PostgreSQL 原始碼解讀（26）- 查詢語句#11（查詢優化-上拉子連結#1）
本文簡單介紹了PG查詢邏輯優化中的子查詢連結(subLink),主要內容包括子連結的基本概念，介紹了主函式以及使用gdb跟蹤分析了上拉函式的部分處理邏輯。
上拉子連結的目的是為了把子連結改寫為半連線或反半連線的方式提升效能。
一、子連結簡介
按官方文件的介紹,子連結Sublink代表的是出現在表示式(可能會出現組合運算子)中的子查詢,子查詢的型別包括:
EXISTS_SUBLINK
語法:EXISTS(SELECT ...)
select *
from t_dwxx a
where exists (select b.dwbh from t_grxx b where a.dwbh = b.dwbh);
ALL_SUBLINK
語法:(lefthand) op ALL (SELECT ...)
select *
from t_dwxx a
where dwbh > all (select b.dwbh from t_grxx b);
ANY_SUBLINK
語法:(lefthand) op ANY (SELECT ...)
select *
from t_dwxx a
where dwbh = any (select b.dwbh from t_grxx b);
ROWCOMPARE_SUBLINK
語法:(lefthand) op (SELECT ...)
select *
from t_dwxx a
where dwbh > (select max(b.dwbh) from t_grxx b);
EXPR_SUBLINK
語法:(SELECT with single targetlist item ...)
select *,(select max(dwbh) from t_grxx)
from t_dwxx a;
MULTIEXPR_SUBLINK
語法:(SELECT with multiple targetlist items ...)
ARRAY_SUBLINK
語法:ARRAY(SELECT with single targetlist item ...)
CTE_SUBLINK
語法:
WITH query (never actually part of an expression)
官方說明:
/*
* SubLink
*
* A SubLink represents a subselect appearing in an expression, and in some
* cases also the combining operator(s) just above it. The subLinkType
* indicates the form of the expression represented:
* EXISTS_SUBLINK EXISTS(SELECT ...)
* ALL_SUBLINK (lefthand) op ALL (SELECT ...)
* ANY_SUBLINK (lefthand) op ANY (SELECT ...)
* ROWCOMPARE_SUBLINK (lefthand) op (SELECT ...)
* EXPR_SUBLINK (SELECT with single targetlist item ...)
* MULTIEXPR_SUBLINK (SELECT with multiple targetlist items ...)
* ARRAY_SUBLINK ARRAY(SELECT with single targetlist item ...)
* CTE_SUBLINK WITH query (never actually part of an expression)
* For ALL, ANY, and ROWCOMPARE, the lefthand is a list of expressions of the
* same length as the subselect's targetlist. ROWCOMPARE will *always* have
* a list with more than one entry; if the subselect has just one target
* then the parser will create an EXPR_SUBLINK instead (and any operator
* above the subselect will be represented separately).
* ROWCOMPARE, EXPR, and MULTIEXPR require the subselect to deliver at most
* one row (if it returns no rows, the result is NULL).
* ALL, ANY, and ROWCOMPARE require the combining operators to deliver boolean
* results. ALL and ANY combine the per-row results using AND and OR
* semantics respectively.
* ARRAY requires just one target column, and creates an array of the target
* column's type using any number of rows resulting from the subselect.
*
* 子連結屬於Expr Node,但並不意味著子連結是可以執行的.子連結必須在計劃期間通過子計劃節點在表示式樹中替換
* SubLink is classed as an Expr node, but it is not actually executable;
* it must be replaced in the expression tree by a SubPlan node during
* planning.
*
* NOTE: in the raw output of gram.y, testexpr contains just the raw form
* of the lefthand expression (if any), and operName is the String name of
* the combining operator. Also, subselect is a raw parsetree. During parse
* analysis, the parser transforms testexpr into a complete boolean expression
* that compares the lefthand value(s) to PARAM_SUBLINK nodes representing the
* output columns of the subselect. And subselect is transformed to a Query.
* This is the representation seen in saved rules and in the rewriter.
*
* In EXISTS, EXPR, MULTIEXPR, and ARRAY SubLinks, testexpr and operName
* are unused and are always null.
*
* subLinkId is currently used only for MULTIEXPR SubLinks, and is zero in
* other SubLinks. This number identifies different multiple-assignment
* subqueries within an UPDATE statement's SET list. It is unique only
* within a particular targetlist. The output column(s) of the MULTIEXPR
* are referenced by PARAM_MULTIEXPR Params appearing elsewhere in the tlist.
*
* The CTE_SUBLINK case never occurs in actual SubLink nodes, but it is used
* in SubPlans generated for WITH subqueries.
*/
typedef enum SubLinkType
{
EXISTS_SUBLINK,
ALL_SUBLINK,
ANY_SUBLINK,
ROWCOMPARE_SUBLINK,
EXPR_SUBLINK,
MULTIEXPR_SUBLINK,
ARRAY_SUBLINK,
CTE_SUBLINK /* for SubPlans only */
} SubLinkType;
typedef struct SubLink
{
Expr xpr;
SubLinkType subLinkType; /* see above */
int subLinkId; /* ID (1..n); 0 if not MULTIEXPR */
Node *testexpr; /* outer-query test for ALL/ANY/ROWCOMPARE */
List *operName; /* originally specified operator name */
Node *subselect; /* subselect as Query* or raw parsetree */
int location; /* token location, or -1 if unknown */
} SubLink;
二、原始碼解讀
standard_planner函式
/*****************************************************************************
*
* Query optimizer entry point
*
* To support loadable plugins that monitor or modify planner behavior,
* we provide a hook variable that lets a plugin get control before and
* after the standard planning process. The plugin would normally call
* standard_planner().
*
* Note to plugin authors: standard_planner() scribbles on its Query input,
* so you'd better copy that data structure if you want to plan more than once.
*
*****************************************************************************/
PlannedStmt *
planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
{
PlannedStmt *result;
if (planner_hook)
result = (*planner_hook) (parse, cursorOptions, boundParams); //鉤子函式,可以實現定製化開發
else
result = standard_planner(parse, cursorOptions, boundParams);//PG的標準實現
return result;
}
/*
輸入引數:
parse-查詢樹
cursorOptions-遊標處理選項,見本節中的資料結構
boundParams-繫結變數?
輸出引數:
*/
PlannedStmt *
standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
{
PlannedStmt *result;//最終結果
PlannerGlobal *glob;//全域性優化資訊
double tuple_fraction;//優化過程中元組的取樣率
PlannerInfo *root;//執行計劃的根節點
RelOptInfo *final_rel;//優化後的Relation資訊
Path *best_path;//最優路徑
Plan *top_plan;//頂層計劃
ListCell *lp,//臨時變數
*lr;
/*
* Set up global state for this planner invocation. This data is needed
* across all levels of sub-Query that might exist in the given command,
* so we keep it in a separate struct that's linked to by each per-Query
* PlannerInfo.
*/
//初始化全域性優化資訊
glob = makeNode(PlannerGlobal);
glob->boundParams = boundParams;
glob->subplans = NIL;
glob->subroots = NIL;
glob->rewindPlanIDs = NULL;
glob->finalrtable = NIL;
glob->finalrowmarks = NIL;
glob->resultRelations = NIL;
glob->nonleafResultRelations = NIL;
glob->rootResultRelations = NIL;
glob->relationOids = NIL;
glob->invalItems = NIL;
glob->paramExecTypes = NIL;
glob->lastPHId = 0;
glob->lastRowMarkId = 0;
glob->lastPlanNodeId = 0;
glob->transientPlan = false;
glob->dependsOnRole = false;
/*
* Assess whether it's feasible to use parallel mode for this query. We
* can't do this in a standalone backend, or if the command will try to
* modify any data, or if this is a cursor operation, or if GUCs are set
* to values that don't permit parallelism, or if parallel-unsafe
* functions are present in the query tree.
*
* (Note that we do allow CREATE TABLE AS, SELECT INTO, and CREATE
* MATERIALIZED VIEW to use parallel plans, but this is safe only because
* the command is writing into a completely new table which workers won't
* be able to see. If the workers could see the table, the fact that
* group locking would cause them to ignore the leader's heavyweight
* relation extension lock and GIN page locks would make this unsafe.
* We'll have to fix that somehow if we want to allow parallel inserts in
* general; updates and deletes have additional problems especially around
* combo CIDs.)
*
* For now, we don't try to use parallel mode if we're running inside a
* parallel worker. We might eventually be able to relax this
* restriction, but for now it seems best not to have parallel workers
* trying to create their own parallel workers.
*
* We can't use parallelism in serializable mode because the predicate
* locking code is not parallel-aware. It's not catastrophic if someone
* tries to run a parallel plan in serializable mode; it just won't get
* any workers and will run serially. But it seems like a good heuristic
* to assume that the same serialization level will be in effect at plan
* time and execution time, so don't generate a parallel plan if we're in
* serializable mode.
*/
//判斷是否可以使用並行模式
//並行是很大的一個話題,有待以後再談
if ((cursorOptions & CURSOR_OPT_PARALLEL_OK) != 0 &&
IsUnderPostmaster &&
parse->commandType == CMD_SELECT &&
!parse->hasModifyingCTE &&
max_parallel_workers_per_gather > 0 &&
!IsParallelWorker() &&
!IsolationIsSerializable())
{
/* all the cheap tests pass, so scan the query tree */
glob->maxParallelHazard = max_parallel_hazard(parse);
glob->parallelModeOK = (glob->maxParallelHazard != PROPARALLEL_UNSAFE);
}
else
{
/* skip the query tree scan, just assume it's unsafe */
glob->maxParallelHazard = PROPARALLEL_UNSAFE;
glob->parallelModeOK = false;
}
/*
* glob->parallelModeNeeded is normally set to false here and changed to
* true during plan creation if a Gather or Gather Merge plan is actually
* created (cf. create_gather_plan, create_gather_merge_plan).
*
* However, if force_parallel_mode = on or force_parallel_mode = regress,
* then we impose parallel mode whenever it's safe to do so, even if the
* final plan doesn't use parallelism. It's not safe to do so if the
* query contains anything parallel-unsafe; parallelModeOK will be false
* in that case. Note that parallelModeOK can't change after this point.
* Otherwise, everything in the query is either parallel-safe or
* parallel-restricted, and in either case it should be OK to impose
* parallel-mode restrictions. If that ends up breaking something, then
* either some function the user included in the query is incorrectly
* labelled as parallel-safe or parallel-restricted when in reality it's
* parallel-unsafe, or else the query planner itself has a bug.
*/
glob->parallelModeNeeded = glob->parallelModeOK &&
(force_parallel_mode != FORCE_PARALLEL_OFF);
/* Determine what fraction of the plan is likely to be scanned */
if (cursorOptions & CURSOR_OPT_FAST_PLAN)//fast-start plan?
{
/*
* We have no real idea how many tuples the user will ultimately FETCH
* from a cursor, but it is often the case that he doesn't want 'em
* all, or would prefer a fast-start plan anyway so that he can
* process some of the tuples sooner. Use a GUC parameter to decide
* what fraction to optimize for.
*/
tuple_fraction = cursor_tuple_fraction;
/*
* We document cursor_tuple_fraction as simply being a fraction, which
* means the edge cases 0 and 1 have to be treated specially here. We
* convert 1 to 0 ("all the tuples") and 0 to a very small fraction.
*/
if (tuple_fraction >= 1.0)
tuple_fraction = 0.0;
else if (tuple_fraction <= 0.0)
tuple_fraction = 1e-10;
}
else
{
/* Default assumption is we need all the tuples */
tuple_fraction = 0.0;
}
//以上:set up for recursive handling of subqueries,為子查詢配置處理器(遞迴方式)
/* primary planning entry point (may recurse for subqueries) */
root = subquery_planner(glob, parse, NULL,
false, tuple_fraction);//進入子查詢優化器
/* Select best Path and turn it into a Plan */
final_rel = fetch_upper_rel(root, UPPERREL_FINAL, NULL);//獲得最上層的優化後的Relation
best_path = get_cheapest_fractional_path(final_rel, tuple_fraction);//獲得最佳路徑
top_plan = create_plan(root, best_path);//建立計劃
/*
* If creating a plan for a scrollable cursor, make sure it can run
* backwards on demand. Add a Material node at the top at need.
*/
if (cursorOptions & CURSOR_OPT_SCROLL)
{
if (!ExecSupportsBackwardScan(top_plan))
top_plan = materialize_finished_plan(top_plan);//如果是Scroll遊標,在前臺執行,那麼物化之(資料不能長期佔用記憶體,但又要滿足Scroll的要求,需要物化至磁碟中)
}
/*
* Optionally add a Gather node for testing purposes, provided this is
* actually a safe thing to do.
*/
if (force_parallel_mode != FORCE_PARALLEL_OFF && top_plan->parallel_safe)//並行執行,新增Gather節點
{
Gather *gather = makeNode(Gather);
/*
* If there are any initPlans attached to the formerly-top plan node,
* move them up to the Gather node; same as we do for Material node in
* materialize_finished_plan.
*/
gather->plan.initPlan = top_plan->initPlan;
top_plan->initPlan = NIL;
gather->plan.targetlist = top_plan->targetlist;
gather->plan.qual = NIL;
gather->plan.lefttree = top_plan;
gather->plan.righttree = NULL;
gather->num_workers = 1;
gather->single_copy = true;
gather->invisible = (force_parallel_mode == FORCE_PARALLEL_REGRESS);
/*
* Since this Gather has no parallel-aware descendants to signal to,
* we don't need a rescan Param.
*/
gather->rescan_param = -1;
/*
* Ideally we'd use cost_gather here, but setting up dummy path data
* to satisfy it doesn't seem much cleaner than knowing what it does.
*/
gather->plan.startup_cost = top_plan->startup_cost +
parallel_setup_cost;
gather->plan.total_cost = top_plan->total_cost +
parallel_setup_cost + parallel_tuple_cost * top_plan->plan_rows;
gather->plan.plan_rows = top_plan->plan_rows;
gather->plan.plan_width = top_plan->plan_width;
gather->plan.parallel_aware = false;
gather->plan.parallel_safe = false;
/* use parallel mode for parallel plans. */
root->glob->parallelModeNeeded = true;
top_plan = &gather->plan;
}
/*
* If any Params were generated, run through the plan tree and compute
* each plan node's extParam/allParam sets. Ideally we'd merge this into
* set_plan_references' tree traversal, but for now it has to be separate
* because we need to visit subplans before not after main plan.
*/
if (glob->paramExecTypes != NIL)
{
Assert(list_length(glob->subplans) == list_length(glob->subroots));
forboth(lp, glob->subplans, lr, glob->subroots)
{
Plan *subplan = (Plan *) lfirst(lp);
PlannerInfo *subroot = lfirst_node(PlannerInfo, lr);
SS_finalize_plan(subroot, subplan);
}
SS_finalize_plan(root, top_plan);
}
/* final cleanup of the plan */
Assert(glob->finalrtable == NIL);
Assert(glob->finalrowmarks == NIL);
Assert(glob->resultRelations == NIL);
Assert(glob->nonleafResultRelations == NIL);
Assert(glob->rootResultRelations == NIL);
top_plan = set_plan_references(root, top_plan);
/* ... and the subplans (both regular subplans and initplans) */
Assert(list_length(glob->subplans) == list_length(glob->subroots));
forboth(lp, glob->subplans, lr, glob->subroots)
{
Plan *subplan = (Plan *) lfirst(lp);
PlannerInfo *subroot = lfirst_node(PlannerInfo, lr);
lfirst(lp) = set_plan_references(subroot, subplan);
}
/* build the PlannedStmt result */
result = makeNode(PlannedStmt);
result->commandType = parse->commandType;
result->queryId = parse->queryId;
result->hasReturning = (parse->returningList != NIL);
result->hasModifyingCTE = parse->hasModifyingCTE;
result->canSetTag = parse->canSetTag;
result->transientPlan = glob->transientPlan;
result->dependsOnRole = glob->dependsOnRole;
result->parallelModeNeeded = glob->parallelModeNeeded;
result->planTree = top_plan;
result->rtable = glob->finalrtable;
result->resultRelations = glob->resultRelations;
result->nonleafResultRelations = glob->nonleafResultRelations;
result->rootResultRelations = glob->rootResultRelations;
result->subplans = glob->subplans;
result->rewindPlanIDs = glob->rewindPlanIDs;
result->rowMarks = glob->finalrowmarks;
result->relationOids = glob->relationOids;
result->invalItems = glob->invalItems;
result->paramExecTypes = glob->paramExecTypes;
/* utilityStmt should be null, but we might as well copy it */
result->utilityStmt = parse->utilityStmt;
result->stmt_location = parse->stmt_location;
result->stmt_len = parse->stmt_len;
result->jitFlags = PGJIT_NONE;
if (jit_enabled && jit_above_cost >= 0 &&
top_plan->total_cost > jit_above_cost)
{
result->jitFlags |= PGJIT_PERFORM;
/*
* Decide how much effort should be put into generating better code.
*/
if (jit_optimize_above_cost >= 0 &&
top_plan->total_cost > jit_optimize_above_cost)
result->jitFlags |= PGJIT_OPT3;
if (jit_inline_above_cost >= 0 &&
top_plan->total_cost > jit_inline_above_cost)
result->jitFlags |= PGJIT_INLINE;
/*
* Decide which operations should be JITed.
*/
if (jit_expressions)
result->jitFlags |= PGJIT_EXPR;
if (jit_tuple_deforming)
result->jitFlags |= PGJIT_DEFORM;
}
return result;
}
subquery_planner
/*--------------------
* subquery_planner
* Invokes the planner on a subquery. We recurse to here for each
* sub-SELECT found in the query tree.
*
* glob is the global state for the current planner run.
* parse is the querytree produced by the parser & rewriter.
* parent_root is the immediate parent Query's info (NULL at the top level).
* hasRecursion is true if this is a recursive WITH query.
* tuple_fraction is the fraction of tuples we expect will be retrieved.
* tuple_fraction is interpreted as explained for grouping_planner, below.
*
* Basically, this routine does the stuff that should only be done once
* per Query object. It then calls grouping_planner. At one time,
* grouping_planner could be invoked recursively on the same Query object;
* that's not currently true, but we keep the separation between the two
* routines anyway, in case we need it again someday.
*
* subquery_planner will be called recursively to handle sub-Query nodes
* found within the query's expressions and rangetable.
*
* Returns the PlannerInfo struct ("root") that contains all data generated
* while planning the subquery. In particular, the Path(s) attached to
* the (UPPERREL_FINAL, NULL) upperrel represent our conclusions about the
* cheapest way(s) to implement the query. The top level will select the
* best Path and pass it through createplan.c to produce a finished Plan.
*--------------------
*/
/*
輸入:
glob-PlannerGlobal
parse-Query結構體指標
parent_root-父PlannerInfo Root節點
hasRecursion-是否遞迴?
tuple_fraction-掃描Tuple比例
輸出:
PlannerInfo指標
*/
PlannerInfo *
subquery_planner(PlannerGlobal *glob, Query *parse,
PlannerInfo *parent_root,
bool hasRecursion, double tuple_fraction)
{
PlannerInfo *root;//返回值
List *newWithCheckOptions;//
List *newHaving;//Having子句
bool hasOuterJoins;//是否存在Outer Join?
RelOptInfo *final_rel;//
ListCell *l;//臨時變數
/* Create a PlannerInfo data structure for this subquery */
root = makeNode(PlannerInfo);//構造返回值
root->parse = parse;
root->glob = glob;
root->query_level = parent_root ? parent_root->query_level + 1 : 1;
root->parent_root = parent_root;
root->plan_params = NIL;
root->outer_params = NULL;
root->planner_cxt = CurrentMemoryContext;
root->init_plans = NIL;
root->cte_plan_ids = NIL;
root->multiexpr_params = NIL;
root->eq_classes = NIL;
root->append_rel_list = NIL;
root->rowMarks = NIL;
memset(root->upper_rels, 0, sizeof(root->upper_rels));
memset(root->upper_targets, 0, sizeof(root->upper_targets));
root->processed_tlist = NIL;
root->grouping_map = NULL;
root->minmax_aggs = NIL;
root->qual_security_level = 0;
root->inhTargetKind = INHKIND_NONE;
root->hasRecursion = hasRecursion;
if (hasRecursion)
root->wt_param_id = SS_assign_special_param(root);
else
root->wt_param_id = -1;
root->non_recursive_path = NULL;
root->partColsUpdated = false;
/*
* If there is a WITH list, process each WITH query and build an initplan
* SubPlan structure for it.
*/
if (parse->cteList)
SS_process_ctes(root);//處理With 語句
/*
* Look for ANY and EXISTS SubLinks in WHERE and JOIN/ON clauses, and try
* to transform them into joins. Note that this step does not descend
* into subqueries; if we pull up any subqueries below, their SubLinks are
* processed just before pulling them up.
*/
if (parse->hasSubLinks)
pull_up_sublinks(root); //上拉子連結
//其他內容...
return root;
}
pull_up_sublinks
下一小節介紹
三、基礎資訊
資料結構/巨集定義
1、cursorOptions
/* ----------------------
* Declare Cursor Statement
*
* The "query" field is initially a raw parse tree, and is converted to a
* Query node during parse analysis. Note that rewriting and planning
* of the query are always postponed until execution.
* ----------------------
*/
#define CURSOR_OPT_BINARY 0x0001 /* BINARY */
#define CURSOR_OPT_SCROLL 0x0002 /* SCROLL explicitly given */
#define CURSOR_OPT_NO_SCROLL 0x0004 /* NO SCROLL explicitly given */
#define CURSOR_OPT_INSENSITIVE 0x0008 /* INSENSITIVE */
#define CURSOR_OPT_HOLD 0x0010 /* WITH HOLD */
/* these planner-control flags do not correspond to any SQL grammar: */
#define CURSOR_OPT_FAST_PLAN 0x0020 /* prefer fast-start plan */
#define CURSOR_OPT_GENERIC_PLAN 0x0040 /* force use of generic plan */
#define CURSOR_OPT_CUSTOM_PLAN 0x0080 /* force use of custom
#define CURSOR_OPT_PARALLEL_OK 0x0100 /* parallel mode OK */
2、Relids
/*
* Relids
* Set of relation identifiers (indexes into the rangetable).
*/
typedef Bitmapset *Relids;
/* The unit size can be adjusted by changing these three declarations: */
#define BITS_PER_BITMAPWORD 32
typedef uint32 bitmapword; /* must be an unsigned type */
typedef int32 signedbitmapword; /* must be the matching signed type */
typedef struct Bitmapset
{
int nwords; /* number of words in array */
bitmapword words[FLEXIBLE_ARRAY_MEMBER]; /* really [nwords] */
} Bitmapset;
四、跟蹤分析
測試指令碼:
testdb=# explain select *
from t_dwxx a
where dwbh > all (select b.dwbh from t_grxx b);
QUERY PLAN
--------------------------------------------------------------------------
Seq Scan on t_dwxx a (cost=0.00..1498.00 rows=80 width=474)
Filter: (SubPlan 1)
SubPlan 1
-> Materialize (cost=0.00..17.35 rows=490 width=38)
-> Seq Scan on t_grxx b (cost=0.00..14.90 rows=490 width=38)
(5 rows)
啟動gdb跟蹤:
(gdb) b pull_up_sublinks
Breakpoint 1 at 0x77cbc6: file prepjointree.c, line 157.
(gdb) c
Continuing.
Breakpoint 1, pull_up_sublinks (root=0x126fd48) at prepjointree.c:157
157 (Node *) root->parse->jointree,
(gdb)
#檢視輸入引數
(gdb) p *root
$1 = {type = T_PlannerInfo, parse = 0x11b43d8, glob = 0x11b4e00, query_level = 1, parent_root = 0x0, plan_params = 0x0,
outer_params = 0x0, simple_rel_array = 0x0, simple_rel_array_size = 0, simple_rte_array = 0x0, 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 = 0x0, 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 = 0x0, grouping_map = 0x0, minmax_aggs = 0x0, planner_cxt = 0x11b2e90, total_table_pages = 0,
tuple_fraction = 0, limit_tuples = 0, qual_security_level = 0, inhTargetKind = INHKIND_NONE, hasJoinRTEs = false,
hasLateralRTEs = false, 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}
#jointree的型別為FromExpr
(gdb) p *root->parse->jointree
$3 = {type = T_FromExpr, fromlist = 0x11b4870, quals = 0x11b40e8}
(gdb) n
156 jtnode = pull_up_sublinks_jointree_recurse(root,
#進入pull_up_sublinks_jointree_recurse函式
(gdb) step
pull_up_sublinks_jointree_recurse (root=0x126fd48, jtnode=0x1282ea0, relids=0x7ffe830ab9b0) at prepjointree.c:180
180 if (jtnode == NULL)
#檢視引數
#1.root與pull_up_sublinks函式的輸入一致
#2.jtnode型別為FromExpr
#3.relids
(gdb) p *jtnode
$7 = {type = T_FromExpr}
(gdb) p *(FromExpr *)jtnode
$8 = {type = T_FromExpr, fromlist = 0x11b4870, quals = 0x11b40e8}
#FromExpr->fromlist中的的元素型別為RangeTblRef
(gdb) p *((FromExpr *)jtnode)->fromlist
$9 = {type = T_List, length = 1, head = 0x11b4850, tail = 0x11b4850}
(gdb) p *(Node *)((FromExpr *)jtnode)->fromlist->head->data.ptr_value
$10 = {type = T_RangeTblRef}
...
#進入FromExpr分支
191 else if (IsA(jtnode, FromExpr))
...
201 foreach(l, f->fromlist)
(gdb)
207 lfirst(l),
(gdb) p *l
$11 = {data = {ptr_value = 0x11b4838, int_value = 18565176, oid_value = 18565176}, next = 0x0}
(gdb) p *(RangeTblRef *)l->data.ptr_value
$13 = {type = T_RangeTblRef, rtindex = 1}
#遞迴呼叫pull_up_sublinks_jointree_recurse
(gdb) n
206 newchild = pull_up_sublinks_jointree_recurse(root,
(gdb) step
pull_up_sublinks_jointree_recurse (root=0x126fd48, jtnode=0x11b4838, relids=0x7ffe830ab940) at prepjointree.c:180
180 if (jtnode == NULL)
#輸入引數
#1.root與pull_up_sublinks函式的輸入一致
#2.jtnode型別為RangeTblRef
#3.relids
#進入RangeTblRef分支
(gdb) n
184 else if (IsA(jtnode, RangeTblRef))
(gdb) n
186 int varno = ((RangeTblRef *) jtnode)->rtindex;
(gdb)
188 *relids = bms_make_singleton(varno);
(gdb)
312 return jtnode;
(gdb) p *relids
$16 = (Relids) 0x12704c8
...
(gdb) p *newchild
$19 = {type = T_RangeTblRef}
(gdb) n
210 frelids = bms_join(frelids, childrelids);
(gdb) p *frelids
$25 = {nwords = 1, words = 0x12704cc}
(gdb) p *frelids->words
$26 = 2
...
#進入pull_up_sublinks_qual_recurse
(gdb) n
217 newf->quals = pull_up_sublinks_qual_recurse(root, f->quals,
(gdb) step
pull_up_sublinks_qual_recurse (root=0x126fd48, node=0x11b40e8, jtlink1=0x7ffe830ab948, available_rels1=0x12704c8,
jtlink2=0x0, available_rels2=0x0) at prepjointree.c:335
335 if (node == NULL)
#輸入引數
#1.root與上述無異
#2.node
(gdb) p *node
$35 = {type = T_SubLink}
(gdb) p *(SubLink *)node
$36 = {xpr = {type = T_SubLink}, subLinkType = ALL_SUBLINK, subLinkId = 0, testexpr = 0x1282e00, operName = 0x11b3cf8,
subselect = 0x1282578, location = 35}
#3.jtlink1,指標陣列
(gdb) p *(RangeTblRef *)((FromExpr *)jtlink1[0])->fromlist->head->data->ptr_value
$45 = {type = T_RangeTblRef, rtindex = 1}
#4.available_rels1,可用的Relids
(gdb) p *available_rels1
$47 = {nwords = 1, words = 0x12704cc}
(gdb) p *available_rels1->words
$48 = 2
#5/6,NULL值
(gdb) n
337 if (IsA(node, SubLink))
(gdb)
339 SubLink *sublink = (SubLink *) node;
(gdb)
344 if (sublink->subLinkType == ANY_SUBLINK)
(gdb)
398 else if (sublink->subLinkType == EXISTS_SUBLINK)
(gdb) p sublink->subLinkType
$49 = ALL_SUBLINK
#非ANY/EXISTS連結,退出
(gdb) n
453 return node;
(gdb)
#回到pull_up_sublinks_jointree_recurse
(gdb)
pull_up_sublinks_jointree_recurse (root=0x126fd48, jtnode=0x1282ea0, relids=0x7ffe830ab9b0) at prepjointree.c:230
230 *relids = frelids;
(gdb)
231 jtnode = jtlink;
(gdb)
312 return jtnode;
#返回的jtnode為RangeTblRef
(gdb) p *(RangeTblRef *)((FromExpr *)jtnode)->fromlist->head->data.ptr_value
$55 = {type = T_RangeTblRef, rtindex = 1}
(gdb) n
313 }
(gdb)
pull_up_sublinks (root=0x126fd48) at prepjointree.c:164
164 if (IsA(jtnode, FromExpr))
(gdb)
165 root->parse->jointree = (FromExpr *) jtnode;
(gdb) p *root->parse->jointree
$56 = {type = T_FromExpr, fromlist = 0x11b4870, quals = 0x11b40e8}
(gdb) p *root->parse->jointree->fromlist
$57 = {type = T_List, length = 1, head = 0x11b4850, tail = 0x11b4850}
(gdb) n
168 }
(gdb)
subquery_planner (glob=0x11b4e00, parse=0x11b43d8, parent_root=0x0, hasRecursion=false, tuple_fraction=0) at planner.c:656
656 inline_set_returning_functions(root);
(gdb) c
Continuing.
#ANY型別並沒有做上拉操作
五、小結
1、基本概念：subLink的基本概念以及基本分類；
2、函式：Planner的主函式簡要介紹；
3、資料結構：SubLink、SubLinkType等結構；
4、上拉操作：只對ANY/EXISTS進行處理，其他型別如ALL暫不處理。
來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/6906/viewspace-2374890/，如需轉載，請註明出處，否則將追究法律責任。
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