pg_orphaned扩展分析（一）

/* 忽略文件名非数字的文件 */if (strstr(de->d_name, "_") ==NULL&&isdigit((unsignedchar) *(de->d_name))) {
orph=palloc(sizeof(*orph));
relfilename=strdup(de->d_name);
relfilenode= (Oid) strtoul(relfilename, &relfilename, 10);
/* 如果RelidByRelfilenodeDirty没有返回有效的oid* 我们就认为此文件是个孤儿文件*/oidrel=RelidByRelfilenodeDirty(reltablespace, relfilenode);
/*           * 如果是指定relation的第一个segment文件、大小为0并且是在上一次checkpoint之后创建的文件* 我们过滤之并不做为孤儿文件上报* due to https://github.com/postgres/postgres/blob/REL_12_8/src/backend/storage/smgr/md.c#L225*/segment_time=time_t_to_timestamptz(attrib.st_mtime);
if (!OidIsValid(oidrel) &&!(attrib.st_size==0&&strstr(de->d_name, ".") ==NULL&&segment_time>last_checkpoint_time))
            {
orph->dbname=strdup(dbname);
orph->path=strdup(dir);
orph->name=strdup(de->d_name);
orph->size= (int64) attrib.st_size;
orph->mod_time=segment_time;
orph->relfilenode=relfilenode;
orph->reloid=oidrel;
*flist=lappend(*flist, orph);
/* search for _init and _fsm */if(strstr(de->d_name, ".") ==NULL)
pgorph_add_suffix(flist, orph);
            }       
        }

/* get a copy of the control file */#if PG_VERSION_NUM >= 120000ControlFile=get_controlfile(".", &crc_ok);
#elseControlFile=get_controlfile(".", NULL, &crc_ok);
#endifif (!crc_ok)
ereport(ERROR,(errmsg("pg_control CRC value is incorrect")));
/* get last checkpoint time */time_tmp= (time_t) ControlFile->checkPointCopy.time;
last_checkpoint_time=time_t_to_timestamptz(time_tmp);

/** Map a relation's (tablespace, filenode) to a relation's oid and cache the* result.** This is the same as the existing RelidByRelfilenode in relfilenodemap.c but* it is done by using a DirtySnapshot as we want to see relation being created.** Returns InvalidOid if no relation matching the criteria could be found.*/OidRelidByRelfilenodeDirty(Oidreltablespace, Oidrelfilenode){...}

else    {
/** Not a shared table, could either be a plain relation or a* non-shared, nailed one, like e.g. pg_class.*//* check for plain relations by looking in pg_class */#if PG_VERSION_NUM >= 120000/** RelationRelationId在pg_class_d.h中定义* 值为1259，pg_class的OID* 所以这里打开pg_class*/relation=table_open(RelationRelationId, AccessShareLock);
#elserelation=heap_open(RelationRelationId, AccessShareLock);
#endif/* copy scankey to local copy, it will be modified during the scan *//* relfilenode_skey_dirty的解释见下文 */memcpy(skey, relfilenode_skey_dirty, sizeof(skey));
/* 设置扫描参数 */skey[0].sk_argument=ObjectIdGetDatum(reltablespace);
skey[1].sk_argument=ObjectIdGetDatum(relfilenode);
scandesc=systable_beginscan(relation,
ClassTblspcRelfilenodeIndexId,
true,
&DirtySnapshot,
2,
skey);
found=false;
while (HeapTupleIsValid(ntp=systable_getnext(scandesc)))
        {
#if PG_VERSION_NUM >= 120000Form_pg_classclassform= (Form_pg_class) GETSTRUCT(ntp);
found=true;
Assert(classform->reltablespace==reltablespace);
Assert(classform->relfilenode==relfilenode);
relid=classform->oid;
#elsefound=true;
relid=HeapTupleGetOid(ntp);
#endif        }
systable_endscan(scandesc);
#if PG_VERSION_NUM >= 120000table_close(relation, AccessShareLock);
#elseheap_close(relation, AccessShareLock);
#endif/* check for tables that are mapped but not shared */if (!found)
#if PG_VERSION_NUM >= 160000relid=RelationMapFilenumberToOid(relfilenode, false);
#elserelid=RelationMapFilenodeToOid(relfilenode, false);
#endif    }
/** Only enter entry into cache now, our opening of pg_class could have* caused cache invalidations to be executed which would have deleted a* new entry if we had entered it above.*/entry=hash_search(RelfilenodeMapHashDirty, (void*) &key, HASH_ENTER, &found);
if (found)
elog(ERROR, "corrupted hashtable");
entry->relid=relid;

/** Initialize cache, either on first use or after a reset.* Same as InitializeRelfilenodeMap in relfilenodemap.c*/staticvoidInitializeRelfilenodeMapDirty(void)
{
HASHCTLctl;
inti;
/* 确保我们已经初始化了CacheMemoryContext. */if (CacheMemoryContext==NULL)
CreateCacheMemoryContext();
/* 构造skey */MemSet(&relfilenode_skey_dirty, 0, sizeof(relfilenode_skey_dirty));
/* 我们搜索pg_class时使用了两个键值，tablespace和filenode，所以这里是2 */for (i=0; i<2; i++)
    {
/* 填充FmgrInfo结构 */fmgr_info_cxt(F_OIDEQ,
&relfilenode_skey_dirty[i].sk_func,
CacheMemoryContext);
/* 使用Btree索引相等策略 */relfilenode_skey_dirty[i].sk_strategy=BTEqualStrategyNumber;
relfilenode_skey_dirty[i].sk_subtype=InvalidOid;
relfilenode_skey_dirty[i].sk_collation=InvalidOid;
    }
/* 设置查找键值 */relfilenode_skey_dirty[0].sk_attno=Anum_pg_class_reltablespace;
relfilenode_skey_dirty[1].sk_attno=Anum_pg_class_relfilenode;
/* 初始化hash表 */MemSet(&ctl, 0, sizeof(ctl));
ctl.keysize=sizeof(RelfilenodeMapKeyDirty);
ctl.entrysize=sizeof(RelfilenodeMapEntryDirty);
/* hash表位于CacheMemoryContext */ctl.hcxt=CacheMemoryContext;
/** Only create the RelfilenodeMapHashDirty now, so we don't end up partially* initialized when fmgr_info_cxt() above ERRORs out with an out of memory* error.* Note that the hash table is not created in shared memory but in* private memory.*/RelfilenodeMapHashDirty=hash_create("RelfilenodeMap cache", 64, &ctl,
HASH_ELEM|HASH_BLOBS|HASH_CONTEXT);
/* Watch for invalidation events. */CacheRegisterRelcacheCallback(RelfilenodeMapInvalidateCallbackDirty,
                                    (Datum) 0);
}

typedefstruct{
Oidreltablespace;
Oidrelfilenode;
} RelfilenodeMapKeyDirty;
typedefstruct{
RelfilenodeMapKeyDirtykey;          /* lookup key - must be first */Oidrelid;                  /* pg_class.oid */} RelfilenodeMapEntryDirty;

HTAB*hash_create(constchar*tabname, longnelem, constHASHCTL*info, intflags);
void*hash_search(HTAB*hashp,
constvoid*keyPtr,
HASHACTIONaction,
bool*foundPtr)

/* Hash table for information about each relfilenode <-> oid pair */staticHTAB*RelfilenodeMapHashDirty=NULL;
HASHCTLctl;
/* 初始化hash表 */MemSet(&ctl, 0, sizeof(ctl));
ctl.keysize=sizeof(RelfilenodeMapKeyDirty);
ctl.entrysize=sizeof(RelfilenodeMapEntryDirty);
/* hash表位于CacheMemoryContext */ctl.hcxt=CacheMemoryContext;
RelfilenodeMapHashDirty=hash_create("RelfilenodeMap cache", 64, &ctl,
HASH_ELEM|HASH_BLOBS|HASH_CONTEXT);
/* hash_search */RelfilenodeMapEntryDirty*entry;
entry=hash_search(RelfilenodeMapHashDirty, (void*) &key, HASH_FIND, &found);