小编给大家分享一下PostgreSQL中结合实际的内存数据介绍相关数据结构，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！
一、数据结构
typedef struct EquivalenceClass
{
NodeTag type;
List *ec_opfamilies;
Oid ec_collation;
List *ec_members;
List *ec_sources;
List *ec_derives;
Relids ec_relids;
bool ec_has_const;
bool ec_has_volatile;
bool ec_below_outer_join;
bool ec_broken;
Index ec_sortref;
Index ec_min_security;
Index ec_max_security;
struct EquivalenceClass *ec_merged;
} EquivalenceClass;
#define EC_MUST_BE_REDUNDANT(eclass) \
((eclass)->ec_has_const && !(eclass)->ec_below_outer_join)
typedef struct EquivalenceMember
{
NodeTag type;
Expr *em_expr;
Relids em_relids;
Relids em_nullable_relids;
bool em_is_const;
bool em_is_child;
Oid em_datatype;
} EquivalenceMember;二、跟踪分析
启动gdb,跟踪:
(gdb) b query_planner
Breakpoint 3 at 0x7693b5: file planmain.c, line 57.执行函数deconstruct_jointree,查看root结构
156 joinlist = deconstruct_jointree(root);
(gdb)
163 reconsider_outer_join_clauses(root);
(gdb) p *root
$4 = {type = T_PlannerInfo, parse = 0x2c53ad0, glob = 0x2c8bff8, query_level = 1, parent_root = 0x0, plan_params = 0x0,
outer_params = 0x0, simple_rel_array = 0x2c941f8, simple_rel_array_size = 6, simple_rte_array = 0x2c94248,
all_baserels = 0x0, nullable_baserels = 0x0, join_rel_list = 0x0, join_rel_hash = 0x0, join_rel_level = 0x0,
join_cur_level = 0, init_plans = 0x0, cte_plan_ids = 0x0, multiexpr_params = 0x0, eq_classes = 0x2c960b8,
canon_pathkeys = 0x0, left_join_clauses = 0x0, right_join_clauses = 0x0, full_join_clauses = 0x0, join_info_list = 0x0,
append_rel_list = 0x0, rowMarks = 0x0, placeholder_list = 0x0, fkey_list = 0x0, query_pathkeys = 0x0,
group_pathkeys = 0x0, window_pathkeys = 0x0, distinct_pathkeys = 0x0, sort_pathkeys = 0x0, part_schemes = 0x0,
initial_rels = 0x0, upper_rels = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}, upper_targets = {0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0}, processed_tlist = 0x2c8e3d0, grouping_map = 0x0, minmax_aggs = 0x0, planner_cxt = 0x2b9fde0,
total_table_pages = 0, tuple_fraction = 0, limit_tuples = -1, qual_security_level = 0, inhTargetKind = INHKIND_NONE,
hasJoinRTEs = true, hasLateralRTEs = true, hasDeletedRTEs = false, hasHavingQual = false, hasPseudoConstantQuals = false,
hasRecursion = false, wt_param_id = -1, non_recursive_path = 0x0, curOuterRels = 0x0, curOuterParams = 0x0,
join_search_private = 0x0, partColsUpdated = false}root->eq_classes是等价类链表,其中的元素是等价类
(gdb) p *root->eq_classes
$1 = {type = T_List, length = 2, head = 0x2c6daf8, tail = 0x2c6ddf8}
(gdb) set $ec1=(EquivalenceClass *)root->eq_classes->head->data.ptr_value
(gdb) set $ec2=(EquivalenceClass *)root->eq_classes->head->next->data.ptr_value
(gdb) p *$ec1
$4 = {type = T_EquivalenceClass, ec_opfamilies = 0x2c6d980, ec_collation = 100, ec_members = 0x2c6da58,
ec_sources = 0x2c6d9f0, ec_derives = 0x0, ec_relids = 0x2c6da20, ec_has_const = false, ec_has_volatile = false,
ec_below_outer_join = false, ec_broken = false, ec_sortref = 0, ec_min_security = 0, ec_max_security = 0, ec_merged = 0x0}
(gdb) p *$ec2
$5 = {type = T_EquivalenceClass, ec_opfamilies = 0x2c6dc30, ec_collation = 100, ec_members = 0x2c6dd58,
ec_sources = 0x2c6dca0, ec_derives = 0x0, ec_relids = 0x2c6dd20, ec_has_const = true, ec_has_volatile = false,
ec_below_outer_join = false, ec_broken = false, ec_sortref = 0, ec_min_security = 0, ec_max_security = 0, ec_merged = 0x0}
(gdb)第1个等价类信息
ec_opfamilies
(gdb) p *$ec1->ec_opfamilies
$6 = {type = T_OidList, length = 2, head = 0x2c6d960, tail = 0x2c6d9b0}
(gdb) p $ec1->ec_opfamilies->head->data.oid_value
$7 = 1994
(gdb) p $ec1->ec_opfamilies->head->next->data.oid_value
$8 = 2095
(gdb)数据字典中相应的记录:
testdb=# select * from pg_opfamily where oid=2095;
opfmethod | opfname | opfnamespace | opfowner
-----------+------------------+--------------+----------
403 | text_pattern_ops | 11 | 10
(1 row)
testdb=# select * from pg_opfamily where oid=1994;
opfmethod | opfname | opfnamespace | opfowner
-----------+----------+--------------+----------
403 | text_ops | 11 | 10
(1 row)ec_members,共有2个元素
第1个元素,是rtindex=3的RTE,属性编号为2的字段,即t_grxx.grbh
(gdb) p *$ec1->ec_members
$10 = {type = T_List, length = 2, head = 0x2c6da38, tail = 0x2c6dad8}
(gdb) set $ec1_em1=(EquivalenceMember *)$ec1->ec_members->head->data.ptr_value
(gdb) set $ec1_em2=(EquivalenceMember *)$ec1->ec_members->head->next->data.ptr_value
(gdb) p *$ec1_em1
$13 = {type = T_EquivalenceMember, em_expr = 0x2c69f88, em_relids = 0x2c6d770, em_nullable_relids = 0x0,
em_is_const = false, em_is_child = false, em_datatype = 25}
(gdb) p *$ec1_em1
$13 = {type = T_EquivalenceMember, em_expr = 0x2c69f88, em_relids = 0x2c6d770, em_nullable_relids = 0x0,
em_is_const = false, em_is_child = false, em_datatype = 25}
(gdb) p *$ec1_em1->em_expr
$14 = {type = T_RelabelType}
(gdb) p *(RelabelType *)$ec1_em1->em_expr
$15 = {xpr = {type = T_RelabelType}, arg = 0x2c69f38, resulttype = 25, resulttypmod = -1, resultcollid = 100,
relabelformat = COERCE_IMPLICIT_CAST, location = -1}
(gdb) p *((RelabelType *)$ec1_em1->em_expr)->arg
$16 = {type = T_Var}
(gdb) p *(Var *)((RelabelType *)$ec1_em1->em_expr)->arg
$17 = {xpr = {type = T_Var}, varno = 3, varattno = 2, vartype = 1043, vartypmod = 14, varcollid = 100, varlevelsup = 0,
varnoold = 3, varoattno = 2, location = 136}第2个元素,是rtindex=4的RTE,属性编号为1的字段,即t_jfxx.grbh
(gdb) p *$ec1_em2->em_expr
$28 = {type = T_RelabelType}
(gdb) p *(RelabelType *)$ec1_em2->em_expr
$29 = {xpr = {type = T_RelabelType}, arg = 0x2c69fd8, resulttype = 25, resulttypmod = -1, resultcollid = 100,
relabelformat = COERCE_IMPLICIT_CAST, location = -1}
(gdb) p *((RelabelType *)$ec1_em2->em_expr)->arg
$30 = {type = T_Var}
(gdb) p *(Var *)((RelabelType *)$ec1_em2->em_expr)->arg
$31 = {xpr = {type = T_Var}, varno = 4, varattno = 1, vartype = 1043, vartypmod = 14, varcollid = 100, varlevelsup = 0,
varnoold = 4, varoattno = 1, location = 146}其他信息
(gdb) p *$ec1->ec_sources
$34 = {type = T_List, length = 1, head = 0x2c6d9d0, tail = 0x2c6d9d0}
(gdb) p *(Node *)$ec1->ec_sources->head->data.ptr_value
$35 = {type = T_RestrictInfo}
(gdb) p *(RestrictInfo *)$ec1->ec_sources->head->data.ptr_value
$36 = {type = T_RestrictInfo, clause = 0x2c6a098, is_pushed_down = true, outerjoin_delayed = false, can_join = true,
pseudoconstant = false, leakproof = false, security_level = 0, clause_relids = 0x2c6d7a0, required_relids = 0x2c6d758,
outer_relids = 0x0, nullable_relids = 0x0, left_relids = 0x2c6d770, right_relids = 0x2c6d788, orclause = 0x0,
parent_ec = 0x0, eval_cost = {startup = -1, per_tuple = 0}, norm_selec = -1, outer_selec = -1,
mergeopfamilies = 0x2c6d980, left_ec = 0x2c6ce68, right_ec = 0x2c6ce68, left_em = 0x2c6d890, right_em = 0x2c6da88,
scansel_cache = 0x0, outer_is_left = false, hashjoinoperator = 0, left_bucketsize = -1, right_bucketsize = -1,
left_mcvfreq = -1, right_mcvfreq = -1}
(gdb) p *$ec1->ec_relids
$38 = {nwords = 1, words = 0x2c6da24}
#即3号和4号RTE
(gdb) p $ec1->ec_relids->words[0]
$39 = 24第2个等价类信息
(gdb) p *$ec2
$41 = {type = T_EquivalenceClass, ec_opfamilies = 0x2c6dc30, ec_collation = 100, ec_members = 0x2c6dd58,
ec_sources = 0x2c6dca0, ec_derives = 0x0, ec_relids = 0x2c6dd20, ec_has_const = true, ec_has_volatile = false,
ec_below_outer_join = false, ec_broken = false, ec_sortref = 0, ec_min_security = 0, ec_max_security = 0, ec_merged = 0x0}ec_opfamilies,与第1个等价类的信息一致
(gdb) p *$ec2->ec_opfamilies
$42 = {type = T_OidList, length = 2, head = 0x2c6dc60, tail = 0x2c6dc10}
(gdb) p $ec2->ec_opfamilies->head->data.oid_value
$43 = 1994
(gdb) p $ec2->ec_opfamilies->head->next->data.oid_value
$44 = 2095ec_members,有3个元素
(gdb) p *$ec2->ec_members
$46 = {type = T_List, length = 3, head = 0x2c6dd38, tail = 0x2c6df20}
(gdb) set $ec2_em1=(EquivalenceMember *)$ec2->ec_members->head->data.ptr_value
(gdb) set $ec2_em2=(EquivalenceMember *)$ec2->ec_members->head->next->data.ptr_value
(gdb) set $ec2_em3=(EquivalenceMember *)$ec2->ec_members->head->next->next->data.ptr_value第1个元素,3号RTE,属性编号为1的字段,即t_grxx.dwbh
(gdb) p *$ec2_em1
$47 = {type = T_EquivalenceMember, em_expr = 0x2c69d58, em_relids = 0x2c6dbc8, em_nullable_relids = 0x0,
em_is_const = false, em_is_child = false, em_datatype = 25}
(gdb) p *$ec2_em1->em_expr
$48 = {type = T_RelabelType}
(gdb) p *(RelabelType *)$ec2_em1->em_expr
$49 = {xpr = {type = T_RelabelType}, arg = 0x2c69d08, resulttype = 25, resulttypmod = -1, resultcollid = 100,
relabelformat = COERCE_IMPLICIT_CAST, location = -1}
(gdb) p *(Var *)((RelabelType *)$ec2_em1->em_expr)->arg
$50 = {xpr = {type = T_Var}, varno = 3, varattno = 1, vartype = 1043, vartypmod = 14, varcollid = 100, varlevelsup = 0,
varnoold = 3, varoattno = 1, location = 115}第2个元素
(gdb) p *$ec2_em2,1号RTE,属性编号为2的字段,即t_dwxx.dwbh
$52 = {type = T_EquivalenceMember, em_expr = 0x2c69e28, em_relids = 0x2c6dbe0, em_nullable_relids = 0x0,
em_is_const = false, em_is_child = false, em_datatype = 25}
(gdb) p *$ec2_em2->em_expr
$53 = {type = T_RelabelType}
(gdb) p *(Var *)((RelabelType *)$ec2_em2->em_expr)->arg
$54 = {xpr = {type = T_Var}, varno = 1, varattno = 2, vartype = 1043, vartypmod = 14, varcollid = 100, varlevelsup = 0,
varnoold = 1, varoattno = 2, location = 125}第3个元素,是一个常量,即'1001'
(gdb) p *$ec2_em3
$55 = {type = T_EquivalenceMember, em_expr = 0x2c6a498, em_relids = 0x0, em_nullable_relids = 0x0, em_is_const = true,
em_is_child = false, em_datatype = 25}
(gdb) p *$ec2_em3->em_expr
$56 = {type = T_Const}
(gdb) p *((Const *)$ec2_em2->em_expr)->arg
(gdb) p *(Const *)$ec2_em3->em_expr
$58 = {xpr = {type = T_Const}, consttype = 25, consttypmod = -1, constcollid = 100, constlen = -1, constvalue = 46517720,
constisnull = false, constbyval = false, location = 172}看完了这篇文章，相信你对“PostgreSQL中结合实际的内存数据介绍相关数据结构”有了一定的了解，如果想了解更多相关知识，欢迎关注亿速云行业资讯频道，感谢各位的阅读！
