collation = sortCollations[i]; (gdb) 857 sortKey->ssup_nulls_first = nullsFirstFlags[i]; (gdb) 858 sortKey->ssup_attno = attNums[i]; (gdb) 860 sortKey->abbreviate = (i == 0); (gdb) 862 PrepareSortSupportFromOrderingOp(sortOperators[i], sortKey); (gdb) 848 for (i = 0; i < nkeys; i++) (gdb) 850 SortSupport sortKey = state->sortKeys + i; (gdb) 852 AssertArg(attNums[i] != 0); (gdb) 853 AssertArg(sortOperators[i] != 0); (gdb) 855 sortKey->ssup_cxt = CurrentMemoryContext; (gdb) 856 sortKey->ssup_collation = sortCollations[i]; (gdb) 857 sortKey->ssup_nulls_first = nullsFirstFlags[i]; (gdb) 858 sortKey->ssup_attno = attNums[i]; (gdb) 860 sortKey->abbreviate = (i == 0); (gdb) 862 PrepareSortSupportFromOrderingOp(sortOperators[i], sortKey); (gdb) 848 for (i = 0; i < nkeys; i++) (gdb) ``` 完成初始化,返回state ``` (gdb) 871 if (nkeys == 1 && !state->sortKeys->abbrev_converter) (gdb) n 874 MemoryContextSwitchTo(oldcontext); (gdb) 876 return state; (gdb) p *state $11 = {status = TSS_INITIAL, nKeys = 2, randomAccess = false, bounded = false, boundUsed = false, bound = 0, tuples = true, availMem = 4169704, allowedMem = 4194304, maxTapes = 0, tapeRange = 0, sortcontext = 0x2093290, tuplecontext = 0x20992c0, tapeset = 0x0, comparetup = 0xa7525b <comparetup_heap>, copytup = 0xa76247 <copytup_heap>, writetup = 0xa76de1 <writetup_heap>, readtup = 0xa76ec6 <readtup_heap>, memtuples = 0x209b310, memtupcount = 0, memtupsize = 1024, growmemtuples = true, slabAllocatorUsed = false, slabMemoryBegin = 0x0, slabMemoryEnd = 0x0, slabFreeHead = 0x0, read_buffer_size = 0, lastReturnedTuple = 0x0, currentRun = 0, mergeactive = 0x0, Level = 0, destTape = 0, tp_fib = 0x0, tp_runs = 0x0, tp_dummy = 0x0, tp_tapenum = 0x0, activeTapes = 0, result_tape = -1, current = 0, eof_reached = false, markpos_block = 0, markpos_offset = 0, markpos_eof = false, worker = -1, shared = 0x0, nParticipants = -1, tupDesc = 0x208fa40, sortKeys = 0x20937c0, onlyKey = 0x0, abbrevNext = 10, indexInfo = 0x0, estate = 0x0, heapRel = 0x0, indexRel = 0x0, enforceUnique = false, high_mask = 0, low_mask = 0, max_buckets = 0, datumType = 0, datumTypeLen = 0, ru_start = {tv = {tv_sec = 0, tv_usec = 0}, ru = {ru_utime = {tv_sec = 0, tv_usec = 0}, ru_stime = {tv_sec = 0, tv_usec = 0}, {ru_maxrss = 0, __ru_maxrss_word = 0}, {ru_ixrss = 0, __ru_ixrss_word = 0}, { ru_idrss = 0, __ru_idrss_word = 0}, {ru_isrss = 0, __ru_isrss_word = 0}, {ru_minflt = 0, __ru_minflt_word = 0}, { ru_majflt = 0, __ru_majflt_word = 0}, {ru_nswap = 0, __ru_nswap_word = 0}, {ru_inblock = 0, __ru_inblock_word = 0}, {ru_oublock = 0, __ru_oublock_word = 0}, {ru_msgsnd = 0, __ru_msgsnd_word = 0}, {ru_msgrcv = 0, __ru_msgrcv_word = 0}, {ru_nsignals = 0, __ru_nsignals_word = 0}, {ru_nvcsw = 0, __ru_nvcsw_word = 0}, { ru_nivcsw = 0, __ru_nivcsw_word = 0}}}} (gdb) ``` **tuplesort_puttupleslot** 出现在循环中 ``` for (;;) { //从outer plan中获取元组 slot = ExecProcNode(outerNode); if (TupIsNull(slot)) break;//直至全部获取完毕 //排序 tuplesort_puttupleslot(tuplesortstate, slot); } ``` 以其中一个slot为例说明 ``` (gdb) c Continuing. Breakpoint 2, tuplesort_puttupleslot (state=0x20933a8, slot=0x208f8c8) at tuplesort.c:1436 1436 MemoryContext oldcontext = MemoryContextSwitchTo(state->sortcontext); ``` 输入参数,state为先前调用begin_heap返回的state,slot为outer node返回的元组slot ``` (gdb) p *slot $12 = {type = T_TupleTableSlot, tts_isempty = false, tts_shouldFree = false, tts_shouldFreeMin = false, tts_slow = false, tts_tuple = 0x2090678, tts_tupleDescriptor = 0x7f061a300380, tts_mcxt = 0x208f270, tts_buffer = 103, tts_nvalid = 0, tts_values = 0x208f928, tts_isnull = 0x208f960, tts_mintuple = 0x0, tts_minhdr = {t_len = 0, t_self = {ip_blkid = { bi_hi = 0, bi_lo = 0}, ip_posid = 0}, t_tableOid = 0, t_data = 0x0}, tts_off = 0, tts_fixedTupleDescriptor = true} (gdb) ``` slot中的元组数据 ``` (gdb) p *slot->tts_values $13 = 0 (gdb) p *slot->tts_tuple $14 = {t_len = 56, t_self = {ip_blkid = {bi_hi = 0, bi_lo = 0}, ip_posid = 1}, t_tableOid = 286759, t_data = 0x7f05ee0c4648} (gdb) p *slot->tts_tuple->t_data $15 = {t_choice = {t_heap = {t_xmin = 839, t_xmax = 0, t_field3 = {t_cid = 0, t_xvac = 0}}, t_datum = {datum_len_ = 839, datum_typmod = 0, datum_typeid = 0}}, t_ctid = {ip_blkid = {bi_hi = 0, bi_lo = 0}, ip_posid = 1}, t_infomask2 = 7, t_infomask = 2306, t_hoff = 24 '\030', t_bits = 0x7f05ee0c465f ""} (gdb) p *slot->tts_tuple->t_data->t_bits $16 = 0 '\000' (gdb) x/16ux *slot->tts_tuple->t_data->t_bits 0x0: Cannot access memory at address 0x0 (gdb) x/16ux slot->tts_tuple->t_data->t_bits 0x7f05ee0c465f: 0x5a470b00 0x00003130 0x00000100 0x00000100 0x7f05ee0c466f: 0x00000100 0x00000100 0x00000100 0x00000100 0x7f05ee0c467f: 0x00000000 0x8f282800 0x000000da 0x40023800 0x7f05ee0c468f: 0x04200002 0x00000020 0x709fc800 0x709f9000 (gdb) x/16bx slot->tts_tuple->t_data->t_bits 0x7f05ee0c465f: 0x00 0x0b 0x47 0x5a 0x30 0x31 0x00 0x00 0x7f05ee0c4667: 0x00 0x01 0x00 0x00 0x00 0x01 0x00 0x00 (gdb) x/16bc slot->tts_tuple->t_data->t_bits 0x7f05ee0c465f: 0 '\000' 11 '\v' 71 'G' 90 'Z' 48 '0' 49 '1' 0 '\000' 0 '\000' 0x7f05ee0c4667: 0 '\000' 1 '\001' 0 '\000' 0 '\000' 0 '\000' 1 '\001' 0 '\000' 0 '\000' (gdb) p *slot->tts_tupleDescriptor $17 = {natts = 7, tdtypeid = 286761, tdtypmod = -1, tdhasoid = false, tdrefcount = 2, constr = 0x0, attrs = 0x7f061a3003a0} (gdb) p *slot $18 = {type = T_TupleTableSlot, tts_isempty = false, tts_shouldFree = false, tts_shouldFreeMin = false, tts_slow = false, tts_tuple = 0x2090678, tts_tupleDescriptor = 0x7f061a300380, tts_mcxt = 0x208f270, tts_buffer = 103, tts_nvalid = 0, tts_values = 0x208f928, tts_isnull = 0x208f960, tts_mintuple = 0x0, tts_minhdr = {t_len = 0, t_self = {ip_blkid = { bi_hi = 0, bi_lo = 0}, ip_posid = 0}, t_tableOid = 0, t_data = 0x0}, tts_off = 0, tts_fixedTupleDescriptor = true} (gdb) p *slot->tts_values[0] Cannot access memory at address 0x0 (gdb) p slot->tts_values[0] $19 = 0 (gdb) x/32bc slot->tts_tuple->t_data->t_bits 0x7f05ee0c465f: 0 '\000' 11 '\v' 71 'G' 90 'Z' 48 '0' 49 '1' 0 '\000' 0 '\000' 0x7f05ee0c4667: 0 '\000' 1 '\001' 0 '\000' 0 '\000' 0 '\000' 1 '\001' 0 '\000' 0 '\000' 0x7f05ee0c466f: 0 '\000' 1 '\001' 0 '\000' 0 '\000' 0 '\000' 1 '\001' 0 '\000' 0 '\000' 0x7f05ee0c4677: 0 '\000' 1 '\001' 0 '\000' 0 '\000' 0 '\000' 1 '\001' 0 '\000' 0 '\000' (gdb) x/32bx slot->tts_tuple->t_data->t_bits 0x7f05ee0c465f: 0x00 0x0b 0x47 0x5a 0x30 0x31 0x00 0x00 0x7f05ee0c4667: 0x00 0x01 0x00 0x00 0x00 0x01 0x00 0x00 0x7f05ee0c466f: 0x00 0x01 0x00 0x00 0x00 0x01 0x00 0x00 0x7f05ee0c4677: 0x00 0x01 0x00 0x00 0x00 0x01 0x00 0x00 ``` 拷贝元组,并放到state->memtuples中 ``` (gdb) n 1443 COPYTUP(state, &stup, (void *) slot); (gdb) 1445 puttuple_common(state, &stup); (gdb) step puttuple_common (state=0x20933a8, tuple=0x7ffe890e0b00) at tuplesort.c:1639 1639 Assert(!LEADER(state)); (gdb) n 1641 switch (state->status) (gdb) p state->status $20 = TSS_INITIAL (gdb) n 1652 if (state->memtupcount >= state->memtupsize - 1) (gdb) p state->memtupcount $21 = 0 (gdb) p state->memtupsize - 1 $22 = 1023 (gdb) n 1657 state->memtuples[state->memtupcount++] = *tuple; (gdb) 1671 if (state->bounded && (gdb) p state->bounded $23 = false (gdb) n 1688 if (state->memtupcount < state->memtupsize && !LACKMEM(state)) (gdb) 1689 return; (gdb) 1743 } (gdb) tuplesort_puttupleslot (state=0x20933a8, slot=0x208f8c8) at tuplesort.c:1447 1447 MemoryContextSwitchTo(oldcontext); (gdb) 1448 } (gdb) (gdb) p state->memtuples[0] $25 = {tuple = 0x20993d8, datum1 = 1, isnull1 = false, tupindex = 0} ``` **tuplesort_performsort** ``` (gdb) info b Num Type Disp Enb Address What 1 breakpoint keep y 0x0000000000a6ffa1 in tuplesort_begin_heap at tuplesort.c:812 breakpoint already hit 1 time 2 breakpoint keep y 0x0000000000a7119d in tuplesort_puttupleslot at tuplesort.c:1436 breakpoint already hit 1 time 3 breakpoint keep y 0x0000000000a71f45 in tuplesort_performsort at tuplesort.c:1792 (gdb) del 2 (gdb) c Continuing. Breakpoint 3, tuplesort_performsort (state=0x20933a8) at tuplesort.c:1792 1792 MemoryContext oldcontext = MemoryContextSwitchTo(state->sortcontext); (gdb) ``` 输入参数 ``` (gdb) p *state $27 = {status = TSS_BUILDRUNS, nKeys = 2, randomAccess = false, bounded = false, boundUsed = false, bound = 0, tuples = true, availMem = 824360, allowedMem = 4194304, maxTapes = 16, tapeRange = 15, sortcontext = 0x2093290, tuplecontext = 0x20992c0, tapeset = 0x2093a00, comparetup = 0xa7525b <comparetup_heap>, copytup = 0xa76247 <copytup_heap>, writetup = 0xa76de1 <writetup_heap>, readtup = 0xa76ec6 <readtup_heap>, memtuples = 0x2611570, memtupcount = 26592, memtupsize = 37448, growmemtuples = false, slabAllocatorUsed = false, slabMemoryBegin = 0x0, slabMemoryEnd = 0x0, slabFreeHead = 0x0, read_buffer_size = 0, lastReturnedTuple = 0x0, currentRun = 2, mergeactive = 0x2093878, Level = 1, destTape = 2, tp_fib = 0x20938a0, tp_runs = 0x20938f8, tp_dummy = 0x2093950, tp_tapenum = 0x20939a8, activeTapes = 0, result_tape = -1, current = 0, eof_reached = false, markpos_block = 0, markpos_offset = 0, markpos_eof = false, worker = -1, shared = 0x0, nParticipants = -1, tupDesc = 0x208fa40, sortKeys = 0x20937c0, onlyKey = 0x0, abbrevNext = 10, indexInfo = 0x0, estate = 0x0, heapRel = 0x0, indexRel = 0x0, enforceUnique = false, high_mask = 0, low_mask = 0, max_buckets = 0, datumType = 0, datumTypeLen = 0, ru_start = {tv = {tv_sec = 0, tv_usec = 0}, ru = {ru_utime = {tv_sec = 0, tv_usec = 0}, ru_stime = {tv_sec = 0, tv_usec = 0}, {ru_maxrss = 0, __ru_maxrss_word = 0}, {ru_ixrss = 0, __ru_ixrss_word = 0}, {ru_idrss = 0, __ru_idrss_word = 0}, {ru_isrss = 0, __ru_isrss_word = 0}, {ru_minflt = 0, __ru_minflt_word = 0}, {ru_majflt = 0, __ru_majflt_word = 0}, {ru_nswap = 0, __ru_nswap_word = 0}, {ru_inblock = 0, __ru_inblock_word = 0}, { ru_oublock = 0, __ru_oublock_word = 0}, {ru_msgsnd = 0, __ru_msgsnd_word = 0}, {ru_msgrcv = 0, __ru_msgrcv_word = 0}, {ru_nsignals = 0, __ru_nsignals_word = 0}, {ru_nvcsw = 0, __ru_nvcsw_word = 0}, { ru_nivcsw = 0, __ru_nivcsw_word = 0}}}} (gdb) p state->memtupsize $28 = 37448 (gdb) ``` state->status状态已切换为TSS_BUILDRUNS ``` (gdb) n 1795 if (trace_sort) (gdb) 1800 switch (state->status) (gdb) p state->status $29 = TSS_BUILDRUNS (gdb) ``` 全部刷到磁盘上,归并排序 ``` (gdb) n 1864 dumptuples(state, true); (gdb) 1865 mergeruns(state); (gdb) 1866 state->eof_reached = false; (gdb) 1867 state->markpos_block = 0L; (gdb) 1868 state->markpos_offset = 0; (gdb) 1869 state->markpos_eof = false; (gdb) 1870 break; (gdb) 1878 if (trace_sort) (gdb) 1890 MemoryContextSwitchTo(oldcontext); (gdb) 1891 } (gdb) ``` DONE! ### 四、参考资料 N/A