src/backend/commands/schemacmds.c:52-248
CreateSchemaCommand implements the CREATE SCHEMA SQL command, creating a new database schema and executing any embedded SQL statements within the schema creation context.
Oid
CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString,
int stmt_location, int stmt_len)CreateSchemaCommand orchestrates the complete CREATE SCHEMA operation, handling authorization, namespace creation, and execution of embedded statements. The function performs comprehensive security checks, creates the schema namespace, temporarily modifies the search path to include the new schema, and processes any embedded SQL statements (like CREATE TABLE, CREATE VIEW) within the schema context.
Key behaviors include:
- Resolving the schema owner (either specified or defaulting to current user)
- Performing ACL checks for database CREATE privilege and role ownership
- Handling IF NOT EXISTS logic with extension membership validation
- Creating the actual namespace through NamespaceCreate
- Temporarily prepending the new schema to search_path during embedded statement execution
- Processing embedded statements in dependency-resolved order
- Proper cleanup of security context and GUC settings
*stmt: CreateSchemaStmt containing schema name, owner role spec, IF NOT EXISTS flag, and embedded statement list*queryString: Original SQL query string for error reporting and loggingstmt_location: Character offset of the statement in the query stringstmt_len: Length of the statement in characters
- Functions called/Symbols referenced:
- NamespaceCreate (creates the actual namespace)
- GetUserIdAndSecContext/SetUserIdAndSecContext (security context management)
- get_rolespec_oid (resolves owner role specification)
- object_aclcheck (checks CREATE privilege on database)
- checkMembershipInCurrentExtension (validates extension membership for IF NOT EXISTS)
- transformCreateSchemaStmtElements (reorganizes embedded statements)
- ProcessUtility (executes embedded statements)
- EventTriggerCollectSimpleCommand (reports schema creation to event triggers)
- Called from (representative examples):
- ProcessUtilitySlow (main utility command processing)
- CreateExtensionInternal (schema creation during extension installation)
- Returns the OID of the created namespace, or InvalidOid if skipped due to IF NOT EXISTS
- Temporarily modifies search_path to include the new schema during embedded statement execution
- Uses function-level SET to ensure search_path changes persist only for the duration of schema creation
- Validates against reserved schema names (pg_* prefix) unless allowSystemTableMods is enabled
- Handles ownership transfer by temporarily switching user context during creation
- Location information is passed through to embedded statements for consistent error reporting
Oid CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString,
int stmt_location, int stmt_len)
{
const char *schemaName = stmt->schemaname;
Oid namespaceId;
Oid owner_uid, saved_uid;
int save_sec_context, save_nestlevel;
// Get current security context
GetUserIdAndSecContext(&saved_uid, &save_sec_context);
// Determine schema owner (specified role or current user)
if (stmt->authrole)
owner_uid = get_rolespec_oid(stmt->authrole, false);
else
owner_uid = saved_uid;
// Use owner's name as schema name if not specified
if (!schemaName) {
HeapTuple tuple = SearchSysCache1(AUTHOID, ObjectIdGetDatum(owner_uid));
schemaName = pstrdup(NameStr(((Form_pg_authid) GETSTRUCT(tuple))->rolname));
ReleaseSysCache(tuple);
}
// Check permissions: CREATE privilege on database and role ownership
if (object_aclcheck(DatabaseRelationId, MyDatabaseId, saved_uid, ACL_CREATE) != ACLCHECK_OK)
aclcheck_error(ACLCHECK_NO_PRIV, OBJECT_DATABASE, get_database_name(MyDatabaseId));
check_can_set_role(saved_uid, owner_uid);
// Prevent creation of reserved schema names (pg_*)
if (!allowSystemTableMods && IsReservedName(schemaName))
ereport(ERROR, (errcode(ERRCODE_RESERVED_NAME),
errmsg("unacceptable schema name \"%s\"", schemaName)));
// Handle IF NOT EXISTS - skip if schema already exists
if (stmt->if_not_exists) {
namespaceId = get_namespace_oid(schemaName, true);
if (OidIsValid(namespaceId)) {
// Validate extension membership for security
ObjectAddress address;
ObjectAddressSet(address, NamespaceRelationId, namespaceId);
checkMembershipInCurrentExtension(&address);
return InvalidOid; // Skip creation
}
}
// Switch to target owner's security context if different
if (saved_uid != owner_uid)
SetUserIdAndSecContext(owner_uid, save_sec_context | SECURITY_LOCAL_USERID_CHANGE);
// Create the schema namespace
namespaceId = NamespaceCreate(schemaName, owner_uid, false);
CommandCounterIncrement();
// Temporarily add new schema to search_path for embedded statements
save_nestlevel = NewGUCNestLevel();
StringInfoData pathbuf;
initStringInfo(&pathbuf);
appendStringInfoString(&pathbuf, quote_identifier(schemaName));
appendStringInfo(&pathbuf, ", %s", namespace_search_path);
set_config_option("search_path", pathbuf.data, PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0, false);
// Report schema creation to event triggers
ObjectAddress address;
ObjectAddressSet(address, NamespaceRelationId, namespaceId);
EventTriggerCollectSimpleCommand(address, InvalidObjectAddress, (Node *) stmt);
// Process embedded statements (CREATE TABLE, etc.) in correct order
List *parsetree_list = transformCreateSchemaStmtElements(stmt->schemaElts, schemaName);
ListCell *parsetree_item;
foreach(parsetree_item, parsetree_list) {
Node *embedded_stmt = (Node *) lfirst(parsetree_item);
// Wrap statement for ProcessUtility
PlannedStmt *wrapper = makeNode(PlannedStmt);
wrapper->commandType = CMD_UTILITY;
wrapper->canSetTag = false;
wrapper->utilityStmt = embedded_stmt;
wrapper->stmt_location = stmt_location;
wrapper->stmt_len = stmt_len;
// Execute embedded statement
ProcessUtility(wrapper, queryString, false, PROCESS_UTILITY_SUBCOMMAND,
NULL, NULL, None_Receiver, NULL);
CommandCounterIncrement();
}
// Restore search_path and security context
AtEOXact_GUC(true, save_nestlevel);
SetUserIdAndSecContext(saved_uid, save_sec_context);
return namespaceId;
}