openGauss内核分析(九):数据库表的创建过程

joytrian
发布于 2023-5-5 11:00
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除了DML之外的所有查询都通过ProcessUtility模块来执行,包括了各类DDL语句、事务相关语句、游标相关语句等。上层调用函数为exec_simple_query函数,其中PortalStart函数和PortalDrop函数部分较为简单。核心函数是PortalRun函数下层调用的standard_ProcessUtility函数,该函数通过switch case语句处理了各种类型的查询语句,包括事务相关查询、游标相关查询、schema相关操作、表空间相关操作、表定义相关操作等。

standard_ProcessUtility函数会根据nodeTag(parsetree)的值来确定sql的操作类型,create table一般都是进入T_CreateStmt分支,调用CreateCommand函数。

void standard_ProcessUtility(Node* parse_tree, const char* query_string, ParamListInfo params, bool is_top_level,
    DestReceiver* dest,
#ifdef PGXC
    bool sent_to_remote,
#endif /* PGXC */
    char* completion_tag,
    bool isCTAS)
{
……
    errno_t errorno = EOK;
switch (nodeTag(parse_tree)) { // 根据nodeTag(parsetree)的值来确定sql的操作类型
……
        case T_CreateStmt: { // create table
#ifdef PGXC
            CreateCommand((CreateStmt*)parse_tree, query_string, params, is_top_level, sent_to_remote, isCTAS);
#else
            CreateCommand((CreateStmt*)parse_tree, query_string, params, is_top_level, isCTAS);
#endif
        } break;
……

openGauss内核分析(九):数据库表的创建过程-鸿蒙开发者社区

CreateCommand函数先解析parse_tree获取stmt,如果stmt为空则表明表已经存在。如果stmt不为空对stmts进行遍历,如果是 CreateStmt就调用DefineRelation。AlterTableCreateToastTable判断是否需要创建toast表并创建,AlterCStoreCreateTables判断是否需要创建列存表并创建。

#ifdef PGXC
void CreateCommand(CreateStmt *parse_tree, const char *query_string, ParamListInfo params,
                   bool is_top_level, bool sent_to_remote, bool isCTAS)
#else
void CreateCommand(CreateStmt *parse_tree, const char *query_string, ParamListInfo params, bool is_top_level,
    bool isCTAS)
#endif
{
……
    /* Run parse analysis ... */
    if (u_sess->attr.attr_sql.enable_parallel_ddl) // 先解析parse_tree获取stmt
        stmts = transformCreateStmt((CreateStmt*)parse_tree, query_string, NIL, true, &namespace_id, is_first_node);
    else
        stmts = transformCreateStmt((CreateStmt*)parse_tree, query_string, NIL, false, &namespace_id);

    /*
     * If stmts is NULL, then the table is exists.
     * we need record that for searching the group of table.
     */
    if (stmts == NIL) { // 如果stmt为空则表明表已经存在
        table_is_exist = true;
……
    /* ... and do it */
    foreach (l, stmts) { // 遍历stmts
        Node* stmt = (Node*)lfirst(l);

        if (IsA(stmt, CreateStmt)) {  // 如果是 CreateStmt就调用DefineRelation
            Datum toast_options;
            static const char* const validnsps[] = HEAP_RELOPT_NAMESPACES;
           
            /* forbid user to set or change inner options */
            ForbidOutUsersToSetInnerOptions(((CreateStmt*)stmt)->options);
            
            /* Create the table itself */
            rel_oid = DefineRelation((CreateStmt*)stmt,
                                    ((CreateStmt*)stmt)->relkind == RELKIND_MATVIEW ?
                                                                    
RELKIND_MATVIEW : RELKIND_RELATION,                                                                    
                                    InvalidOid, isCTAS);
……
            AlterTableCreateToastTable(rel_oid, toast_options, AccessShareLock);
            AlterCStoreCreateTables(rel_oid, toast_options, (CreateStmt*)stmt);
            AlterDfsCreateTables(rel_oid, toast_options, (CreateStmt*)stmt);
            AlterCreateChainTables(rel_oid, toast_options, (CreateStmt *)stmt);
……

DefineRelation函数获取到表名relname、名字空间relnamespace、表空间reltablespace、表类型relkind和relpersistence等信息后调用heap_create_with_catalog创建relation。

(gdb) f 0
#0  heap_create_with_catalog (relname=0x7fb4fa872140 "t100", relnamespace=2200, reltablespace=0, relid=0, reltypeid=0,
    reloftypeid=0, ownerid=10, tupdesc=0x7fb4ff2e2e50, cooked_constraints=0x0, relkind=114 'r', relpersistence=112 'p',
    shared_relation=false, mapped_relation=false, oidislocal=false, oidinhcount=0, oncommit=ONCOMMIT_NOOP,
    reloptions=140415352057720, use_user_acl=true, allow_system_table_mods=false, partTableState=0x0, row_compress=1 '\001',
    bucketinfo=0x0, record_dependce=true, ceLst=0x0, storage_type=HEAP_DISK, partLockMode=1) at heap.cpp:2521

其中heap_create内部首先调用了RelationBuildLocalRelation创建RelationData,并加入到relCache,RelationData表示一个表的元信息,这些信息都可以由系统表元组中的信息构造得到。然后根据这些信息通过调用RelalionCreateStorage函数创建物理文件。heap_create_with_catalog主要完成表物理文件的创建和表元信息注册到系统表中,涉及系统包包括pg_class,pg_attribute,pg_depend,pg_object,pg_type,pg_index和pg_partition

openGauss内核分析(九):数据库表的创建过程-鸿蒙开发者社区

创建表create table的函数调用栈

#0  RelationCreateStorage
#1  heap_create
#2  heap_create_with_catalog
#3  DefineRelation
#4  CreateCommand
#5  standard_ProcessUtility
#6  gsaudit_ProcessUtility_hook
#7  pgaudit_ProcessUtility
#8  hypo_utility_hook
#9  ProcessUtility
#10 PortalRunUtility
#11 PortalRunMulti
#12 PortalRun
#13 exec_simple_query
#14 PostgresMain

文章转载自公众号:openGauss

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