PostgreSQL数据库扩展包——原理get_extension_script_filename扩展SQL文件解析

落日映苍穹つ 2022-10-13 01:59 201阅读 0赞

filename = get_extension_script_filename(pcontrol, NULL, versionName);

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get\_extension\_script\_directory函数获取sharepath/control->directory目录，get\_extension\_script\_filename函数获取：

*  from\_version为NULL，返回sharepath/control->directory/control->name–version.sql
 *  from\_version不为NULL，返回sharepath/control->directory/control->name–from\_version–version.sql  
    get\_extension\_script\_filename获取sql文件名，规则如下：  
    版本命名的规则:扩展名 +“–”+“版本号”+ .sql (eg:cube–1.2.sql)  
    版本与版本之间的升级采用“–”连接。(eg:cube–1.2–1.3.sql)  
    Target 版本由控制文件中的default\_version确定。  
    根据目标版本选择最短路径。

static char *get_extension_script_filename(ExtensionControlFile *control, const char *from_version, const char *version) { 
    	char	   *result;
    	char	   *scriptdir;
    	scriptdir = get_extension_script_directory(control);
    	result = (char *) palloc(MAXPGPATH);
    	if (from_version)
    		snprintf(result, MAXPGPATH, "%s/%s--%s--%s.sql", scriptdir, control->name, from_version, version);
    	else
    		snprintf(result, MAXPGPATH, "%s/%s--%s.sql", scriptdir, control->name, version);
    	pfree(scriptdir);
    	return result;
    }
    
    static char *get_extension_script_directory(ExtensionControlFile *control) { 
    	char		sharepath[MAXPGPATH];
    	char	   *result;
    	/* The directory parameter can be omitted, absolute, or relative to the installation's share directory. */
    	if (!control->directory)	return get_extension_control_directory();
    	if (is_absolute_path(control->directory))	return pstrdup(control->directory);
    	get_share_path(my_exec_path, sharepath);
    	result = (char *) palloc(MAXPGPATH);
    	snprintf(result, MAXPGPATH, "%s/%s", sharepath, control->directory);
    	return result;
    }

调用get\_extension\_script\_filename函数后，后续处理如下：

1.  get\_ext\_ver\_list()：遍历所有.sql文件获取所有版本节点。
2.  find\_install\_path()：根据目标节点选择最短路径以及相对应的起始节点。
3.  find\_update\_path()：最短路径算法Dijkstra的实现。

filename = get_extension_script_filename(pcontrol, NULL, versionName);
    			/* Look for best way to install this version */
    			List	   *evi_list;
    			ExtensionVersionInfo *evi_start;
    			ExtensionVersionInfo *evi_target;
    			/* Extract the version update graph from the script directory */
    			evi_list = get_ext_ver_list(pcontrol);
    			/* Identify the target version */
    			evi_target = get_ext_ver_info(versionName, &evi_list);
    			/* Identify best path to reach target */
    			evi_start = find_install_path(evi_list, evi_target, &updateVersions);
    			/* Fail if no path ... */
    			if (evi_start == NULL) ereport(ERROR,(errcode(ERRCODE_INVALID_PARAMETER_VALUE),errmsg("extension \"%s\" has no installation script nor update path for version \"%s\"",pcontrol->name, versionName)));
    			/* Otherwise, install best starting point and then upgrade */
    			versionName = evi_start->name;

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