PostgreSQL 原始碼解讀（40）- 查詢語句#25（query_planner函式#3）
上一小節介紹了函式query_planner的主處理邏輯以及setup_simple_rel_arrays和setup_append_rel_array兩個子函式的實現邏輯,本節繼續介紹函式query_planner中的add_base_rels_to_query函式。
一、重要的資料結構
Relation
/*
* Here are the contents of a relation cache entry.
*/
typedef struct RelationData
{
RelFileNode rd_node; /* relation physical identifier */
/* use "struct" here to avoid needing to include smgr.h: */
struct SMgrRelationData *rd_smgr; /* cached file handle, or NULL */
int rd_refcnt; /* reference count */
BackendId rd_backend; /* owning backend id, if temporary relation */
bool rd_islocaltemp; /* rel is a temp rel of this session */
bool rd_isnailed; /* rel is nailed in cache */
bool rd_isvalid; /* relcache entry is valid */
char rd_indexvalid; /* state of rd_indexlist: 0 = not valid, 1 =
* valid, 2 = temporarily forced */
bool rd_statvalid; /* is rd_statlist valid? */
/*
* rd_createSubid is the ID of the highest subtransaction the rel has
* survived into; or zero if the rel was not created in the current top
* transaction. This can be now be relied on, whereas previously it could
* be "forgotten" in earlier releases. Likewise, rd_newRelfilenodeSubid is
* the ID of the highest subtransaction the relfilenode change has
* survived into, or zero if not changed in the current transaction (or we
* have forgotten changing it). rd_newRelfilenodeSubid can be forgotten
* when a relation has multiple new relfilenodes within a single
* transaction, with one of them occurring in a subsequently aborted
* subtransaction, e.g. BEGIN; TRUNCATE t; SAVEPOINT save; TRUNCATE t;
* ROLLBACK TO save; -- rd_newRelfilenode is now forgotten
*/
SubTransactionId rd_createSubid; /* rel was created in current xact */
SubTransactionId rd_newRelfilenodeSubid; /* new relfilenode assigned in
* current xact */
Form_pg_class rd_rel; /* RELATION tuple */
TupleDesc rd_att; /* tuple descriptor */
Oid rd_id; /* relation's object id */
LockInfoData rd_lockInfo; /* lock mgr's info for locking relation */
RuleLock *rd_rules; /* rewrite rules */
MemoryContext rd_rulescxt; /* private memory cxt for rd_rules, if any */
TriggerDesc *trigdesc; /* Trigger info, or NULL if rel has none */
/* use "struct" here to avoid needing to include rowsecurity.h: */
struct RowSecurityDesc *rd_rsdesc; /* row security policies, or NULL */
/* data managed by RelationGetFKeyList: */
List *rd_fkeylist; /* list of ForeignKeyCacheInfo (see below) */
bool rd_fkeyvalid; /* true if list has been computed */
MemoryContext rd_partkeycxt; /* private memory cxt for the below */
struct PartitionKeyData *rd_partkey; /* partition key, or NULL */
MemoryContext rd_pdcxt; /* private context for partdesc */
struct PartitionDescData *rd_partdesc; /* partitions, or NULL */
List *rd_partcheck; /* partition CHECK quals */
/* data managed by RelationGetIndexList: */
List *rd_indexlist; /* list of OIDs of indexes on relation */
Oid rd_oidindex; /* OID of unique index on OID, if any */
Oid rd_pkindex; /* OID of primary key, if any */
Oid rd_replidindex; /* OID of replica identity index, if any */
/* data managed by RelationGetStatExtList: */
List *rd_statlist; /* list of OIDs of extended stats */
/* data managed by RelationGetIndexAttrBitmap: */
Bitmapset *rd_indexattr; /* columns used in non-projection indexes */
Bitmapset *rd_projindexattr; /* columns used in projection indexes */
Bitmapset *rd_keyattr; /* cols that can be ref'd by foreign keys */
Bitmapset *rd_pkattr; /* cols included in primary key */
Bitmapset *rd_idattr; /* included in replica identity index */
Bitmapset *rd_projidx; /* Oids of projection indexes */
PublicationActions *rd_pubactions; /* publication actions */
/*
* rd_options is set whenever rd_rel is loaded into the relcache entry.
* Note that you can NOT look into rd_rel for this data. NULL means "use
* defaults".
*/
bytea *rd_options; /* parsed pg_class.reloptions */
/* These are non-NULL only for an index relation: */
Form_pg_index rd_index; /* pg_index tuple describing this index */
/* use "struct" here to avoid needing to include htup.h: */
struct HeapTupleData *rd_indextuple; /* all of pg_index tuple */
/*
* index access support info (used only for an index relation)
*
* Note: only default support procs for each opclass are cached, namely
* those with lefttype and righttype equal to the opclass's opcintype. The
* arrays are indexed by support function number, which is a sufficient
* identifier given that restriction.
*
* Note: rd_amcache is available for index AMs to cache private data about
* an index. This must be just a cache since it may get reset at any time
* (in particular, it will get reset by a relcache inval message for the
* index). If used, it must point to a single memory chunk palloc'd in
* rd_indexcxt. A relcache reset will include freeing that chunk and
* setting rd_amcache = NULL.
*/
Oid rd_amhandler; /* OID of index AM's handler function */
MemoryContext rd_indexcxt; /* private memory cxt for this stuff */
/* use "struct" here to avoid needing to include amapi.h: */
struct IndexAmRoutine *rd_amroutine; /* index AM's API struct */
Oid *rd_opfamily; /* OIDs of op families for each index col */
Oid *rd_opcintype; /* OIDs of opclass declared input data types */
RegProcedure *rd_support; /* OIDs of support procedures */
FmgrInfo *rd_supportinfo; /* lookup info for support procedures */
int16 *rd_indoption; /* per-column AM-specific flags */
List *rd_indexprs; /* index expression trees, if any */
List *rd_indpred; /* index predicate tree, if any */
Oid *rd_exclops; /* OIDs of exclusion operators, if any */
Oid *rd_exclprocs; /* OIDs of exclusion ops' procs, if any */
uint16 *rd_exclstrats; /* exclusion ops' strategy numbers, if any */
void *rd_amcache; /* available for use by index AM */
Oid *rd_indcollation; /* OIDs of index collations */
/*
* foreign-table support
*
* rd_fdwroutine must point to a single memory chunk palloc'd in
* CacheMemoryContext. It will be freed and reset to NULL on a relcache
* reset.
*/
/* use "struct" here to avoid needing to include fdwapi.h: */
struct FdwRoutine *rd_fdwroutine; /* cached function pointers, or NULL */
/*
* Hack for CLUSTER, rewriting ALTER TABLE, etc: when writing a new
* version of a table, we need to make any toast pointers inserted into it
* have the existing toast table's OID, not the OID of the transient toast
* table. If rd_toastoid isn't InvalidOid, it is the OID to place in
* toast pointers inserted into this rel. (Note it's set on the new
* version of the main heap, not the toast table itself.) This also
* causes toast_save_datum() to try to preserve toast value OIDs.
*/
Oid rd_toastoid; /* Real TOAST table's OID, or InvalidOid */
/* use "struct" here to avoid needing to include pgstat.h: */
struct PgStat_TableStatus *pgstat_info; /* statistics collection area */
} RelationData;
typedef struct RelationData *Relation;
IndexOptInfo
索引資訊
/*
* IndexOptInfo
* Per-index information for planning/optimization
*
* indexkeys[], indexcollations[] each have ncolumns entries.
* opfamily[], and opcintype[] each have nkeycolumns entries. They do
* not contain any information about included attributes.
*
* sortopfamily[], reverse_sort[], and nulls_first[] have
* nkeycolumns entries, if the index is ordered; but if it is unordered,
* those pointers are NULL.
*
* Zeroes in the indexkeys[] array indicate index columns that are
* expressions; there is one element in indexprs for each such column.
*
* For an ordered index, reverse_sort[] and nulls_first[] describe the
* sort ordering of a forward indexscan; we can also consider a backward
* indexscan, which will generate the reverse ordering.
*
* The indexprs and indpred expressions have been run through
* prepqual.c and eval_const_expressions() for ease of matching to
* WHERE clauses. indpred is in implicit-AND form.
*
* indextlist is a TargetEntry list representing the index columns.
* It provides an equivalent base-relation Var for each simple column,
* and links to the matching indexprs element for each expression column.
*
* While most of these fields are filled when the IndexOptInfo is created
* (by plancat.c), indrestrictinfo and predOK are set later, in
* check_index_predicates().
*/
typedef struct IndexOptInfo
{
NodeTag type;
Oid indexoid; /* Index的OID,OID of the index relation */
Oid reltablespace; /* Index的表空間,tablespace of index (not table) */
RelOptInfo *rel; /* 指向Relation的指標,back-link to index's table */
/* index-size statistics (from pg_class and elsewhere) */
BlockNumber pages; /* Index的pages,number of disk pages in index */
double tuples; /* Index的元組數,number of index tuples in index */
int tree_height; /* 索引高度,index tree height, or -1 if unknown */
/* index descriptor information */
int ncolumns; /* 索引的列數,number of columns in index */
int nkeycolumns; /* 索引的關鍵列數,number of key columns in index */
int *indexkeys; /* column numbers of index's attributes both
* key and included columns, or 0 */
Oid *indexcollations; /* OIDs of collations of index columns */
Oid *opfamily; /* OIDs of operator families for columns */
Oid *opcintype; /* OIDs of opclass declared input data types */
Oid *sortopfamily; /* OIDs of btree opfamilies, if orderable */
bool *reverse_sort; /* 倒序?is sort order descending? */
bool *nulls_first; /* NULLs值優先?do NULLs come first in the sort order? */
bool *canreturn; /* 索引列可透過Index-Only Scan返回?which index cols can be returned in an
* index-only scan? */
Oid relam; /* 訪問方法OID,OID of the access method (in pg_am) */
List *indexprs; /* 非簡單索引列表示式連結串列,如函式索引,expressions for non-simple index columns */
List *indpred; /* predicate if a partial index, else NIL */
List *indextlist; /* 投影列?targetlist representing index columns */
List *indrestrictinfo; /* 索引約束條件,parent relation's baserestrictinfo
* list, less any conditions implied by
* the index's predicate (unless it's a
* target rel, see comments in
* check_index_predicates()) */
bool predOK; /* True,如索引前導滿足查詢要求,true if index predicate matches query */
bool unique; /* 唯一索引?true if a unique index */
bool immediate; /* 唯一性校驗是否立即生效?is uniqueness enforced immediately? */
bool hypothetical; /* 虛擬索引?true if index doesn't really exist */
/* Remaining fields are copied from the index AM's API struct: */
//從Index Relation複製過來的AM(訪問方法)API資訊
bool amcanorderbyop; /* does AM support order by operator result? */
bool amoptionalkey; /* can query omit key for the first column? */
bool amsearcharray; /* can AM handle ScalarArrayOpExpr quals? */
bool amsearchnulls; /* can AM search for NULL/NOT NULL entries? */
bool amhasgettuple; /* does AM have amgettuple interface? */
bool amhasgetbitmap; /* does AM have amgetbitmap interface? */
bool amcanparallel; /* does AM support parallel scan? */
/* Rather than include amapi.h here, we declare amcostestimate like this */
void (*amcostestimate) (); /* 訪問方法的估算函式,AM's cost estimator */
} IndexOptInfo;
ForeignKeyOptInfo
外來鍵最佳化資訊
/*
* ForeignKeyOptInfo
* Per-foreign-key information for planning/optimization
*
* The per-FK-column arrays can be fixed-size because we allow at most
* INDEX_MAX_KEYS columns in a foreign key constraint. Each array has
* nkeys valid entries.
*/
typedef struct ForeignKeyOptInfo
{
NodeTag type;
/* Basic data about the foreign key (fetched from catalogs): */
Index con_relid; /* RT index of the referencing table */
Index ref_relid; /* RT index of the referenced table */
int nkeys; /* number of columns in the foreign key */
AttrNumber conkey[INDEX_MAX_KEYS]; /* cols in referencing table */
AttrNumber confkey[INDEX_MAX_KEYS]; /* cols in referenced table */
Oid conpfeqop[INDEX_MAX_KEYS]; /* PK = FK operator OIDs */
/* Derived info about whether FK's equality conditions match the query: */
int nmatched_ec; /* # of FK cols matched by ECs */
int nmatched_rcols; /* # of FK cols matched by non-EC rinfos */
int nmatched_ri; /* total # of non-EC rinfos matched to FK */
/* Pointer to eclass matching each column's condition, if there is one */
struct EquivalenceClass *eclass[INDEX_MAX_KEYS];
/* List of non-EC RestrictInfos matching each column's condition */
List *rinfos[INDEX_MAX_KEYS];
} ForeignKeyOptInfo;
StatisticExtInfo
/*
* StatisticExtInfo
* Information about extended statistics for planning/optimization
*
* Each pg_statistic_ext row is represented by one or more nodes of this
* type, or even zero if ANALYZE has not computed them.
*/
typedef struct StatisticExtInfo
{
NodeTag type;
Oid statOid; /* OID of the statistics row */
RelOptInfo *rel; /* back-link to statistic's table */
char kind; /* statistic kind of this entry */
Bitmapset *keys; /* attnums of the columns covered */
} StatisticExtInfo;
二、原始碼解讀
add_base_rels_to_query函式構建查詢的RelOptInfos
add_base_rels_to_query
/*
* add_base_rels_to_query
*
* Scan the query's jointree and create baserel RelOptInfos for all
* the base relations (ie, table, subquery, and function RTEs)
* appearing in the jointree.
*
* The initial invocation must pass root->parse->jointree as the value of
* jtnode. Internally, the function recurses through the jointree.
*
* At the end of this process, there should be one baserel RelOptInfo for
* every non-join RTE that is used in the query. Therefore, this routine
* is the only place that should call build_simple_rel with reloptkind
* RELOPT_BASEREL. (Note: build_simple_rel recurses internally to build
* "other rel" RelOptInfos for the members of any appendrels we find here.)
*/
void
add_base_rels_to_query(PlannerInfo *root, Node *jtnode)//遍歷jointree遞迴實現
{
//以下的遞迴遍歷結構先前的內容已反覆出現N次
if (jtnode == NULL)
return;
if (IsA(jtnode, RangeTblRef))//RTR
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
(void) build_simple_rel(root, varno, NULL);
}
else if (IsA(jtnode, FromExpr))//FromExpr
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
foreach(l, f->fromlist)//fromlist
add_base_rels_to_query(root, lfirst(l));
}
else if (IsA(jtnode, JoinExpr))//JoinExpr
{
JoinExpr *j = (JoinExpr *) jtnode;
add_base_rels_to_query(root, j->larg);//左Child
add_base_rels_to_query(root, j->rarg);//右Child
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
}
/*
* build_simple_rel
* Construct a new RelOptInfo for a base relation or 'other' relation.
*/
RelOptInfo *
build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
{
RelOptInfo *rel;
RangeTblEntry *rte;
/* Rel should not exist already */
Assert(relid > 0 && relid < root->simple_rel_array_size);
if (root->simple_rel_array[relid] != NULL)
elog(ERROR, "rel %d already exists", relid);
/* Fetch RTE for relation */
rte = root->simple_rte_array[relid];//獲取RTE
Assert(rte != NULL);
rel = makeNode(RelOptInfo);//構建RelOptInfo
rel->reloptkind = parent ? RELOPT_OTHER_MEMBER_REL : RELOPT_BASEREL;
rel->relids = bms_make_singleton(relid);//初始化relids
rel->rows = 0;
/* cheap startup cost is interesting iff not all tuples to be retrieved */
rel->consider_startup = (root->tuple_fraction > 0);
rel->consider_param_startup = false; /* might get changed later */
rel->consider_parallel = false; /* might get changed later */
rel->reltarget = create_empty_pathtarget();
rel->pathlist = NIL;
rel->ppilist = NIL;
rel->partial_pathlist = NIL;
rel->cheapest_startup_path = NULL;
rel->cheapest_total_path = NULL;
rel->cheapest_unique_path = NULL;
rel->cheapest_parameterized_paths = NIL;
rel->direct_lateral_relids = NULL;
rel->lateral_relids = NULL;
rel->relid = relid;
rel->rtekind = rte->rtekind;
/* min_attr, max_attr, attr_needed, attr_widths are set below */
rel->lateral_vars = NIL;
rel->lateral_referencers = NULL;
rel->indexlist = NIL;
rel->statlist = NIL;
rel->pages = 0;
rel->tuples = 0;
rel->allvisfrac = 0;
rel->subroot = NULL;
rel->subplan_params = NIL;
rel->rel_parallel_workers = -1; /* set up in get_relation_info */
rel->serverid = InvalidOid;
rel->userid = rte->checkAsUser;
rel->useridiscurrent = false;
rel->fdwroutine = NULL;
rel->fdw_private = NULL;
rel->unique_for_rels = NIL;
rel->non_unique_for_rels = NIL;
rel->baserestrictinfo = NIL;
rel->baserestrictcost.startup = 0;
rel->baserestrictcost.per_tuple = 0;
rel->baserestrict_min_security = UINT_MAX;
rel->joininfo = NIL;
rel->has_eclass_joins = false;
rel->consider_partitionwise_join = false; /* might get changed later */
rel->part_scheme = NULL;
rel->nparts = 0;
rel->boundinfo = NULL;
rel->partition_qual = NIL;
rel->part_rels = NULL;
rel->partexprs = NULL;
rel->nullable_partexprs = NULL;
rel->partitioned_child_rels = NIL;
/*
* Pass top parent's relids down the inheritance hierarchy. If the parent
* has top_parent_relids set, it's a direct or an indirect child of the
* top parent indicated by top_parent_relids. By extension this child is
* also an indirect child of that parent.
*/
if (parent)//存在父RelOptInfo,設定top_parent_relids變數(最上層的Relids)
{
if (parent->top_parent_relids)
rel->top_parent_relids = parent->top_parent_relids;
else
rel->top_parent_relids = bms_copy(parent->relids);
}
else
rel->top_parent_relids = NULL;
/* Check type of rtable entry */
switch (rte->rtekind)
{
case RTE_RELATION:
/* Table --- retrieve statistics from the system catalogs */
get_relation_info(root, rte->relid, rte->inh, rel);//基表,從資料字典中獲取統計資訊
break;
case RTE_SUBQUERY:
case RTE_FUNCTION:
case RTE_TABLEFUNC:
case RTE_VALUES:
case RTE_CTE:
case RTE_NAMEDTUPLESTORE:
/*
* 子查詢/函式/tablefunc/values lis/CTE/ENR,設定屬性範圍&陣列
* Subquery, function, tablefunc, values list, CTE, or ENR --- set
* up attr range and arrays
*
* Note: 0 is included in range to support whole-row Vars
*/
rel->min_attr = 0;
rel->max_attr = list_length(rte->eref->colnames);
rel->attr_needed = (Relids *)
palloc0((rel->max_attr - rel->min_attr + 1) * sizeof(Relids));
rel->attr_widths = (int32 *)
palloc0((rel->max_attr - rel->min_attr + 1) * sizeof(int32));
break;
default:
elog(ERROR, "unrecognized RTE kind: %d",
(int) rte->rtekind);
break;
}
/* Save the finished struct in the query's simple_rel_array */
root->simple_rel_array[relid] = rel;//儲存RelOptInfo
/*
* This is a convenient spot at which to note whether rels participating
* in the query have any securityQuals attached. If so, increase
* root->qual_security_level to ensure it's larger than the maximum
* security level needed for securityQuals.
*/
if (rte->securityQuals)
root->qual_security_level = Max(root->qual_security_level,
list_length(rte->securityQuals));
/*
* If this rel is an appendrel parent, recurse to build "other rel"
* RelOptInfos for its children. They are "other rels" because they are
* not in the main join tree, but we will need RelOptInfos to plan access
* to them.
*/
//如果這個RelOptInfo是一個appendrel的父節點,遞迴的構建其children對應的RelOptInfos
if (rte->inh)
{
ListCell *l;
int nparts = rel->nparts;
int cnt_parts = 0;
if (nparts > 0)
rel->part_rels = (RelOptInfo **)
palloc(sizeof(RelOptInfo *) * nparts);
foreach(l, root->append_rel_list)//遞迴呼叫
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
RelOptInfo *childrel;
/* append_rel_list contains all append rels; ignore others */
if (appinfo->parent_relid != relid)
continue;
childrel = build_simple_rel(root, appinfo->child_relid,
rel);
/* Nothing more to do for an unpartitioned table. */
if (!rel->part_scheme)
continue;
/*
* The order of partition OIDs in append_rel_list is the same as
* the order in the PartitionDesc, so the order of part_rels will
* also match the PartitionDesc. See expand_partitioned_rtentry.
*/
Assert(cnt_parts < nparts);
rel->part_rels[cnt_parts] = childrel;
cnt_parts++;
}
/* We should have seen all the child partitions. */
Assert(cnt_parts == nparts);
}
return rel;
}
/*
* get_relation_info -
* Retrieves catalog information for a given relation.
*
* Given the Oid of the relation, return the following info into fields
* of the RelOptInfo struct:
*
* min_attr lowest valid AttrNumber 最小有效屬性編號
* max_attr highest valid AttrNumber 最大有效屬性編號
* indexlist list of IndexOptInfos for relation's indexes 索引的IndexOptInfo連結串列
* statlist list of StatisticExtInfo for relation's statistic objects 擴充套件統計資訊連結串列
* serverid if it's a foreign table, the server OID FDW所在伺服器ID
* fdwroutine if it's a foreign table, the FDW function pointers FDW函式指標
* pages number of pages pages數
* tuples number of tuples 元組數
* rel_parallel_workers user-defined number of parallel workers 使用者自定義的並行worker數
*
* Also, add information about the relation's foreign keys to root->fkey_list.
*
* Relation的外來鍵資訊會新增到root->fkey_list中
*
* Also, initialize the attr_needed[] and attr_widths[] arrays. In most
* cases these are left as zeroes, but sometimes we need to compute attr
* widths here, and we may as well cache the results for costsize.c.
*
* If inhparent is true, all we need to do is set up the attr arrays:
* the RelOptInfo actually represents the appendrel formed by an inheritance
* tree, and so the parent rel's physical size and index information isn't
* important for it.
*/
void
get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
RelOptInfo *rel)
{
Index varno = rel->relid;//Relation的relid
Relation relation;//Relation資訊
bool hasindex;//是否含有index
List *indexinfos = NIL;//IndexOptInfo連結串列
/*
* We need not lock the relation since it was already locked, either by
* the rewriter or when expand_inherited_rtentry() added it to the query's
* rangetable.
*/
relation = heap_open(relationObjectId, NoLock);//Relation資訊
/* Temporary and unlogged relations are inaccessible during recovery. */
if (!RelationNeedsWAL(relation) && RecoveryInProgress())//恢復過程不允許訪問
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot access temporary or unlogged relations during recovery")));
rel->min_attr = FirstLowInvalidHeapAttributeNumber + 1;//(FirstLowInvalidHeapAttributeNumber=-8)
//#define RelationGetNumberOfAttributes(relation) ((relation)->rd_rel->relnatts)
rel->max_attr = RelationGetNumberOfAttributes(relation);//
rel->reltablespace = RelationGetForm(relation)->reltablespace;//表空間
Assert(rel->max_attr >= rel->min_attr);
rel->attr_needed = (Relids *)
palloc0((rel->max_attr - rel->min_attr + 1) * sizeof(Relids));//初始化
rel->attr_widths = (int32 *)
palloc0((rel->max_attr - rel->min_attr + 1) * sizeof(int32));//初始化
/*
* Estimate relation size --- unless it's an inheritance parent, in which
* case the size will be computed later in set_append_rel_pathlist, and we
* must leave it zero for now to avoid bollixing the total_table_pages
* calculation.
*/
//如果不是inheritance parent,則估算Relation的大小
if (!inhparent)
estimate_rel_size(relation, rel->attr_widths - rel->min_attr,
&rel->pages, &rel->tuples, &rel->allvisfrac);
/* Retrieve the parallel_workers reloption, or -1 if not set. */
/*
#define RelationGetParallelWorkers(relation, defaultpw) \
((relation)->rd_options ? \
((StdRdOptions *) (relation)->rd_options)->parallel_workers : (defaultpw))
*/
rel->rel_parallel_workers = RelationGetParallelWorkers(relation, -1);
/*
* Make list of indexes. Ignore indexes on system catalogs if told to.
* Don't bother with indexes for an inheritance parent, either.
*/
if (inhparent ||
(IgnoreSystemIndexes && IsSystemRelation(relation)))//繼承表/系統表並且忽略索引
hasindex = false;
else
hasindex = relation->rd_rel->relhasindex;//是否含有索引
if (hasindex)//存在索引,則生成IndexOptInfo連結串列
{
List *indexoidlist;
ListCell *l;
LOCKMODE lmode;
indexoidlist = RelationGetIndexList(relation);//獲取Relation的Index Oid連結串列
/*
* For each index, we get the same type of lock that the executor will
* need, and do not release it. This saves a couple of trips to the
* shared lock manager while not creating any real loss of
* concurrency, because no schema changes could be happening on the
* index while we hold lock on the parent rel, and neither lock type
* blocks any other kind of index operation.
*/
if (rel->relid == root->parse->resultRelation)
lmode = RowExclusiveLock;//該Relation是結果Relation,鎖模式為行排它鎖
else
lmode = AccessShareLock;//否則為訪問共享鎖
foreach(l, indexoidlist)//遍歷Index Oid
{
Oid indexoid = lfirst_oid(l);
Relation indexRelation;
Form_pg_index index;
IndexAmRoutine *amroutine;
IndexOptInfo *info;
int ncolumns,
nkeycolumns;
int i;
/*
* Extract info from the relation descriptor for the index.
*/
indexRelation = index_open(indexoid, lmode);//獲取Index相關資訊
index = indexRelation->rd_index;
/*
* Ignore invalid indexes, since they can't safely be used for
* queries. Note that this is OK because the data structure we
* are constructing is only used by the planner --- the executor
* still needs to insert into "invalid" indexes, if they're marked
* IndexIsReady.
*/
if (!IndexIsValid(index))
{
index_close(indexRelation, NoLock);//忽略無效的Index
continue;
}
/*
* Ignore partitioned indexes, since they are not usable for
* queries.
*/
if (indexRelation->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
{
index_close(indexRelation, NoLock);//忽略分割槽索引
continue;
}
/*
* If the index is valid, but cannot yet be used, ignore it; but
* mark the plan we are generating as transient. See
* src/backend/access/heap/README.HOT for discussion.
*/
if (index->indcheckxmin &&
!TransactionIdPrecedes(HeapTupleHeaderGetXmin(indexRelation->rd_indextuple->t_data),
TransactionXmin))
{
root->glob->transientPlan = true;//有效索引,但還不能正常使用,忽略之
index_close(indexRelation, NoLock);
continue;
}
info = makeNode(IndexOptInfo);//建立IndexOptInfo節點
info->indexoid = index->indexrelid;//OID
info->reltablespace =
RelationGetForm(indexRelation)->reltablespace;//表空間
info->rel = rel;//Index所在的Relation
info->ncolumns = ncolumns = index->indnatts;//Index的列個數
info->nkeycolumns = nkeycolumns = index->indnkeyatts;//
info->indexkeys = (int *) palloc(sizeof(int) * ncolumns);//初始化記憶體空間
info->indexcollations = (Oid *) palloc(sizeof(Oid) * nkeycolumns);
info->opfamily = (Oid *) palloc(sizeof(Oid) * nkeycolumns);
info->opcintype = (Oid *) palloc(sizeof(Oid) * nkeycolumns);
info->canreturn = (bool *) palloc(sizeof(bool) * ncolumns);
for (i = 0; i < ncolumns; i++)//索引鍵
{
info->indexkeys[i] = index->indkey.values[i];
info->canreturn[i] = index_can_return(indexRelation, i + 1);
}
for (i = 0; i < nkeycolumns; i++)//索引鍵屬性
{
info->opfamily[i] = indexRelation->rd_opfamily[i];
info->opcintype[i] = indexRelation->rd_opcintype[i];
info->indexcollations[i] = indexRelation->rd_indcollation[i];
}
info->relam = indexRelation->rd_rel->relam;//?
/* We copy just the fields we need, not all of rd_amroutine */
amroutine = indexRelation->rd_amroutine;//複製IndexRelation中的資訊
info->amcanorderbyop = amroutine->amcanorderbyop;
info->amoptionalkey = amroutine->amoptionalkey;
info->amsearcharray = amroutine->amsearcharray;
info->amsearchnulls = amroutine->amsearchnulls;
info->amcanparallel = amroutine->amcanparallel;
info->amhasgettuple = (amroutine->amgettuple != NULL);
info->amhasgetbitmap = (amroutine->amgetbitmap != NULL);
info->amcostestimate = amroutine->amcostestimate;
Assert(info->amcostestimate != NULL);
/*
* Fetch the ordering information for the index, if any.
*/
if (info->relam == BTREE_AM_OID)//BTree
{
/*
* If it's a btree index, we can use its opfamily OIDs
* directly as the sort ordering opfamily OIDs.
*/
Assert(amroutine->amcanorder);
info->sortopfamily = info->opfamily;
info->reverse_sort = (bool *) palloc(sizeof(bool) * nkeycolumns);
info->nulls_first = (bool *) palloc(sizeof(bool) * nkeycolumns);
for (i = 0; i < nkeycolumns; i++)
{
int16 opt = indexRelation->rd_indoption[i];
info->reverse_sort[i] = (opt & INDOPTION_DESC) != 0;
info->nulls_first[i] = (opt & INDOPTION_NULLS_FIRST) != 0;
}
}
else if (amroutine->amcanorder)//可排序的訪問方法
{
/*
* Otherwise, identify the corresponding btree opfamilies by
* trying to map this index's "<" operators into btree. Since
* "<" uniquely defines the behavior of a sort order, this is
* a sufficient test.
*
* XXX This method is rather slow and also requires the
* undesirable assumption that the other index AM numbers its
* strategies the same as btree. It'd be better to have a way
* to explicitly declare the corresponding btree opfamily for
* each opfamily of the other index type. But given the lack
* of current or foreseeable amcanorder index types, it's not
* worth expending more effort on now.
*/
info->sortopfamily = (Oid *) palloc(sizeof(Oid) * nkeycolumns);
info->reverse_sort = (bool *) palloc(sizeof(bool) * nkeycolumns);
info->nulls_first = (bool *) palloc(sizeof(bool) * nkeycolumns);
for (i = 0; i < nkeycolumns; i++)
{
int16 opt = indexRelation->rd_indoption[i];
Oid ltopr;
Oid btopfamily;
Oid btopcintype;
int16 btstrategy;
info->reverse_sort[i] = (opt & INDOPTION_DESC) != 0;//是否倒序?
info->nulls_first[i] = (opt & INDOPTION_NULLS_FIRST) != 0;//NULL值優先?
ltopr = get_opfamily_member(info->opfamily[i],
info->opcintype[i],
info->opcintype[i],
BTLessStrategyNumber);
if (OidIsValid(ltopr) &&
get_ordering_op_properties(ltopr,
&btopfamily,
&btopcintype,
&btstrategy) &&
btopcintype == info->opcintype[i] &&
btstrategy == BTLessStrategyNumber)
{
/* Successful mapping */
info->sortopfamily[i] = btopfamily;//排序操作類?
}
else//失敗,索引視為未排序
{
/* Fail ... quietly treat index as unordered */
info->sortopfamily = NULL;
info->reverse_sort = NULL;
info->nulls_first = NULL;
break;
}
}
}
else//非可排序,設定為NULL
{
info->sortopfamily = NULL;
info->reverse_sort = NULL;
info->nulls_first = NULL;
}
/*
* Fetch the index expressions and predicate, if any. We must
* modify the copies we obtain from the relcache to have the
* correct varno for the parent relation, so that they match up
* correctly against qual clauses.
*/
info->indexprs = RelationGetIndexExpressions(indexRelation);//索引表示式(函式索引)
info->indpred = RelationGetIndexPredicate(indexRelation);//索引謂詞資訊(條件索引)
if (info->indexprs && varno != 1)
ChangeVarNodes((Node *) info->indexprs, 1, varno, 0);
if (info->indpred && varno != 1)
ChangeVarNodes((Node *) info->indpred, 1, varno, 0);
/* Build targetlist using the completed indexprs data */
info->indextlist = build_index_tlist(root, info, relation);//索引的列
info->indrestrictinfo = NIL; /* set later, in indxpath.c */
info->predOK = false; /* set later, in indxpath.c */
info->unique = index->indisunique;
info->immediate = index->indimmediate;
info->hypothetical = false;
/*
* Estimate the index size. If it's not a partial index, we lock
* the number-of-tuples estimate to equal the parent table; if it
* is partial then we have to use the same methods as we would for
* a table, except we can be sure that the index is not larger
* than the table.
*/
if (info->indpred == NIL)//非條件索引
{
info->pages = RelationGetNumberOfBlocks(indexRelation);//Index的pages
info->tuples = rel->tuples;//Index的元組
}
else
{
double allvisfrac; /* dummy */
estimate_rel_size(indexRelation, NULL,
&info->pages, &info->tuples, &allvisfrac);//估算Index的大小
if (info->tuples > rel->tuples)//Index的元組數不能大於資料表元組數
info->tuples = rel->tuples;
}
if (info->relam == BTREE_AM_OID)//BTree
{
/* For btrees, get tree height while we have the index open */
info->tree_height = _bt_getrootheight(indexRelation);//BTree高度
}
else
{
/* For other index types, just set it to "unknown" for now */
info->tree_height = -1;//非BTree
}
index_close(indexRelation, NoLock);
indexinfos = lcons(info, indexinfos);
}
list_free(indexoidlist);
}
rel->indexlist = indexinfos;
rel->statlist = get_relation_statistics(rel, relation);
/* Grab foreign-table info using the relcache, while we have it */
if (relation->rd_rel->relkind == RELKIND_FOREIGN_TABLE)//FDW
{
rel->serverid = GetForeignServerIdByRelId(RelationGetRelid(relation));
rel->fdwroutine = GetFdwRoutineForRelation(relation, true);
}
else
{
rel->serverid = InvalidOid;
rel->fdwroutine = NULL;
}
/* Collect info about relation's foreign keys, if relevant */
get_relation_foreign_keys(root, rel, relation, inhparent);//收集外來鍵資訊
/*
* Collect info about relation's partitioning scheme, if any. Only
* inheritance parents may be partitioned.
*/
if (inhparent && relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
set_relation_partition_info(root, rel, relation);//收集分割槽表資訊
heap_close(relation, NoLock);
/*
* Allow a plugin to editorialize on the info we obtained from the
* catalogs. Actions might include altering the assumed relation size,
* removing an index, or adding a hypothetical index to the indexlist.
*/
if (get_relation_info_hook)
(*get_relation_info_hook) (root, relationObjectId, inhparent, rel);//鉤子函式
}
三、跟蹤分析
測試指令碼,建立部分(條件)索引和函式索引:
testdb=# create index idx_dwxx_expr on t_dwxx(trim(dwmc));
CREATE INDEX
testdb=# create index idx_dwxx_predicate on t_dwxx(dwdz) where dwdz like '廣東省%';
CREATE INDEX
testdb=# explain verbose select * from t_dwxx where dwdz like '廣東省%';
QUERY PLAN
---------------------------------------------------------------
Seq Scan on public.t_dwxx (cost=0.00..1.04 rows=1 width=474)
Output: dwmc, dwbh, dwdz
Filter: ((t_dwxx.dwdz)::text ~~ '廣東省%'::text)
(3 rows)
跟蹤分析:
(gdb) b add_base_rels_to_query
Breakpoint 1 at 0x765400: file initsplan.c, line 107.
(gdb) c
Continuing.
Breakpoint 1, add_base_rels_to_query (root=0x23107f8, jtnode=0x2251cc8) at initsplan.c:107
107 if (jtnode == NULL)
(gdb) n
109 if (IsA(jtnode, RangeTblRef))
(gdb)
115 else if (IsA(jtnode, FromExpr))
(gdb)
第一次呼叫,jtnode型別為FromExpr
117 FromExpr *f = (FromExpr *) jtnode;
(gdb)
120 foreach(l, f->fromlist)
(gdb)
121 add_base_rels_to_query(root, lfirst(l));
(gdb)
Breakpoint 1, add_base_rels_to_query (root=0x23107f8, jtnode=0x22515f0) at initsplan.c:107
107 if (jtnode == NULL)
(gdb)
第二次呼叫,型別為RTR
109 if (IsA(jtnode, RangeTblRef))
(gdb)
111 int varno = ((RangeTblRef *) jtnode)->rtindex;
(gdb)
113 (void) build_simple_rel(root, varno, NULL);
(gdb) p varno
$1 = 1
進入build_simple_rel
...
180 switch (rte->rtekind)
(gdb)
184 get_relation_info(root, rte->relid, rte->inh, rel);
進入get_relation_info
檢視Relation的相關資訊:
...
##Relation的相關資訊
121 relation = heap_open(relationObjectId, NoLock);
(gdb)
124 if (!RelationNeedsWAL(relation) && RecoveryInProgress())
(gdb) p *relation
$4 = {rd_node = {spcNode = 1663, dbNode = 16384, relNode = 16394}, rd_smgr = 0x230d358, rd_refcnt = 1, rd_backend = -1,
rd_islocaltemp = false, rd_isnailed = false, rd_isvalid = true, rd_indexvalid = 1 '\001', rd_statvalid = true,
rd_createSubid = 0, rd_newRelfilenodeSubid = 0, rd_rel = 0x7f6b9a010380, rd_att = 0x7f6b99fff5e8, rd_id = 16394,
rd_lockInfo = {lockRelId = {relId = 16394, dbId = 16384}}, rd_rules = 0x0, rd_rulescxt = 0x0, trigdesc = 0x0,
rd_rsdesc = 0x0, rd_fkeylist = 0x0, rd_fkeyvalid = false, rd_partkeycxt = 0x0, rd_partkey = 0x0, rd_pdcxt = 0x0,
rd_partdesc = 0x0, rd_partcheck = 0x0, rd_indexlist = 0x7f6b9a011b80, rd_oidindex = 0, rd_pkindex = 16476,
rd_replidindex = 16476, rd_statlist = 0x0, rd_indexattr = 0x0, rd_projindexattr = 0x0, rd_keyattr = 0x0, rd_pkattr = 0x0,
rd_idattr = 0x0, rd_projidx = 0x0, rd_pubactions = 0x0, rd_options = 0x0, rd_index = 0x0, rd_indextuple = 0x0,
rd_amhandler = 0, rd_indexcxt = 0x0, rd_amroutine = 0x0, rd_opfamily = 0x0, rd_opcintype = 0x0, rd_support = 0x0,
rd_supportinfo = 0x0, rd_indoption = 0x0, rd_indexprs = 0x0, rd_indpred = 0x0, rd_exclops = 0x0, rd_exclprocs = 0x0,
rd_exclstrats = 0x0, rd_amcache = 0x0, rd_indcollation = 0x0, rd_fdwroutine = 0x0, rd_toastoid = 0,
pgstat_info = 0x22d11b8}
##rd_pkindex = 16476,關鍵字對應的OID
##pg_class輸出的結構體
(gdb) p *relation->rd_rel
$5 = {relname = {data = "t_dwxx", '\000' <repeats 57 times>}, relnamespace = 2200, reltype = 16396, reloftype = 0,
relowner = 10, relam = 0, relfilenode = 16394, reltablespace = 0, relpages = 1, reltuples = 3, relallvisible = 0,
reltoastrelid = 0, relhasindex = true, relisshared = false, relpersistence = 112 'p', relkind = 114 'r', relnatts = 3,
relchecks = 0, relhasoids = false, relhasrules = false, relhastriggers = false, relhassubclass = false,
relrowsecurity = false, relforcerowsecurity = false, relispopulated = true, relreplident = 100 'd',
relispartition = false, relrewrite = 0, relfrozenxid = 587, relminmxid = 1}
##屬性(3個)
(gdb) p *relation->rd_att
$6 = {natts = 3, tdtypeid = 16396, tdtypmod = -1, tdhasoid = false, tdrefcount = 1, constr = 0x7f6b99fffb18,
attrs = 0x7f6b99fff608}
(gdb) p relation->rd_att->attrs[0]
$8 = {attrelid = 16394, attname = {data = "dwmc", '\000' <repeats 59 times>}, atttypid = 1043, attstattarget = -1,
attlen = -1, attnum = 1, attndims = 0, attcacheoff = 0, atttypmod = 104, 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 relation->rd_att->attrs[1]
$9 = {attrelid = 16394, attname = {data = "dwbh", '\000' <repeats 59 times>}, atttypid = 1043, attstattarget = -1,
attlen = -1, attnum = 2, attndims = 0, attcacheoff = -1, atttypmod = 14, attbyval = false, attstorage = 120 'x',
attalign = 105 'i', attnotnull = true, atthasdef = false, atthasmissing = false, attidentity = 0 '\000',
attisdropped = false, attislocal = true, attinhcount = 0, attcollation = 100}
(gdb) p relation->rd_att->attrs[3]
$10 = {attrelid = 0, attname = {data = '\000' <repeats 44 times>, "\230\023-\002", '\000' <repeats 15 times>},
atttypid = 0, attstattarget = 0, attlen = 0, attnum = 0, attndims = 0, attcacheoff = 0, atttypmod = 0, attbyval = false,
attstorage = 0 '\000', attalign = 0 '\000', attnotnull = false, atthasdef = false, atthasmissing = false,
attidentity = 0 '\000', attisdropped = false, attislocal = false, attinhcount = 0, attcollation = 0}
##Index相應的OID
(gdb) p relation->rd_indexlist->head->data.oid_value
$12 = 16476
(gdb) p relation->rd_indexlist->head->next->data.oid_value
$13 = 16497
(gdb) p relation->rd_indexlist->head->next->next->data.oid_value
$14 = 16499
...
進入estimate_rel_size
146 estimate_rel_size(relation, rel->attr_widths - rel->min_attr,
(gdb) step
estimate_rel_size (rel=0x7f6b9a00f390, attr_widths=0x231c674, pages=0x23124d8, tuples=0x23124e0, allvisfrac=0x23124e8)
at plancat.c:948
948 switch (rel->rd_rel->relkind)
(gdb) p reltuples
$19 = 3
...
回到get_relation_info
(gdb)
get_relation_info (root=0x23107f8, relationObjectId=16394, inhparent=false, rel=0x2312428) at plancat.c:150
150 rel->rel_parallel_workers = RelationGetParallelWorkers(relation, -1);
獲取索引資訊(IndexOptInfo的獲取在這裡是重點)
162 if (hasindex)
(gdb)
168 indexoidlist = RelationGetIndexList(relation);
...
#第一個Index
(gdb) p indexoid
$2 = 16476
#IndexRelation的相關資訊
(gdb) p *indexRelation
$3 = {rd_node = {spcNode = 1663, dbNode = 16384, relNode = 16476}, rd_smgr = 0x230d3c8, rd_refcnt = 1, rd_backend = -1,
rd_islocaltemp = false, rd_isnailed = false, rd_isvalid = true, rd_indexvalid = 0 '\000', rd_statvalid = false,
rd_createSubid = 0, rd_newRelfilenodeSubid = 0, rd_rel = 0x7f6b99fff7f8, rd_att = 0x7f6b9a00f5a0, rd_id = 16476,
rd_lockInfo = {lockRelId = {relId = 16476, dbId = 16384}}, rd_rules = 0x0, rd_rulescxt = 0x0, trigdesc = 0x0,
rd_rsdesc = 0x0, rd_fkeylist = 0x0, rd_fkeyvalid = false, rd_partkeycxt = 0x0, rd_partkey = 0x0, rd_pdcxt = 0x0,
rd_partdesc = 0x0, rd_partcheck = 0x0, rd_indexlist = 0x0, rd_oidindex = 0, rd_pkindex = 0, rd_replidindex = 0,
rd_statlist = 0x0, rd_indexattr = 0x0, rd_projindexattr = 0x0, rd_keyattr = 0x0, rd_pkattr = 0x0, rd_idattr = 0x0,
rd_projidx = 0x0, rd_pubactions = 0x0, rd_options = 0x0, rd_index = 0x7f6b9a011898, rd_indextuple = 0x7f6b9a011860,
rd_amhandler = 330, rd_indexcxt = 0x2313400, rd_amroutine = 0x2313530, rd_opfamily = 0x2313640, rd_opcintype = 0x2313658,
rd_support = 0x2313670, rd_supportinfo = 0x2313690, rd_indoption = 0x23137b8, rd_indexprs = 0x0, rd_indpred = 0x0,
rd_exclops = 0x0, rd_exclprocs = 0x0, rd_exclstrats = 0x0, rd_amcache = 0x22fada8, rd_indcollation = 0x23137a0,
rd_fdwroutine = 0x0, rd_toastoid = 0, pgstat_info = 0x22d1230}
(gdb) p *indexRelation->rd_rel
$4 = {relname = {data = "t_dwxx_pkey", '\000' <repeats 52 times>}, relnamespace = 2200, reltype = 0, reloftype = 0,
relowner = 10, relam = 403, relfilenode = 16476, reltablespace = 0, relpages = 2, reltuples = 3, relallvisible = 0,
reltoastrelid = 0, relhasindex = false, relisshared = false, relpersistence = 112 'p', relkind = 105 'i', relnatts = 1,
relchecks = 0, relhasoids = false, relhasrules = false, relhastriggers = false, relhassubclass = false,
relrowsecurity = false, relforcerowsecurity = false, relispopulated = true, relreplident = 110 'n',
relispartition = false, relrewrite = 0, relfrozenxid = 0, relminmxid = 0}
...
#開始構造IndexOptInfo
237 info = makeNode(IndexOptInfo);
(gdb)
239 info->indexoid = index->indexrelid;
(gdb)
241 RelationGetForm(indexRelation)->reltablespace;
(gdb)
240 info->reltablespace =
(gdb)
242 info->rel = rel;
...
(gdb) p index->indnatts
$5 = 1
(gdb) n
246 info->indexkeys = (int *) palloc(sizeof(int) * ncolumns);
(gdb) p index->indnkeyatts
$6 = 1
...
252 for (i = 0; i < ncolumns; i++)
(gdb)
254 info->indexkeys[i] = index->indkey.values[i];
(gdb) p index->indkey.values[i]
$7 = 2
(gdb) p index->indkey
$8 = {vl_len_ = 104, ndim = 1, dataoffset = 0, elemtype = 21, dim1 = 1, lbound1 = 0, values = 0x7f6b9a0118c8}
...
##需結合資料字典檢視
(gdb) p indexRelation->rd_opfamily[i]
$10 = 1994
(gdb) p indexRelation->rd_opcintype[i]
$11 = 25
(gdb) p indexRelation->rd_indcollation[i]
$12 = 100
...
##訪問方法,後續做物理最佳化會使用
(gdb) p indexRelation->rd_rel->relam
$13 = 403
(gdb) p indexRelation->rd_amroutine
$14 = (struct IndexAmRoutine *) 0x2313530
(gdb) p *indexRelation->rd_amroutine
$15 = {type = T_IndexAmRoutine, amstrategies = 5, amsupport = 3, amcanorder = true, amcanorderbyop = false,
amcanbackward = true, amcanunique = true, amcanmulticol = true, amoptionalkey = true, amsearcharray = true,
amsearchnulls = true, amstorage = false, amclusterable = true, ampredlocks = true, amcanparallel = true,
amcaninclude = true, amkeytype = 0, ambuild = 0x4ea341 <btbuild>, ambuildempty = 0x4e282a <btbuildempty>,
aminsert = 0x4e28d0 <btinsert>, ambulkdelete = 0x4e37f0 <btbulkdelete>, amvacuumcleanup = 0x4e397f <btvacuumcleanup>,
amcanreturn = 0x4e427d <btcanreturn>, amcostestimate = 0x94f0ad <btcostestimate>, amoptions = 0x4e9f7f <btoptions>,
amproperty = 0x4e9fa9 <btproperty>, amvalidate = 0x4ecad6 <btvalidate>, ambeginscan = 0x4e2bd8 <btbeginscan>,
amrescan = 0x4e2d54 <btrescan>, amgettuple = 0x4e294f <btgettuple>, amgetbitmap = 0x4e2a7f <btgetbitmap>,
amendscan = 0x4e2f23 <btendscan>, ammarkpos = 0x4e303c <btmarkpos>, amrestrpos = 0x4e310b <btrestrpos>,
amestimateparallelscan = 0x4e3281 <btestimateparallelscan>, aminitparallelscan = 0x4e328c <btinitparallelscan>,
amparallelrescan = 0x4e32da <btparallelrescan>}
##部分屬性值
(gdb) p amroutine->amcanorderbyop
$16 = false
(gdb) p amroutine->amoptionalkey
$17 = true
(gdb) p amroutine->amsearcharray
$18 = true
(gdb) p amroutine->amsearchnulls
$19 = true
(gdb) p amroutine->amcanparallel
$20 = true
##下面是函式指標
(gdb) p *amroutine->amgettuple
$21 = {_Bool (IndexScanDesc, ScanDirection)} 0x4e294f <btgettuple>
(gdb) p *amroutine->amgetbitmap
$24 = {int64 (IndexScanDesc, TIDBitmap *)} 0x4e2a7f <btgetbitmap>
(gdb) p *amroutine->amcostestimate
$26 = {void (struct PlannerInfo *, struct IndexPath *, double, Cost *, Cost *, Selectivity *, double *,
double *)} 0x94f0ad <btcostestimate>
282 if (info->relam == BTREE_AM_OID)
##BTree索引
...
##PK,唯一性為true
(gdb) p index->indisunique
$31 = true
...
(gdb) p info->tree_height
$32 = 0
##第2個索引(函式索引)
183 foreach(l, indexoidlist)
(gdb)
185 Oid indexoid = lfirst_oid(l);
...
進入RelationGetIndexExpressions函式
371 info->indexprs = RelationGetIndexExpressions(indexRelation);
(gdb) step
RelationGetIndexExpressions (relation=0x7f6b9a011970) at relcache.c:4625
##IndexRelation中已有相關資訊
4625 if (relation->rd_indexprs)
(gdb) n
4626 return copyObject(relation->rd_indexprs);
##函式表示式中的args有相關的引數,類似的分析方法先前已有提及
(gdb) p *(FuncExpr *)relation->rd_indexprs->head->data.ptr_value
$36 = {xpr = {type = T_FuncExpr}, funcid = 885, funcresulttype = 25, funcretset = false, funcvariadic = false,
funcformat = COERCE_EXPLICIT_CALL, funccollid = 100, inputcollid = 100, args = 0x22fb638, location = -1}
回到get_relation_info
...
##第3個索引,這是一個部分(條件)索引
183 foreach(l, indexoidlist)
(gdb)
185 Oid indexoid = lfirst_oid(l);
...
372 info->indpred = RelationGetIndexPredicate(indexRelation);
##這是一個OpExpr,詳細的結構先前已有提及
(gdb) p *(Node *)indexRelation->rd_indpred->head->data.ptr_value
$38 = {type = T_OpExpr}
$39 = {xpr = {type = T_OpExpr}, opno = 1209, opfuncid = 850, opresulttype = 16, opretset = false, opcollid = 0,
inputcollid = 100, args = 0x23140d8, location = -1}
...
回到build_simple_rel函式
461 if (get_relation_info_hook)
(gdb)
463 }
(gdb)
build_simple_rel (root=0x23107f8, relid=1, parent=0x0) at relnode.c:185
185 break;
(gdb) n
213 root->simple_rel_array[relid] = rel;
(gdb)
221 if (rte->securityQuals)
(gdb)
231 if (rte->inh)
(gdb)
271 return rel;
(gdb)
272 }
(gdb)
回到add_base_rels_to_query
add_base_rels_to_query (root=0x23107f8, jtnode=0x22515f0) at initsplan.c:133
133 }
##遞迴呼叫完畢,回到FromExpr->fromlist
(gdb) n
add_base_rels_to_query (root=0x23107f8, jtnode=0x2251cc8) at initsplan.c:120
120 foreach(l, f->fromlist)
(gdb) n
133 }
(gdb)
query_planner (root=0x23107f8, tlist=0x2312798, qp_callback=0x76e97d <standard_qp_callback>, qp_extra=0x7ffc7d69a9a0)
at planmain.c:150
150 build_base_rel_tlists(root, tlist);
(gdb)
#DONE!
四、參考資料
planmain.c
rel.h
來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/6906/viewspace-2374871/，如需轉載，請註明出處，否則將追究法律責任。
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