本文简单介绍了PG根据查询树生成的执行计划的详细结构，生成执行计划的输入是上一节介绍的查询树Query。
一、PlannedStmt结构
生成执行计划在函数pg_plan_queries中实现,返回的是链表querytree_list,链表中的元素是PlannedStmt.
PlannedStmt结构:
/* ----------------
* PlannedStmt node
*
* The output of the planner is a Plan tree headed by a PlannedStmt node.
* PlannedStmt holds the "one time" information needed by the executor.
*
* For simplicity in APIs, we also wrap utility statements in PlannedStmt
* nodes; in such cases, commandType == CMD_UTILITY, the statement itself
* is in the utilityStmt field, and the rest of the struct is mostly dummy.
* (We do use canSetTag, stmt_location, stmt_len, and possibly queryId.)
* ----------------
*/
typedef struct PlannedStmt
{
NodeTag type;
CmdType commandType; /* select|insert|update|delete|utility */
uint64 queryId; /* query identifier (copied from Query) */
bool hasReturning; /* is it insert|update|delete RETURNING? */
bool hasModifyingCTE; /* has insert|update|delete in WITH? */
bool canSetTag; /* do I set the command result tag? */
bool transientPlan; /* redo plan when TransactionXmin changes? */
bool dependsOnRole; /* is plan specific to current role? */
bool parallelModeNeeded; /* parallel mode required to execute? */
int jitFlags; /* which forms of JIT should be performed */
struct Plan *planTree; /* tree of Plan nodes */
List *rtable; /* list of RangeTblEntry nodes */
/* rtable indexes of target relations for INSERT/UPDATE/DELETE */
List *resultRelations; /* integer list of RT indexes, or NIL */
/*
* rtable indexes of non-leaf target relations for UPDATE/DELETE on all
* the partitioned tables mentioned in the query.
*/
List *nonleafResultRelations;
/*
* rtable indexes of root target relations for UPDATE/DELETE; this list
* maintains a subset of the RT indexes in nonleafResultRelations,
* indicating the roots of the respective partition hierarchies.
*/
List *rootResultRelations;
List *subplans; /* Plan trees for SubPlan expressions; note
* that some could be NULL */
Bitmapset *rewindPlanIDs; /* indices of subplans that require REWIND */
List *rowMarks; /* a list of PlanRowMark's */
List *relationOids; /* OIDs of relations the plan depends on */
List *invalItems; /* other dependencies, as PlanInvalItems */
List *paramExecTypes; /* type OIDs for PARAM_EXEC Params */
Node *utilityStmt; /* non-null if this is utility stmt */
/* statement location in source string (copied from Query) */
int stmt_location; /* start location, or -1 if unknown */
int stmt_len; /* length in bytes; 0 means "rest of string" */
} PlannedStmt;
/* macro for fetching the Plan associated with a SubPlan node */
#define exec_subplan_get_plan(plannedstmt, subplan) \
((Plan *) list_nth((plannedstmt)->subplans, (subplan)->plan_id - 1))
SQL语句:
select t_dwxx.dwmc,t_grxx.grbh,t_grxx.xm,t_jfxx.ny,t_jfxx.je
from t_dwxx,t_grxx,t_jfxx
where t_dwxx.dwbh = t_grxx.dwbh
and t_grxx.grbh = t_jfxx.grbh
and t_dwxx.dwbh IN ('1001','1002')
order by t_grxx.grbh
limit 8;
select * from (
select t_dwxx.dwmc,t_grxx.grbh,t_grxx.xm,t_jfxx.ny,t_jfxx.je
from t_dwxx inner join t_grxx on t_dwxx.dwbh = t_grxx.dwbh
inner join t_jfxx on t_grxx.grbh = t_jfxx.grbh
where t_dwxx.dwbh IN ('1001')
union all
select t_dwxx.dwmc,t_grxx.grbh,t_grxx.xm,t_jfxx.ny,t_jfxx.je
from t_dwxx inner join t_grxx on t_dwxx.dwbh = t_grxx.dwbh
inner join t_jfxx on t_grxx.grbh = t_jfxx.grbh
where t_dwxx.dwbh IN ('1002')
) as ret
order by ret.grbh
limit 4;
跟踪分析:
(gdb) b exec_simple_query
Breakpoint 1 at 0x84cad8: file postgres.c, line 893.
(gdb) c
Continuing.
Breakpoint 1, exec_simple_query (
query_string=0x12b3ef0 "select * from (\nselect t_dwxx.dwmc,t_grxx.grbh,t_grxx.xm,t_jfxx.ny,t_jfxx.je\nfrom t_dwxx inner join t_grxx on t_dwxx.dwbh = t_grxx.dwbh\ninner join t_jfxx on t_grxx.grbh = t_jfxx.grbh\nwhere t_dwxx.dwbh"...) at postgres.c:893
893 CommandDest dest = whereToSendOutput;
1050 plantree_list = pg_plan_queries(querytree_list,
(gdb)
1054 if (snapshot_set)
(gdb) p (PlannedStmt *)plantree_list->head->data.ptr_value
$3 = (PlannedStmt *) 0x7f1a23ea74c8
(gdb) p *(PlannedStmt *)plantree_list->head->data.ptr_value
$4 = {type = T_PlannedStmt, commandType = CMD_SELECT, queryId = 0, hasReturning = false,
hasModifyingCTE = false, canSetTag = true, transientPlan = false, dependsOnRole = false,
parallelModeNeeded = false, jitFlags = 0, planTree = 0x7f1a23ea27f8, rtable = 0x7f1a23ea29b8,
resultRelations = 0x0, nonleafResultRelations = 0x0, rootResultRelations = 0x0, subplans = 0x0,
rewindPlanIDs = 0x0, rowMarks = 0x0, relationOids = 0x7f1a23ea3968, invalItems = 0x0, paramExecTypes = 0x0,
utilityStmt = 0x0, stmt_location = 0, stmt_len = 455}
(gdb) set $pstmt=(PlannedStmt *)plantree_list->head->data.ptr_value
(gdb) p *$pstmt->rtable
$5 = {type = T_List, length = 13, head = 0x7f1a23ea2998, tail = 0x7f1a23ea5cb8}
(gdb) p *(Node *)$pstmt->rtable->head->data.ptr_value
$6 = {type = T_RangeTblEntry}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->data.ptr_value
$7 = {type = T_RangeTblEntry, rtekind = RTE_SUBQUERY, relid = 0, relkind = 0 '\000', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x12d8d40, eref = 0x13abb08, lateral = false, inh = true, inFromCl = true,
requiredPerms = 2, checkAsUser = 0, selectedCols = 0x0, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *((RangeTblEntry *)$pstmt->rtable->head->data.ptr_value)->alias
$8 = {type = T_Alias, aliasname = 0x12d8d28 "ret", colnames = 0x0}
(gdb) p *((RangeTblEntry *)$pstmt->rtable->head->data.ptr_value)->eref
$9 = {type = T_Alias, aliasname = 0x13abb38 "ret", colnames = 0x13abba8}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->next->data.ptr_value
$10 = {type = T_RangeTblEntry, rtekind = RTE_SUBQUERY, relid = 0, relkind = 0 '\000', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x137ee90, eref = 0x137eee0, lateral = false, inh = false, inFromCl = false,
requiredPerms = 0, checkAsUser = 0, selectedCols = 0x0, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *((RangeTblEntry *)$pstmt->rtable->head->next->data.ptr_value)->alias
$11 = {type = T_Alias, aliasname = 0x137eec0 "*SELECT* 1", colnames = 0x0}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->next->next->data.ptr_value
$12 = {type = T_RangeTblEntry, rtekind = RTE_SUBQUERY, relid = 0, relkind = 0 '\000', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x13818d8, eref = 0x1381928, lateral = false, inh = false, inFromCl = false,
requiredPerms = 0, checkAsUser = 0, selectedCols = 0x0, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *((RangeTblEntry *)$pstmt->rtable->head->next->next->data.ptr_value)->alias
$13 = {type = T_Alias, aliasname = 0x1381908 "*SELECT* 2", colnames = 0x0}
$14 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26754, relkind = 114 'r', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x0, eref = 0x1384418, lateral = false, inh = false, inFromCl = true,
requiredPerms = 2, checkAsUser = 0, selectedCols = 0x1384598, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->data.ptr_value
$15 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26757, relkind = 114 'r', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x0, eref = 0x13846e0, lateral = false, inh = false, inFromCl = true,
requiredPerms = 2, checkAsUser = 0, selectedCols = 0x13848b8, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->next->data.ptr_value
$16 = {type = T_RangeTblEntry, rtekind = RTE_JOIN, relid = 0, relkind = 0 '\000', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x0, eref = 0x1384d40, lateral = false, inh = false, inFromCl = true,
requiredPerms = 0, checkAsUser = 0, selectedCols = 0x0, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *((RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->next->data.ptr_value)->eref
$17 = {type = T_Alias, aliasname = 0x1384d70 "unnamed_join", colnames = 0x1384d90}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->next->next->data.ptr_value
$18 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26760, relkind = 114 'r', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x0, eref = 0x1385158, lateral = false, inh = false, inFromCl = true,
requiredPerms = 2, checkAsUser = 0, selectedCols = 0x13852d8, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *((RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->next->next->data.ptr_value)->eref
$19 = {type = T_Alias, aliasname = 0x1385188 "t_jfxx", colnames = 0x13851a0}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->next->next->next->data.ptr_value
$20 = {type = T_RangeTblEntry, rtekind = RTE_JOIN, relid = 0, relkind = 0 '\000', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x0, eref = 0x13858b0, lateral = false, inh = false, inFromCl = true,
requiredPerms = 0, checkAsUser = 0, selectedCols = 0x0, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->next->next->next->next->data.ptr_value
$21 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26754, relkind = 114 'r', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x0, eref = 0x7f1a23e95308, lateral = false, inh = false, inFromCl = true,
requiredPerms = 2, checkAsUser = 0, selectedCols = 0x7f1a23e95458, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *((RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->next->next->next->next->data.ptr_value)->eref
$22 = {type = T_Alias, aliasname = 0x138bf90 "t_dwxx", colnames = 0x7f1a23e95338}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->next->next->next->next->next->data.ptr_value
$23 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26757, relkind = 114 'r', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x0, eref = 0x7f1a23e955a0, lateral = false, inh = false, inFromCl = true,
requiredPerms = 2, checkAsUser = 0, selectedCols = 0x7f1a23e95778, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
(gdb) p *(RangeTblEntry *)$pstmt->rtable->head->next->next->next->next->next->next->next->next->next->data.ptr_value
$24 = {type = T_RangeTblEntry, rtekind = RTE_RELATION, relid = 26757, relkind = 114 'r', tablesample = 0x0,
subquery = 0x0, security_barrier = false, jointype = JOIN_INNER, joinaliasvars = 0x0, functions = 0x0,
funcordinality = false, tablefunc = 0x0, values_lists = 0x0, ctename = 0x0, ctelevelsup = 0,
self_reference = false, coltypes = 0x0, coltypmods = 0x0, colcollations = 0x0, enrname = 0x0,
enrtuples = 0, alias = 0x0, eref = 0x7f1a23e955a0, lateral = false, inh = false, inFromCl = true,
requiredPerms = 2, checkAsUser = 0, selectedCols = 0x7f1a23e95778, insertedCols = 0x0, updatedCols = 0x0,
securityQuals = 0x0}
#--->planTree:Limit
(gdb) p $pstmt->planTree
$25 = (struct Plan *) 0x7f1a23ea27f8
(gdb) p *$pstmt->planTree
$26 = {type = T_Limit, startup_cost = 96.799999999999983, total_cost = 96.809999999999988, plan_rows = 4,
plan_width = 360, parallel_aware = false, parallel_safe = true, plan_node_id = 0,
targetlist = 0x7f1a23ea2d08, qual = 0x0, lefttree = 0x7f1a23ea2488, righttree = 0x0, initPlan = 0x0,
extParam = 0x0, allParam = 0x0}
(gdb) p *$pstmt->relationOids
$45 = {type = T_OidList, length = 6, head = 0x7f1a23ea3948, tail = 0x7f1a23ea5b88}
(gdb) p *$pstmt->relationOids->head
$46 = {data = {ptr_value = 0x6882, int_value = 26754, oid_value = 26754}, next = 0x7f1a23ea3ac8}
#--->planTree->lefttree:Sort
(gdb) p *$pstmt->planTree->lefttree
$52 = {type = T_Sort, startup_cost = 96.799999999999983, total_cost = 96.83499999999998, plan_rows = 14,
plan_width = 360, parallel_aware = false, parallel_safe = true, plan_node_id = 1,
targetlist = 0x7f1a23ea30f8, qual = 0x0, lefttree = 0x7f1a23e9d078, righttree = 0x0, initPlan = 0x0,
extParam = 0x0, allParam = 0x0}
(gdb) p *(Sort *)$pstmt->planTree->lefttree
$53 = {plan = {type = T_Sort, startup_cost = 96.799999999999983, total_cost = 96.83499999999998,
plan_rows = 14, plan_width = 360, parallel_aware = false, parallel_safe = true, plan_node_id = 1,
targetlist = 0x7f1a23ea30f8, qual = 0x0, lefttree = 0x7f1a23e9d078, righttree = 0x0, initPlan = 0x0,
extParam = 0x0, allParam = 0x0}, numCols = 1, sortColIdx = 0x7f1a23e9dae8,
sortOperators = 0x7f1a23ea2440, collations = 0x7f1a23ea2458, nullsFirst = 0x7f1a23ea2470}
(gdb) set $sort=(Sort *)$pstmt->planTree->lefttree
(gdb) p *$sort->plan.lefttree
$59 = {type = T_Append, startup_cost = 16.149999999999999, total_cost = 96.589999999999989, plan_rows = 14,
plan_width = 360, parallel_aware = false, parallel_safe = true, plan_node_id = 2,
targetlist = 0x7f1a23ea34e8, qual = 0x0, lefttree = 0x0, righttree = 0x0, initPlan = 0x0, extParam = 0x0,
allParam = 0x0}
(gdb) p *(Append *)$sort->plan.lefttree
$60 = {plan = {type = T_Append, startup_cost = 16.149999999999999, total_cost = 96.589999999999989,
plan_rows = 14, plan_width = 360, parallel_aware = false, parallel_safe = true, plan_node_id = 2,
targetlist = 0x7f1a23ea34e8, qual = 0x0, lefttree = 0x0, righttree = 0x0, initPlan = 0x0, extParam = 0x0,
allParam = 0x0}, appendplans = 0x7f1a23ea1030, first_partial_plan = 2, partitioned_rels = 0x0,
part_prune_infos = 0x0}
##--->planTree->lefttree->plan.lefttree:Append
(gdb)set $append=(Append *)$sort->plan.lefttree
(gdb) p *$append.appendplans
$64 = {type = T_List, length = 2, head = 0x7f1a23ea1010, tail = 0x7f1a23ea2420}
(gdb) p *(Node *)$append.appendplans->head->data.ptr_value
$65 = {type = T_NestLoop}
(gdb) p *(NestLoop *)$append.appendplans->head->data.ptr_value
$73 = {join = {plan = {type = T_NestLoop, startup_cost = 16.149999999999999, total_cost = 48.189999999999998,
plan_rows = 7, plan_width = 360, parallel_aware = false, parallel_safe = true, plan_node_id = 4,
targetlist = 0x7f1a23ea3ff8, qual = 0x0, lefttree = 0x7f1a23e9f9a0, righttree = 0x7f1a23ea0e60,
initPlan = 0x0, extParam = 0x0, allParam = 0x0}, jointype = JOIN_INNER, inner_unique = false,
joinqual = 0x0}, nestParams = 0x0}
(gdb) set $nl1=(NestLoop *)$append.appendplans->head->data.ptr_value
(gdb) set $nl2=(NestLoop *)$append.appendplans->head->next->data.ptr_value
(gdb) p *$nl1->join->plan->lefttree
$79 = {type = T_SeqScan, startup_cost = 0, total_cost = 12, plan_rows = 1, plan_width = 256,
parallel_aware = false, parallel_safe = true, plan_node_id = 5, targetlist = 0x7f1a23ea4348,
qual = 0x7f1a23ea46c8, lefttree = 0x0, righttree = 0x0, initPlan = 0x0, extParam = 0x0, allParam = 0x0}
(gdb) p *(SeqScan *)$nl1->join->plan->lefttree
$80 = {plan = {type = T_SeqScan, startup_cost = 0, total_cost = 12, plan_rows = 1, plan_width = 256,
parallel_aware = false, parallel_safe = true, plan_node_id = 5, targetlist = 0x7f1a23ea4348,
qual = 0x7f1a23ea46c8, lefttree = 0x0, righttree = 0x0, initPlan = 0x0, extParam = 0x0, allParam = 0x0},
scanrelid = 4}
(gdb) p *(SeqScan *)$nl1->join->plan->lefttree->qual
$81 = {plan = {type = T_List, startup_cost = 6.9045796748682899e-310, total_cost = 6.9045796748682899e-310,
plan_rows = 0, plan_width = 64, parallel_aware = false, parallel_safe = false, plan_node_id = 19611104,
targetlist = 0x700000067, qual = 0x41300000001, lefttree = 0x640000000e, righttree = 0x700000000,
initPlan = 0xffffffff00000001, extParam = 0x0, allParam = 0x0}, scanrelid = 0}
(gdb) p *(Node *)$nl1->join->plan->lefttree->qual
$82 = {type = T_List}
(gdb) p *(List *)$nl1->join->plan->lefttree->qual
$83 = {type = T_List, length = 1, head = 0x7f1a23ea46a8, tail = 0x7f1a23ea46a8}
(gdb) p *(Node *)$nl1->join->plan->lefttree->qual->head->data.ptr_value
$84 = {type = T_OpExpr}
(gdb) p *(OpExpr *)$nl1->join->plan->lefttree->qual->head->data.ptr_value
$85 = {xpr = {type = T_OpExpr}, opno = 98, opfuncid = 67, opresulttype = 16, opretset = false, opcollid = 0,
inputcollid = 100, args = 0x7f1a23ea4608, location = -1}
(gdb) set $opexpr=(OpExpr *)$nl1->join->plan->lefttree->qual->head->data.ptr_value
(gdb) p *$opexpr->args
$86 = {type = T_List, length = 2, head = 0x7f1a23ea45e8, tail = 0x7f1a23ea4688}
(gdb) p *(Node *)$opexpr->args->head->data.ptr_value
$87 = {type = T_RelabelType}
(gdb) p *(RelabelType *)$opexpr->args->head->data.ptr_value
$88 = {xpr = {type = T_RelabelType}, arg = 0x7f1a23ea4598, resulttype = 25, resulttypmod = -1,
resultcollid = 100, relabelformat = COERCE_IMPLICIT_CAST, location = -1}
(gdb) p *((RelabelType *)$opexpr->args->head->data.ptr_value)->arg
$89 = {type = T_Var}
(gdb) p *(Var *)((RelabelType *)$opexpr->args->head->data.ptr_value)->arg
$90 = {xpr = {type = T_Var}, varno = 4, varattno = 2, vartype = 1043, vartypmod = 14, varcollid = 100,
varlevelsup = 0, varnoold = 4, varoattno = 2, location = 110}
(gdb) p *(RelabelType *)$opexpr->args->tail->data.ptr_value
$91 = {xpr = {type = T_Const}, arg = 0x64ffffffff, resulttype = 4294967295, resulttypmod = 0,
resultcollid = 20488992, relabelformat = COERCE_EXPLICIT_CALL, location = 0}
(gdb) p *(Const *)$opexpr->args->tail->data.ptr_value
$92 = {xpr = {type = T_Const}, consttype = 25, consttypmod = -1, constcollid = 100, constlen = -1,
constvalue = 20488992, constisnull = false, constbyval = false, location = 205}
#其他类似
#DONE!
最终的计划树结构如下:
计划树
二、数据结构
Plan
/* ----------------
* Plan node
*
* All plan nodes "derive" from the Plan structure by having the
* Plan structure as the first field. This ensures that everything works
* when nodes are cast to Plan's. (node pointers are frequently cast to Plan*
* when passed around generically in the executor)
*
* We never actually instantiate any Plan nodes; this is just the common
* abstract superclass for all Plan-type nodes.
* ----------------
*/
typedef struct Plan
{
NodeTag type;
/*
* estimated execution costs for plan (see costsize.c for more info)
*/
Cost startup_cost; /* cost expended before fetching any tuples */
Cost total_cost; /* total cost (assuming all tuples fetched) */
/*
* planner's estimate of result size of this plan step
*/
double plan_rows; /* number of rows plan is expected to emit */
int plan_width; /* average row width in bytes */
/*
* information needed for parallel query
*/
bool parallel_aware; /* engage parallel-aware logic? */
bool parallel_safe; /* OK to use as part of parallel plan? */
/*
* Common structural data for all Plan types.
*/
int plan_node_id; /* unique across entire final plan tree */
List *targetlist; /* target list to be computed at this node */
List *qual; /* implicitly-ANDed qual conditions */
struct Plan *lefttree; /* input plan tree(s) */
struct Plan *righttree;
List *initPlan; /* Init Plan nodes (un-correlated expr
* subselects) */
/*
* Information for management of parameter-change-driven rescanning
*
* extParam includes the paramIDs of all external PARAM_EXEC params
* affecting this plan node or its children. setParam params from the
* node's initPlans are not included, but their extParams are.
*
* allParam includes all the extParam paramIDs, plus the IDs of local
* params that affect the node (i.e., the setParams of its initplans).
* These are _all_ the PARAM_EXEC params that affect this node.
*/
Bitmapset *extParam;
Bitmapset *allParam;
} Plan;
Limit
/* ----------------
* limit node
*
* Note: as of Postgres 8.2, the offset and count expressions are expected
* to yield int8, rather than int4 as before.
* ----------------
*/
typedef struct Limit
{
Plan plan;
Node *limitOffset; /* OFFSET parameter, or NULL if none */
Node *limitCount; /* COUNT parameter, or NULL if none */
} Limit;
Sort
/* ----------------
* sort node
* ----------------
*/
typedef struct Sort
{
Plan plan;
int numCols; /* number of sort-key columns */
AttrNumber *sortColIdx; /* their indexes in the target list */
Oid *sortOperators; /* OIDs of operators to sort them by */
Oid *collations; /* OIDs of collations */
bool *nullsFirst; /* NULLS FIRST/LAST directions */
} Sort;
Append
/* ----------------
* Append node -
* Generate the concatenation of the results of sub-plans.
* ----------------
*/
typedef struct Append
{
Plan plan;
List *appendplans;
/*
* All 'appendplans' preceding this index are non-partial plans. All
* 'appendplans' from this index onwards are partial plans.
*/
int first_partial_plan;
/* RT indexes of non-leaf tables in a partition tree */
List *partitioned_rels;
/* Info for run-time subplan pruning; NULL if we're not doing that */
struct PartitionPruneInfo *part_prune_info;
} Append;
NestLoop
/* ----------------
* nest loop join node
*
* The nestParams list identifies any executor Params that must be passed
* into execution of the inner subplan carrying values from the current row
* of the outer subplan. Currently we restrict these values to be simple
* Vars, but perhaps someday that'd be worth relaxing. (Note: during plan
* creation, the paramval can actually be a PlaceHolderVar expression; but it
* must be a Var with varno OUTER_VAR by the time it gets to the executor.)
* ----------------
*/
typedef struct NestLoop
{
Join join;
List *nestParams; /* list of NestLoopParam nodes */
} NestLoop;
typedef struct NestLoopParam
{
NodeTag type;
int paramno; /* number of the PARAM_EXEC Param to set */
Var *paramval; /* outer-relation Var to assign to Param */
} NestLoopParam;
/*
* ==========
* Join nodes
* ==========
*/
/* ----------------
* merge join node
*
* The expected ordering of each mergeable column is described by a btree
* opfamily OID, a collation OID, a direction (BTLessStrategyNumber or
* BTGreaterStrategyNumber) and a nulls-first flag. Note that the two sides
* of each mergeclause may be of different datatypes, but they are ordered the
* same way according to the common opfamily and collation. The operator in
* each mergeclause must be an equality operator of the indicated opfamily.
* ----------------
*/
typedef struct MergeJoin
{
Join join;
bool skip_mark_restore; /* Can we skip mark/restore calls? */
List *mergeclauses; /* mergeclauses as expression trees */
/* these are arrays, but have the same length as the mergeclauses list: */
Oid *mergeFamilies; /* per-clause OIDs of btree opfamilies */
Oid *mergeCollations; /* per-clause OIDs of collations */
int *mergeStrategies; /* per-clause ordering (ASC or DESC) */
bool *mergeNullsFirst; /* per-clause nulls ordering */
} MergeJoin;
/* ----------------
* hash join node
* ----------------
*/
typedef struct HashJoin
{
Join join;
List *hashclauses;
} HashJoin;
/* ----------------
* Join node
*
* jointype: rule for joining tuples from left and right subtrees
* inner_unique each outer tuple can match to no more than one inner tuple
* joinqual: qual conditions that came from JOIN/ON or JOIN/USING
* (plan.qual contains conditions that came from WHERE)
*
* When jointype is INNER, joinqual and plan.qual are semantically
* interchangeable. For OUTER jointypes, the two are *not* interchangeable;
* only joinqual is used to determine whether a match has been found for
* the purpose of deciding whether to generate null-extended tuples.
* (But plan.qual is still applied before actually returning a tuple.)
* For an outer join, only joinquals are allowed to be used as the merge
* or hash condition of a merge or hash join.
*
* inner_unique is set if the joinquals are such that no more than one inner
* tuple could match any given outer tuple. This allows the executor to
* skip searching for additional matches. (This must be provable from just
* the joinquals, ignoring plan.qual, due to where the executor tests it.)
* ----------------
*/
typedef struct Join
{
Plan plan;
JoinType jointype;
bool inner_unique;
List *joinqual; /* JOIN quals (in addition to plan.qual) */
} Join;
SeqScan
/*
* ==========
* Scan nodes
* ==========
*/
typedef struct Scan
{
Plan plan;
Index scanrelid; /* relid is index into the range table */
} Scan;
/* ----------------
* sequential scan node
* ----------------
*/
typedef Scan SeqScan;
三、小结
1、PlannedStmt：这是已规划的SQL语句，可用于Executor执行；
2、重要的数据结构：计划的基础结构Plan，“继承“的结构Limit、Sort等。
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