Postgresql源码（48）namespace计算逻辑分析（不显示指定namespace）

postgres=# show search_path ;
   search_path   
-----------------
 "$user", public

-- 优先级1：临时表
-- create temp table pg_class(i int);
pg_temp_3.pg_class

-- 优先级2：pg_catalog
pg_catalog.pg_class

-- 优先级3：普通表
-- create table pg_class(a int);
public.pg_class

		activeSearchPath = baseSearchPath;
		activeCreationNamespace = baseCreationNamespace;
		activeTempCreationPending = baseTempCreationPending;

	activeSearchPath = entry->searchPath;
	activeCreationNamespace = entry->creationNamespace;
	activeTempCreationPending = false;	/* XXX is this OK? */

activeSearchPath
(gdb) p activeSearchPath->elements[0]->oid_value
$9 = 24709
(gdb) p activeSearchPath->elements[1]->oid_value
$10 = 11
(gdb) p activeSearchPath->elements[2]->oid_value
$11 = 2200

(gdb) p baseSearchPath->elements[0]->oid_value
$14 = 24709
(gdb) p baseSearchPath->elements[1]->oid_value
$15 = 11
(gdb) p baseSearchPath->elements[2]->oid_value
$16 = 2200

static void
recomputeNamespacePath(void)
{
  ...

// overrideStack优先级最高，有的话直接使用，不做任何更新
	if (overrideStack)
		return;

//【1】
	if (baseSearchPathValid && namespaceUser == roleid)
		return;

// $2 = 0x28125a0 "\"$user\", public"
	rawname = pstrdup(namespace_search_path);

//【2】
// p (char*)namelist->elements[0]->ptr_value
// $11 = 0x28125a1 "$user"
// p (char*)namelist->elements[1]->ptr_value
// $12 = 0x28125a9 "public"
	SplitIdentifierString(rawname, ',', &namelist)
  ...

  // 解析List的结果集
	oidlist = NIL;
	temp_missing = false;
	foreach(l, namelist)
  /*
    (gdb) p (char*)namelist->elements[0]->ptr_value
    $22 = 0x28125a1 "$user"
    (gdb) p (char*)namelist->elements[1]->ptr_value
    $23 = 0x28125a9 "public"
  */
	{
		char	   *curname = (char *) lfirst(l);
		Oid			namespaceId;

		if (strcmp(curname, "$user") == 0)
		{
			HeapTuple	tuple;

			tuple = SearchSysCache1(AUTHOID, ObjectIdGetDatum(roleid));
			if (HeapTupleIsValid(tuple))
			{
				char	   *rname;
        // 查系统表pg_authid，查到了，确实有这个用户
				rname = NameStr(((Form_pg_authid) GETSTRUCT(tuple))->rolname);
        
        // 用户名mingjiegao去pg_namespace里面查不到！
        // namespaceId = 0
				namespaceId = get_namespace_oid(rname, true);
				ReleaseSysCache(tuple);
				// 先做权限检查acl check ...
        // 【3】记录到结果中，注意只记录OID即可
				oidlist = lappend_oid(oidlist, namespaceId);
			}
		}
		else if (strcmp(curname, "pg_temp") == 0)
		{
			if (OidIsValid(myTempNamespace))
			{
				if (!list_member_oid(oidlist, myTempNamespace) &&
					InvokeNamespaceSearchHook(myTempNamespace, false))
					oidlist = lappend_oid(oidlist, myTempNamespace);
			}
			else
			{
				/* If it ought to be the creation namespace, set flag */
				if (oidlist == NIL)
					temp_missing = true;
			}
		}
		else
		{
			// 【4】给了一个普通的字符串，表示namespace，这里查pg_namespace
			namespaceId = get_namespace_oid(curname, true);
			if (OidIsValid(namespaceId) &&
				!list_member_oid(oidlist, namespaceId) &&
				pg_namespace_aclcheck(namespaceId, roleid,
									  ACL_USAGE) == ACLCHECK_OK &&
				InvokeNamespaceSearchHook(namespaceId, false))
        // 在系统表中确有指定名称，oid记录到结果中
				oidlist = lappend_oid(oidlist, namespaceId);
		}
	}

  // 记录第一个解析出来的oid
  // public 2200
	if (oidlist == NIL)
		firstNS = InvalidOid;
	else
		firstNS = linitial_oid(oidlist);
  
  // 【5】把PG_CATALOG加到最前面
  //  (gdb) p oidlist->elements[0]->oid_value
  // $16 = 11
	if (!list_member_oid(oidlist, PG_CATALOG_NAMESPACE))
		oidlist = lcons_oid(PG_CATALOG_NAMESPACE, oidlist);

  // 【6】把私有tmp表空间加到最前面
  // （如果有）
	if (OidIsValid(myTempNamespace) &&
		!list_member_oid(oidlist, myTempNamespace))
		oidlist = lcons_oid(myTempNamespace, oidlist);

  // 如果值都是正确的，不在进行重新赋值，避免值拷贝
	if (baseCreationNamespace == firstNS &&
		baseTempCreationPending == temp_missing &&
		equal(oidlist, baseSearchPath))
	{
		pathChanged = false;
	}
	else
	{
    //【7】三个全局变量赋值：baseSearchPath就是上面拼接的oidlist、baseCreationNamespace=第一个nsoid
		pathChanged = true;

		/* Must save OID list in permanent storage. */
		oldcxt = MemoryContextSwitchTo(TopMemoryContext);
		newpath = list_copy(oidlist);
		MemoryContextSwitchTo(oldcxt);

		/* Now safe to assign to state variables. */
		list_free(baseSearchPath);
		baseSearchPath = newpath;
		baseCreationNamespace = firstNS;
		baseTempCreationPending = temp_missing;
	}

	/* Mark the path valid. */
	baseSearchPathValid = true;
	namespaceUser = roleid;

	//【8】上面计算完了，真正激活使用是在这里。
  // 其他工具函数只会用active的值。
	activeSearchPath = baseSearchPath;
	activeCreationNamespace = baseCreationNamespace;
	activeTempCreationPending = baseTempCreationPending;

	/*
	 * Bump the generation only if something actually changed.  (Notice that
	 * what we compared to was the old state of the base path variables; so
	 * this does not deal with the situation where we have just popped an
	 * override path and restored the prior state of the base path.  Instead
	 * we rely on the override-popping logic to have bumped the generation.)
	 */
	if (pathChanged)
		activePathGeneration++;

	/* Clean up. */
	pfree(rawname);
	list_free(namelist);
	list_free(oidlist);
}

(gdb) p *newRelation
$20 = {type = T_RangeVar, catalogname = 0x0, schemaname = 0x0, relname = 0x2811ed8 "sss", inh = true, relpersistence = 112 'p', alias = 0x0, location = 13}

Oid
RangeVarGetCreationNamespace(const RangeVar *newRelation)
{
	Oid			namespaceId;

	/*
	 * We check the catalog name and then ignore it.
	 */
	if (newRelation->catalogname)
	{
		if (strcmp(newRelation->catalogname, get_database_name(MyDatabaseId)) != 0)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cross-database references are not implemented: \"%s.%s.%s\"",
							newRelation->catalogname, newRelation->schemaname,
							newRelation->relname)));
	}

	if (newRelation->schemaname)
	{
...
	}
	else if (newRelation->relpersistence == RELPERSISTENCE_TEMP)
	{
...
	}
	else
	{
		/* use the default creation namespace */
		recomputeNamespacePath();
		if (activeTempCreationPending)
		{
			/* Need to initialize temp namespace */
			AccessTempTableNamespace(true);
			return myTempNamespace;
		}
		namespaceId = activeCreationNamespace;
		if (!OidIsValid(namespaceId))
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_SCHEMA),
					 errmsg("no schema has been selected to create in")));
	}

	/* Note: callers will check for CREATE rights when appropriate */

	return namespaceId;
}