这篇文章主要讲解了“PostgreSQL中hash_inner_and_outer函数分析”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“PostgreSQL中hash_inner_and_outer函数分析”吧！
Cost相关
注意:实际使用的参数值通过系统配置文件定义,而不是这里的常量定义!
typedef double Cost; /* execution cost (in page-access units) */ /* defaults for costsize.c's Cost parameters */ /* NB: cost-estimation code should use the variables, not these constants! */ /* 注意:实际值通过系统配置文件定义,而不是这里的常量定义! */ /* If you change these, update backend/utils/misc/postgresql.sample.conf */ #define DEFAULT_SEQ_PAGE_COST 1.0 //顺序扫描page的成本 #define DEFAULT_RANDOM_PAGE_COST 4.0 //随机扫描page的成本 #define DEFAULT_CPU_TUPLE_COST 0.01 //处理一个元组的CPU成本 #define DEFAULT_CPU_INDEX_TUPLE_COST 0.005 //处理一个索引元组的CPU成本 #define DEFAULT_CPU_OPERATOR_COST 0.0025 //执行一次操作或函数的CPU成本 #define DEFAULT_PARALLEL_TUPLE_COST 0.1 //并行执行,从一个worker传输一个元组到另一个worker的成本 #define DEFAULT_PARALLEL_SETUP_COST 1000.0 //构建并行执行环境的成本 #define DEFAULT_EFFECTIVE_CACHE_SIZE 524288 /*先前已有介绍, measured in pages */ double seq_page_cost = DEFAULT_SEQ_PAGE_COST; double random_page_cost = DEFAULT_RANDOM_PAGE_COST; double cpu_tuple_cost = DEFAULT_CPU_TUPLE_COST; double cpu_index_tuple_cost = DEFAULT_CPU_INDEX_TUPLE_COST; double cpu_operator_cost = DEFAULT_CPU_OPERATOR_COST; double parallel_tuple_cost = DEFAULT_PARALLEL_TUPLE_COST; double parallel_setup_cost = DEFAULT_PARALLEL_SETUP_COST; int effective_cache_size = DEFAULT_EFFECTIVE_CACHE_SIZE; Cost disable_cost = 1.0e10;//1后面10个0,通过设置一个巨大的成本,让优化器自动放弃此路径 int max_parallel_workers_per_gather = 2;//每次gather使用的worker数
hash join的算法实现伪代码如下:
Step 1
FOR small_table_row IN (SELECT * FROM small_table)
LOOP
slot := HASH(small_table_row.join_key);
INSERT_HASH_TABLE(slot,small_table_row);
END LOOP;
Step 2
FOR large_table_row IN (SELECT * FROM large_table) LOOP
slot := HASH(large_table_row.join_key);
small_table_row = LOOKUP_HASH_TABLE(slot,large_table_row.join_key);
IF small_table_row FOUND THEN
output small_table_row + large_table_row;
END IF;
END LOOP;
hash_inner_and_outer
该函数创建hash join访问路径。
//------------------------------------------------ hash_inner_and_outer /* * hash_inner_and_outer * Create hashjoin join paths by explicitly hashing both the outer and * inner keys of each available hash clause. * 通过显式对外表和内表(应用每个可用的hash条件)进行hash操作,创建hash join访问路径 * * 'joinrel' is the join relation * 'outerrel' is the outer join relation * 'innerrel' is the inner join relation * 'jointype' is the type of join to do * 'extra' contains additional input values */ static void hash_inner_and_outer(PlannerInfo *root, RelOptInfo *joinrel, RelOptInfo *outerrel, RelOptInfo *innerrel, JoinType jointype, JoinPathExtraData *extra) { JoinType save_jointype = jointype; bool isouterjoin = IS_OUTER_JOIN(jointype); List *hashclauses; ListCell *l; /* * We need to build only one hashclauses list for any given pair of outer * and inner relations; all of the hashable clauses will be used as keys. * 只需要为给定的外表和内表对构建一个hashclauses条件链表;所有的hashable子句将用作hash键。 * * Scan the join's restrictinfo list to find hashjoinable clauses that are * usable with this pair of sub-relations. * 扫描连接的约束条件restrictinfo链表，找到可用于这对子关系的hash连接hashjoinable子句。 */ hashclauses = NIL; foreach(l, extra->restrictlist) { RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l); /* * If processing an outer join, only use its own join clauses for * hashing. For inner joins we need not be so picky. * 如果处理外连接，则仅使用其自己的连接子句进行哈希操作。对于内连接，则无需如此操作。 */ if (isouterjoin && RINFO_IS_PUSHED_DOWN(restrictinfo, joinrel->relids)) continue; if (!restrictinfo->can_join || restrictinfo->hashjoinoperator == InvalidOid) continue; /* 不能被hash.not hashjoinable */ /* * Check if clause has the form "outer op inner" or "inner op outer". * 检查条件是否有形如outer op inner或者inner op outer的形式 */ if (!clause_sides_match_join(restrictinfo, outerrel, innerrel)) continue; /* no good for these input relations */ hashclauses = lappend(hashclauses, restrictinfo);//加入到hash条件中 } /* If we found any usable hashclauses, make paths */ //如发现可用于hash连接的条件,则构建hash连接访问路径,如无则无法构建 if (hashclauses) { /* * We consider both the cheapest-total-cost and cheapest-startup-cost * outer paths. There's no need to consider any but the * cheapest-total-cost inner path, however. * 外表:既考虑了成本最低的总成本，也考虑了外表启动成本最低的访问路径。 * 内表:除了成本最低的内部路径之外，不需要考虑任何其他路径。 */ Path *cheapest_startup_outer = outerrel->cheapest_startup_path; Path *cheapest_total_outer = outerrel->cheapest_total_path; Path *cheapest_total_inner = innerrel->cheapest_total_path; /* * If either cheapest-total path is parameterized by the other rel, we * can't use a hashjoin. (There's no use looking for alternative * input paths, since these should already be the least-parameterized * available paths.) * 如果其中一个关系参数化了其中一个成本最低的访问路径，那么不能使用hash join。 * (没有必要寻找替代的输入路径，因为这些路径应该已经是参数化最少的可用路径了。) */ if (PATH_PARAM_BY_REL(cheapest_total_outer, innerrel) || PATH_PARAM_BY_REL(cheapest_total_inner, outerrel)) return;//直接退出 /* Unique-ify if need be; we ignore parameterized possibilities */ //如果需要保证唯一性,丢弃参数化 if (jointype == JOIN_UNIQUE_OUTER) { cheapest_total_outer = (Path *) create_unique_path(root, outerrel, cheapest_total_outer, extra->sjinfo); Assert(cheapest_total_outer); jointype = JOIN_INNER; try_hashjoin_path(root, joinrel, cheapest_total_outer, cheapest_total_inner, hashclauses, jointype, extra); /* no possibility of cheap startup here */ } else if (jointype == JOIN_UNIQUE_INNER) { cheapest_total_inner = (Path *) create_unique_path(root, innerrel, cheapest_total_inner, extra->sjinfo); Assert(cheapest_total_inner); jointype = JOIN_INNER; try_hashjoin_path(root, joinrel, cheapest_total_outer, cheapest_total_inner, hashclauses, jointype, extra); if (cheapest_startup_outer != NULL && cheapest_startup_outer != cheapest_total_outer) try_hashjoin_path(root, joinrel, cheapest_startup_outer, cheapest_total_inner, hashclauses, jointype, extra); } else//其他连接类型 { /* * For other jointypes, we consider the cheapest startup outer * together with the cheapest total inner, and then consider * pairings of cheapest-total paths including parameterized ones. * There is no use in generating parameterized paths on the basis * of possibly cheap startup cost, so this is sufficient. * 对于其他连接类型，我们考虑成本最低的的外表启动和内表启动访问路径， * 然后考虑包括参数化路径在内的成本最低的访问路径对。 * 在基于可能较低的启动成本的基础上生成参数化路径是没有用的，上面的做法就足够了。 */ ListCell *lc1; ListCell *lc2; if (cheapest_startup_outer != NULL)//启动成本最低的外表访问路径 try_hashjoin_path(root, joinrel, cheapest_startup_outer, cheapest_total_inner, hashclauses, jointype, extra);//构建hash join访问路径 foreach(lc1, outerrel->cheapest_parameterized_paths)//遍历外表参数化路径 { Path *outerpath = (Path *) lfirst(lc1); /* * We cannot use an outer path that is parameterized by the * inner rel. * 不能使用被内表参数化使用的外表访问路径 */ if (PATH_PARAM_BY_REL(outerpath, innerrel)) continue; foreach(lc2, innerrel->cheapest_parameterized_paths)//遍历内表参数化路径 { Path *innerpath = (Path *) lfirst(lc2); /* * We cannot use an inner path that is parameterized by * the outer rel, either. * 同样的,不能使用被外表参数化使用的内表访问路径 */ if (PATH_PARAM_BY_REL(innerpath, outerrel)) continue; if (outerpath == cheapest_startup_outer && innerpath == cheapest_total_inner) continue; /* already tried it */ try_hashjoin_path(root, joinrel, outerpath, innerpath, hashclauses, jointype, extra);//构建hash连接访问路径 } } } /* * If the joinrel is parallel-safe, we may be able to consider a * partial hash join. However, we can't handle JOIN_UNIQUE_OUTER, * because the outer path will be partial, and therefore we won't be * able to properly guarantee uniqueness. Similarly, we can't handle * JOIN_FULL and JOIN_RIGHT, because they can produce false null * extended rows. Also, the resulting path must not be parameterized. * We would be able to support JOIN_FULL and JOIN_RIGHT for Parallel * Hash, since in that case we're back to a single hash table with a * single set of match bits for each batch, but that will require * figuring out a deadlock-free way to wait for the probe to finish. * 如果连接是并行安全的，可以考虑并行哈希连接。 * 但是，我们不能处理JOIN_UNIQUE_OUTER，因为外部路径是部分的，因此我们不能正确地保证惟一性。 * 类似地，我们不能处理JOIN_FULL和JOIN_RIGHT，因为它们会产生假空扩展行。 * 此外，生成的路径不能被参数化。 * 我们将能够支持JOIN_FULL和JOIN_RIGHT用于并行哈希， * 因为在这种情况下，我们将返回到一个哈希表，每个批处理只有一组匹配位， * 但这需要找到一种没有死锁的方式来等待探测完成。 */ if (joinrel->consider_parallel && save_jointype != JOIN_UNIQUE_OUTER && save_jointype != JOIN_FULL && save_jointype != JOIN_RIGHT && outerrel->partial_pathlist != NIL && bms_is_empty(joinrel->lateral_relids)) { Path *cheapest_partial_outer; Path *cheapest_partial_inner = NULL; Path *cheapest_safe_inner = NULL; cheapest_partial_outer = (Path *) linitial(outerrel->partial_pathlist); /* * Can we use a partial inner plan too, so that we can build a * shared hash table in parallel? * 我们是否也可以使用部分内表访问路径，以便并行构建共享哈希表? */ if (innerrel->partial_pathlist != NIL && enable_parallel_hash) { cheapest_partial_inner = (Path *) linitial(innerrel->partial_pathlist); try_partial_hashjoin_path(root, joinrel, cheapest_partial_outer, cheapest_partial_inner, hashclauses, jointype, extra, true /* parallel_hash */ ); } /* * Normally, given that the joinrel is parallel-safe, the cheapest * total inner path will also be parallel-safe, but if not, we'll * have to search for the cheapest safe, unparameterized inner * path. If doing JOIN_UNIQUE_INNER, we can't use any alternative * inner path. * 通常，假设连接是并行安全的，最便宜的总内表访问路径也是并行安全的， * 但如果不是，我们将不得不寻找成本最低的安全的、非参数化的内表访问路径。 * 如果执行JOIN_UNIQUE_INNER，则不能使用任何替代的内表访问路径。 */ if (cheapest_total_inner->parallel_safe) cheapest_safe_inner = cheapest_total_inner; else if (save_jointype != JOIN_UNIQUE_INNER) cheapest_safe_inner = get_cheapest_parallel_safe_total_inner(innerrel->pathlist); if (cheapest_safe_inner != NULL) try_partial_hashjoin_path(root, joinrel, cheapest_partial_outer, cheapest_safe_inner, hashclauses, jointype, extra, false /* parallel_hash */ ); } } } //----------------------------- try_hashjoin_path /* * try_hashjoin_path * Consider a hash join path; if it appears useful, push it into * the joinrel's pathlist via add_path(). * 尝试构造hash join访问路径. * 如果该访问路径可用,通过add_path函数添加到连接新生成的关系joinrel中的pathlist链表中 */ static void try_hashjoin_path(PlannerInfo *root, RelOptInfo *joinrel, Path *outer_path, Path *inner_path, List *hashclauses, JoinType jointype, JoinPathExtraData *extra) { Relids required_outer; JoinCostWorkspace workspace; /* * Check to see if proposed path is still parameterized, and reject if the * parameterization wouldn't be sensible. * 检查建议的路径是否仍然是参数化的，如果参数化不合理，则拒绝。 * */ required_outer = calc_non_nestloop_required_outer(outer_path, inner_path); if (required_outer && !bms_overlap(required_outer, extra->param_source_rels)) { /* Waste no memory when we reject a path here */ bms_free(required_outer); return; } /* * See comments in try_nestloop_path(). Also note that hashjoin paths * never have any output pathkeys, per comments in create_hashjoin_path. * 参见try_nestloop_path()中的注释。 * 还要注意，hash join访问路径从来没有任何输出路径键，参见create_hashjoin_path中的注释. */ initial_cost_hashjoin(root, &workspace, jointype, hashclauses, outer_path, inner_path, extra, false);//初步估算成本 if (add_path_precheck(joinrel, workspace.startup_cost, workspace.total_cost, NIL, required_outer))//初始判断 { add_path(joinrel, (Path *) create_hashjoin_path(root, joinrel, jointype, &workspace, extra, outer_path, inner_path, false, /* parallel_hash */ extra->restrictlist, required_outer, hashclauses));//创建hash join访问路径,并添加 } else { /* Waste no memory when we reject a path here */ bms_free(required_outer); } } //------------------ create_hashjoin_path /* * create_hashjoin_path * Creates a pathnode corresponding to a hash join between two relations. * 创建hash join访问路径Node * * 'joinrel' is the join relation * 'jointype' is the type of join required * 'workspace' is the result from initial_cost_hashjoin * 'extra' contains various information about the join * 'outer_path' is the cheapest outer path * 'inner_path' is the cheapest inner path * 'parallel_hash' to select Parallel Hash of inner path (shared hash table) * 'restrict_clauses' are the RestrictInfo nodes to apply at the join * 'required_outer' is the set of required outer rels * 'hashclauses' are the RestrictInfo nodes to use as hash clauses * (this should be a subset of the restrict_clauses list) */ HashPath * create_hashjoin_path(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype, JoinCostWorkspace *workspace, JoinPathExtraData *extra, Path *outer_path, Path *inner_path, bool parallel_hash, List *restrict_clauses, Relids required_outer, List *hashclauses) { HashPath *pathnode = makeNode(HashPath); pathnode->jpath.path.pathtype = T_HashJoin; pathnode->jpath.path.parent = joinrel; pathnode->jpath.path.pathtarget = joinrel->reltarget; pathnode->jpath.path.param_info = get_joinrel_parampathinfo(root, joinrel, outer_path, inner_path, extra->sjinfo, required_outer, &restrict_clauses); pathnode->jpath.path.parallel_aware = joinrel->consider_parallel && parallel_hash; pathnode->jpath.path.parallel_safe = joinrel->consider_parallel && outer_path->parallel_safe && inner_path->parallel_safe; /* This is a foolish way to estimate parallel_workers, but for now... */ pathnode->jpath.path.parallel_workers = outer_path->parallel_workers; /* * A hashjoin never has pathkeys, since its output ordering is * unpredictable due to possible batching. XXX If the inner relation is * small enough, we could instruct the executor that it must not batch, * and then we could assume that the output inherits the outer relation's * ordering, which might save a sort step. However there is considerable * downside if our estimate of the inner relation size is badly off. For * the moment we don't risk it. (Note also that if we wanted to take this * seriously, joinpath.c would have to consider many more paths for the * outer rel than it does now.) * hashjoin从来没有路径键，因为由于可能的批处理，其输出顺序不可预测。 * 如果内部关系足够小，可以指示执行器它不执行批处理，然后可以假设输出继承外部关系的顺序，这样可以节省排序步骤。 * 然而，如果对内部关系大小的估计严重不足，就会有相当大的负面影响。 * (还要注意，如果我们想认真对待这个问题，那就是joinpath.c将不得不考虑比现在更多的外表访问路径。) */ pathnode->jpath.path.pathkeys = NIL; pathnode->jpath.jointype = jointype; pathnode->jpath.inner_unique = extra->inner_unique; pathnode->jpath.outerjoinpath = outer_path; pathnode->jpath.innerjoinpath = inner_path; pathnode->jpath.joinrestrictinfo = restrict_clauses; pathnode->path_hashclauses = hashclauses; /* final_cost_hashjoin will fill in pathnode->num_batches */ final_cost_hashjoin(root, pathnode, workspace, extra);//最终的成本估算 return pathnode; }测试脚本如下
testdb=# explain verbose select dw.*,grjf.grbh,grjf.xm,grjf.ny,grjf.je testdb-# from t_dwxx dw,lateral (select gr.grbh,gr.xm,jf.ny,jf.je testdb(# from t_grxx gr inner join t_jfxx jf testdb(# on gr.dwbh = dw.dwbh testdb(# and gr.grbh = jf.grbh) grjf testdb-# order by dw.dwbh; QUERY PLAN ------------------------------------------------------------------------------------------------- Sort (cost=20070.93..20320.93 rows=100000 width=47) Output: dw.dwmc, dw.dwbh, dw.dwdz, gr.grbh, gr.xm, jf.ny, jf.je Sort Key: dw.dwbh -> Hash Join (cost=3754.00..8689.61 rows=100000 width=47) Output: dw.dwmc, dw.dwbh, dw.dwdz, gr.grbh, gr.xm, jf.ny, jf.je Inner Unique: true Hash Cond: ((gr.dwbh)::text = (dw.dwbh)::text) -> Hash Join (cost=3465.00..8138.00 rows=100000 width=31) Output: gr.grbh, gr.xm, gr.dwbh, jf.ny, jf.je Hash Cond: ((jf.grbh)::text = (gr.grbh)::text) -> Seq Scan on public.t_jfxx jf (cost=0.00..1637.00 rows=100000 width=20) Output: jf.ny, jf.je, jf.grbh -> Hash (cost=1726.00..1726.00 rows=100000 width=16) Output: gr.grbh, gr.xm, gr.dwbh -> Seq Scan on public.t_grxx gr (cost=0.00..1726.00 rows=100000 width=16) Output: gr.grbh, gr.xm, gr.dwbh -> Hash (cost=164.00..164.00 rows=10000 width=20) Output: dw.dwmc, dw.dwbh, dw.dwdz -> Seq Scan on public.t_dwxx dw (cost=0.00..164.00 rows=10000 width=20) Output: dw.dwmc, dw.dwbh, dw.dwdz (20 rows)
启动gdb,设置断点跟踪
(gdb) b hash_inner_and_outer Breakpoint 1 at 0x7b066b: file joinpath.c, line 1684. (gdb) c Continuing. Breakpoint 1, hash_inner_and_outer (root=0x2676078, joinrel=0x26d2bc0, outerrel=0x26814e0, innerrel=0x2682a10, jointype=JOIN_INNER, extra=0x7ffd6ea6b9d0) at joinpath.c:1684 1684 JoinType save_jointype = jointype;
连接类型为JOIN_INNER
(gdb) p jointype $1 = JOIN_INNER
1号和3号RTE的连接(即t_dwxx和t_grxx)
(gdb) p *joinrel->relids->words $3 = 10
开始遍历连接条件,获取hash连接条件
1697 foreach(l, extra->restrictlist) (gdb) 1699 RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
成功获取,t_dwxx.dwbh = t_grxx.dwbh
(gdb) 1697 foreach(l, extra->restrictlist) (gdb) 1722 if (hashclauses) (gdb) p *hashclauses $4 = {type = T_List, length = 1, head = 0x26d4068, tail = 0x26d4068}获取成本最低的外表启动路径/成本最低的外表访问路径/成本最低的内部访问路径
分别是外表顺序扫描/外表顺序扫描/内部顺序扫描
(gdb) n 1729 Path *cheapest_startup_outer = outerrel->cheapest_startup_path; (gdb) 1730 Path *cheapest_total_outer = outerrel->cheapest_total_path; (gdb) 1731 Path *cheapest_total_inner = innerrel->cheapest_total_path; (gdb) p *cheapest_startup_outer $5 = {type = T_Path, pathtype = T_SeqScan, parent = 0x26814e0, pathtarget = 0x2681718, param_info = 0x0, parallel_aware = false, parallel_safe = true, parallel_workers = 0, rows = 10000, startup_cost = 0, total_cost = 164, pathkeys = 0x0} (gdb) p *cheapest_total_outer $6 = {type = T_Path, pathtype = T_SeqScan, parent = 0x26814e0, pathtarget = 0x2681718, param_info = 0x0, parallel_aware = false, parallel_safe = true, parallel_workers = 0, rows = 10000, startup_cost = 0, total_cost = 164, pathkeys = 0x0} (gdb) p *cheapest_total_inner $7 = {type = T_Path, pathtype = T_SeqScan, parent = 0x2682a10, pathtarget = 0x2682c48, param_info = 0x0, parallel_aware = false, parallel_safe = true, parallel_workers = 0, rows = 100000, startup_cost = 0, total_cost = 1726, pathkeys = 0x0}如外表成本最低的启动路径不为NULL,则尝试hash连接
(gdb) n 1740 PATH_PARAM_BY_REL(cheapest_total_inner, outerrel)) (gdb) 1739 if (PATH_PARAM_BY_REL(cheapest_total_outer, innerrel) || (gdb) 1744 if (jointype == JOIN_UNIQUE_OUTER) (gdb) 1760 else if (jointype == JOIN_UNIQUE_INNER) (gdb) 1796 if (cheapest_startup_outer != NULL) (gdb) 1797 try_hashjoin_path(root,
进入try_hashjoin_path
(gdb) step try_hashjoin_path (root=0x2676078, joinrel=0x26d2bc0, outer_path=0x26853b8, inner_path=0x26cf610, hashclauses=0x26d4090, jointype=JOIN_INNER, extra=0x7ffd6ea6b9d0) at joinpath.c:737 737 required_outer = calc_non_nestloop_required_outer(outer_path,
try_hashjoin_path->初步估算成本
... 751 initial_cost_hashjoin(root, &workspace, jointype, hashclauses, (gdb) p workspace $9 = {startup_cost = 3465, total_cost = 4261, run_cost = 796, inner_run_cost = 0, inner_rescan_run_cost = 6.9528109284473596e-310, outer_rows = 3.7882102964330281e-317, inner_rows = 2.0115578425988515e-316, outer_skip_rows = 2.0115578425988515e-316, inner_skip_rows = 6.9528109284331305e-310, numbuckets = 131072, numbatches = 2, inner_rows_total = 100000}try_hashjoin_path->进入函数create_hashjoin_path
(gdb) n 759 create_hashjoin_path(root, (gdb) step create_hashjoin_path (root=0x2676078, joinrel=0x26d2bc0, jointype=JOIN_INNER, workspace=0x7ffd6ea6b850, extra=0x7ffd6ea6b9d0, outer_path=0x26853b8, inner_path=0x26cf610, parallel_hash=false, restrict_clauses=0x26d3098, required_outer=0x0, hashclauses=0x26d4090) at pathnode.c:2330 2330 HashPath *pathnode = makeNode(HashPath);
try_hashjoin_path->create_hashjoin_path->计算成本并返回
(gdb) 2370 final_cost_hashjoin(root, pathnode, workspace, extra); (gdb) 2372 return pathnode; (gdb) 2373 } (gdb) p *pathnode $10 = {jpath = {path = {type = T_HashPath, pathtype = T_HashJoin, parent = 0x26d2bc0, pathtarget = 0x26d2df8, param_info = 0x0, parallel_aware = false, parallel_safe = true, parallel_workers = 0, rows = 100000, startup_cost = 3465, total_cost = 5386, pathkeys = 0x0}, jointype = JOIN_INNER, inner_unique = false, outerjoinpath = 0x26853b8, innerjoinpath = 0x26cf610, joinrestrictinfo = 0x26d3098}, path_hashclauses = 0x26d4090, num_batches = 2, inner_rows_total = 100000}try_hashjoin_path->添加路径
(gdb) n try_hashjoin_path (root=0x2676078, joinrel=0x26d2bc0, outer_path=0x26853b8, inner_path=0x26cf610, hashclauses=0x26d4090, jointype=JOIN_INNER, extra=0x7ffd6ea6b9d0) at joinpath.c:758 758 add_path(joinrel, (Path *) (gdb) 776 } (gdb)
回到hash_inner_and_outer,继续循环
(gdb) hash_inner_and_outer (root=0x2676078, joinrel=0x26d2bc0, outerrel=0x26814e0, innerrel=0x2682a10, jointype=JOIN_INNER, extra=0x7ffd6ea6b9d0) at joinpath.c:1805 1805 foreach(lc1, outerrel->cheapest_parameterized_paths)
结束函数调用
1904 } (gdb) add_paths_to_joinrel (root=0x2676078, joinrel=0x26d2bc0, outerrel=0x26814e0, innerrel=0x2682a10, jointype=JOIN_INNER, sjinfo=0x7ffd6ea6bac0, restrictlist=0x26d3098) at joinpath.c:315 315 if (joinrel->fdwroutine && (gdb) p *joinrel->pathlist $11 = {type = T_List, length = 2, head = 0x26d4160, tail = 0x26d3e30}查看joinrel的路径链表
(gdb) p *(Node *)joinrel->pathlist->head->data.ptr_value $12 = {type = T_HashPath} (gdb) p *(Node *)joinrel->pathlist->head->next->data.ptr_value $13 = {type = T_MergePath} (gdb) p *(HashPath *)joinrel->pathlist->head->data.ptr_value $14 = {jpath = {path = {type = T_HashPath, pathtype = T_HashJoin, parent = 0x26d2bc0, pathtarget = 0x26d2df8, param_info = 0x0, parallel_aware = false, parallel_safe = true, parallel_workers = 0, rows = 100000, startup_cost = 3465, total_cost = 5386, pathkeys = 0x0}, jointype = JOIN_INNER, inner_unique = false, outerjoinpath = 0x26853b8, innerjoinpath = 0x26cf610, joinrestrictinfo = 0x26d3098}, path_hashclauses = 0x26d4090, num_batches = 2, inner_rows_total = 100000} (gdb) p *(MergePath *)joinrel->pathlist->head->next->data.ptr_value $15 = {jpath = {path = {type = T_MergePath, pathtype = T_MergeJoin, parent = 0x26d2bc0, pathtarget = 0x26d2df8, param_info = 0x0, parallel_aware = false, parallel_safe = true, parallel_workers = 0, rows = 100000, startup_cost = 10035.66023721841, total_cost = 11955.396048959938, pathkeys = 0x2685928}, jointype = JOIN_INNER, inner_unique = false, outerjoinpath = 0x26ce070, innerjoinpath = 0x26cf610, joinrestrictinfo = 0x26d3098}, path_mergeclauses = 0x26d3eb8, outersortkeys = 0x0, innersortkeys = 0x26d3f18, skip_mark_restore = false, materialize_inner = false}感谢各位的阅读，以上就是“PostgreSQL中hash_inner_and_outer函数分析”的内容了，经过本文的学习后，相信大家对PostgreSQL中hash_inner_and_outer函数分析这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是亿速云，小编将为大家推送更多相关知识点的文章，欢迎关注！
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