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pgtrashcan.c
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pgtrashcan.c
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#include <postgres.h>
#if PG_VERSION_NUM >= 90300
#include <access/htup_details.h>
#endif
#include <access/xact.h>
#include <catalog/namespace.h>
#include <catalog/pg_database.h>
#include <catalog/pg_namespace.h>
#include <miscadmin.h>
#include <tcop/utility.h>
#include <utils/rel.h>
#include <utils/syscache.h>
PG_MODULE_MAGIC;
static ProcessUtility_hook_type prev_ProcessUtility = NULL;
#if PG_VERSION_NUM >= 90300
static void pgtrashcan_ProcessUtility(Node *parsetree,
const char *queryString,
ProcessUtilityContext context,
ParamListInfo params,
DestReceiver *dest,
char *completionTag);
#else
static void pgtrashcan_ProcessUtility(Node *parsetree,
const char *queryString,
ParamListInfo params,
bool isTopLevel,
DestReceiver *dest,
char *completionTag);
#endif
static const char *trashcan_nspname = "Trash";
void _PG_init(void);
void
_PG_init(void)
{
prev_ProcessUtility = ProcessUtility_hook;
if (!prev_ProcessUtility)
prev_ProcessUtility = standard_ProcessUtility;
ProcessUtility_hook = pgtrashcan_ProcessUtility;
}
static RangeVar *
makeRangeVarFromAnyName(List *names)
{
RangeVar *r = makeNode(RangeVar);
switch (list_length(names))
{
case 1:
r->catalogname = NULL;
r->schemaname = NULL;
r->relname = strVal(linitial(names));
break;
case 2:
r->catalogname = NULL;
r->schemaname = strVal(linitial(names));
r->relname = strVal(lsecond(names));
break;
case 3:
r->catalogname = strVal(linitial(names));;
r->schemaname = strVal(lsecond(names));
r->relname = strVal(lthird(names));
break;
default:
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("improper qualified name (too many dotted names): %s",
NameListToString(names))));
break;
}
#if PG_VERSION_NUM >= 90100
r->relpersistence = RELPERSISTENCE_PERMANENT;
#endif
r->location = -1;
return r;
}
static void
create_trashcan_schema(void)
{
HeapTuple tuple;
Oid datdba;
if (SearchSysCacheExists1(NAMESPACENAME, PointerGetDatum(trashcan_nspname)))
return;
tuple = SearchSysCache1(DATABASEOID, ObjectIdGetDatum(MyDatabaseId));
if (!HeapTupleIsValid(tuple))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database with OID %u does not exist", MyDatabaseId)));
datdba = ((Form_pg_database) GETSTRUCT(tuple))->datdba;
ReleaseSysCache(tuple);
NamespaceCreate(trashcan_nspname, datdba, false);
CommandCounterIncrement();
}
#if PG_VERSION_NUM >= 90300
static void
pgtrashcan_ProcessUtility(Node *parsetree,
const char *queryString,
ProcessUtilityContext context,
ParamListInfo params,
DestReceiver *dest,
char *completionTag)
#else
static void
pgtrashcan_ProcessUtility(Node *parsetree,
const char *queryString,
ParamListInfo params,
bool isTopLevel,
DestReceiver *dest,
char *completionTag)
#endif
{
if (nodeTag(parsetree) == T_DropStmt)
{
DropStmt *stmt = (DropStmt *) parsetree;
if (stmt->removeType == OBJECT_TABLE)
{
RangeVar *r;
AlterObjectSchemaStmt *newstmt = makeNode(AlterObjectSchemaStmt);
newstmt->objectType = stmt->removeType;
newstmt->newschema = pstrdup(trashcan_nspname);
#if PG_VERSION_NUM >= 90200
newstmt->missing_ok = stmt->missing_ok;
#endif
if (stmt->behavior != DROP_RESTRICT)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("trash can does not support DROP CASCADE")));
r = makeRangeVarFromAnyName(linitial(stmt->objects));
r->inhOpt = INH_YES;
r->alias = NULL;
newstmt->relation = r;
if (!r->schemaname || strcmp(r->schemaname, trashcan_nspname) != 0)
{
parsetree = (Node *) newstmt;
create_trashcan_schema();
}
}
}
#if PG_VERSION_NUM >= 90300
(*prev_ProcessUtility) (parsetree, queryString, context, params, dest, completionTag);
#else
(*prev_ProcessUtility) (parsetree, queryString, params, isTopLevel, dest, completionTag);
#endif
}