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-rw-r--r--src/backend/commands/comment.c459
1 files changed, 459 insertions, 0 deletions
diff --git a/src/backend/commands/comment.c b/src/backend/commands/comment.c
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+/*-------------------------------------------------------------------------
+ *
+ * comment.c
+ *
+ * PostgreSQL object comments utility code.
+ *
+ * Copyright (c) 1996-2023, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ * src/backend/commands/comment.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/genam.h"
+#include "access/htup_details.h"
+#include "access/relation.h"
+#include "access/table.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaddress.h"
+#include "catalog/pg_description.h"
+#include "catalog/pg_shdescription.h"
+#include "commands/comment.h"
+#include "commands/dbcommands.h"
+#include "miscadmin.h"
+#include "utils/builtins.h"
+#include "utils/fmgroids.h"
+#include "utils/rel.h"
+
+
+/*
+ * CommentObject --
+ *
+ * This routine is used to add the associated comment into
+ * pg_description for the object specified by the given SQL command.
+ */
+ObjectAddress
+CommentObject(CommentStmt *stmt)
+{
+ Relation relation;
+ ObjectAddress address = InvalidObjectAddress;
+
+ /*
+ * When loading a dump, we may see a COMMENT ON DATABASE for the old name
+ * of the database. Erroring out would prevent pg_restore from completing
+ * (which is really pg_restore's fault, but for now we will work around
+ * the problem here). Consensus is that the best fix is to treat wrong
+ * database name as a WARNING not an ERROR; hence, the following special
+ * case.
+ */
+ if (stmt->objtype == OBJECT_DATABASE)
+ {
+ char *database = strVal(stmt->object);
+
+ if (!OidIsValid(get_database_oid(database, true)))
+ {
+ ereport(WARNING,
+ (errcode(ERRCODE_UNDEFINED_DATABASE),
+ errmsg("database \"%s\" does not exist", database)));
+ return address;
+ }
+ }
+
+ /*
+ * Translate the parser representation that identifies this object into an
+ * ObjectAddress. get_object_address() will throw an error if the object
+ * does not exist, and will also acquire a lock on the target to guard
+ * against concurrent DROP operations.
+ */
+ address = get_object_address(stmt->objtype, stmt->object,
+ &relation, ShareUpdateExclusiveLock, false);
+
+ /* Require ownership of the target object. */
+ check_object_ownership(GetUserId(), stmt->objtype, address,
+ stmt->object, relation);
+
+ /* Perform other integrity checks as needed. */
+ switch (stmt->objtype)
+ {
+ case OBJECT_COLUMN:
+
+ /*
+ * Allow comments only on columns of tables, views, materialized
+ * views, composite types, and foreign tables (which are the only
+ * relkinds for which pg_dump will dump per-column comments). In
+ * particular we wish to disallow comments on index columns,
+ * because the naming of an index's columns may change across PG
+ * versions, so dumping per-column comments could create reload
+ * failures.
+ */
+ if (relation->rd_rel->relkind != RELKIND_RELATION &&
+ relation->rd_rel->relkind != RELKIND_VIEW &&
+ relation->rd_rel->relkind != RELKIND_MATVIEW &&
+ relation->rd_rel->relkind != RELKIND_COMPOSITE_TYPE &&
+ relation->rd_rel->relkind != RELKIND_FOREIGN_TABLE &&
+ relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
+ ereport(ERROR,
+ (errcode(ERRCODE_WRONG_OBJECT_TYPE),
+ errmsg("cannot set comment on relation \"%s\"",
+ RelationGetRelationName(relation)),
+ errdetail_relkind_not_supported(relation->rd_rel->relkind)));
+ break;
+ default:
+ break;
+ }
+
+ /*
+ * Databases, tablespaces, and roles are cluster-wide objects, so any
+ * comments on those objects are recorded in the shared pg_shdescription
+ * catalog. Comments on all other objects are recorded in pg_description.
+ */
+ if (stmt->objtype == OBJECT_DATABASE || stmt->objtype == OBJECT_TABLESPACE
+ || stmt->objtype == OBJECT_ROLE)
+ CreateSharedComments(address.objectId, address.classId, stmt->comment);
+ else
+ CreateComments(address.objectId, address.classId, address.objectSubId,
+ stmt->comment);
+
+ /*
+ * If get_object_address() opened the relation for us, we close it to keep
+ * the reference count correct - but we retain any locks acquired by
+ * get_object_address() until commit time, to guard against concurrent
+ * activity.
+ */
+ if (relation != NULL)
+ relation_close(relation, NoLock);
+
+ return address;
+}
+
+/*
+ * CreateComments --
+ *
+ * Create a comment for the specified object descriptor. Inserts a new
+ * pg_description tuple, or replaces an existing one with the same key.
+ *
+ * If the comment given is null or an empty string, instead delete any
+ * existing comment for the specified key.
+ */
+void
+CreateComments(Oid oid, Oid classoid, int32 subid, const char *comment)
+{
+ Relation description;
+ ScanKeyData skey[3];
+ SysScanDesc sd;
+ HeapTuple oldtuple;
+ HeapTuple newtuple = NULL;
+ Datum values[Natts_pg_description];
+ bool nulls[Natts_pg_description];
+ bool replaces[Natts_pg_description];
+ int i;
+
+ /* Reduce empty-string to NULL case */
+ if (comment != NULL && strlen(comment) == 0)
+ comment = NULL;
+
+ /* Prepare to form or update a tuple, if necessary */
+ if (comment != NULL)
+ {
+ for (i = 0; i < Natts_pg_description; i++)
+ {
+ nulls[i] = false;
+ replaces[i] = true;
+ }
+ values[Anum_pg_description_objoid - 1] = ObjectIdGetDatum(oid);
+ values[Anum_pg_description_classoid - 1] = ObjectIdGetDatum(classoid);
+ values[Anum_pg_description_objsubid - 1] = Int32GetDatum(subid);
+ values[Anum_pg_description_description - 1] = CStringGetTextDatum(comment);
+ }
+
+ /* Use the index to search for a matching old tuple */
+
+ ScanKeyInit(&skey[0],
+ Anum_pg_description_objoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(oid));
+ ScanKeyInit(&skey[1],
+ Anum_pg_description_classoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(classoid));
+ ScanKeyInit(&skey[2],
+ Anum_pg_description_objsubid,
+ BTEqualStrategyNumber, F_INT4EQ,
+ Int32GetDatum(subid));
+
+ description = table_open(DescriptionRelationId, RowExclusiveLock);
+
+ sd = systable_beginscan(description, DescriptionObjIndexId, true,
+ NULL, 3, skey);
+
+ while ((oldtuple = systable_getnext(sd)) != NULL)
+ {
+ /* Found the old tuple, so delete or update it */
+
+ if (comment == NULL)
+ CatalogTupleDelete(description, &oldtuple->t_self);
+ else
+ {
+ newtuple = heap_modify_tuple(oldtuple, RelationGetDescr(description), values,
+ nulls, replaces);
+ CatalogTupleUpdate(description, &oldtuple->t_self, newtuple);
+ }
+
+ break; /* Assume there can be only one match */
+ }
+
+ systable_endscan(sd);
+
+ /* If we didn't find an old tuple, insert a new one */
+
+ if (newtuple == NULL && comment != NULL)
+ {
+ newtuple = heap_form_tuple(RelationGetDescr(description),
+ values, nulls);
+ CatalogTupleInsert(description, newtuple);
+ }
+
+ if (newtuple != NULL)
+ heap_freetuple(newtuple);
+
+ /* Done */
+
+ table_close(description, NoLock);
+}
+
+/*
+ * CreateSharedComments --
+ *
+ * Create a comment for the specified shared object descriptor. Inserts a
+ * new pg_shdescription tuple, or replaces an existing one with the same key.
+ *
+ * If the comment given is null or an empty string, instead delete any
+ * existing comment for the specified key.
+ */
+void
+CreateSharedComments(Oid oid, Oid classoid, const char *comment)
+{
+ Relation shdescription;
+ ScanKeyData skey[2];
+ SysScanDesc sd;
+ HeapTuple oldtuple;
+ HeapTuple newtuple = NULL;
+ Datum values[Natts_pg_shdescription];
+ bool nulls[Natts_pg_shdescription];
+ bool replaces[Natts_pg_shdescription];
+ int i;
+
+ /* Reduce empty-string to NULL case */
+ if (comment != NULL && strlen(comment) == 0)
+ comment = NULL;
+
+ /* Prepare to form or update a tuple, if necessary */
+ if (comment != NULL)
+ {
+ for (i = 0; i < Natts_pg_shdescription; i++)
+ {
+ nulls[i] = false;
+ replaces[i] = true;
+ }
+ values[Anum_pg_shdescription_objoid - 1] = ObjectIdGetDatum(oid);
+ values[Anum_pg_shdescription_classoid - 1] = ObjectIdGetDatum(classoid);
+ values[Anum_pg_shdescription_description - 1] = CStringGetTextDatum(comment);
+ }
+
+ /* Use the index to search for a matching old tuple */
+
+ ScanKeyInit(&skey[0],
+ Anum_pg_shdescription_objoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(oid));
+ ScanKeyInit(&skey[1],
+ Anum_pg_shdescription_classoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(classoid));
+
+ shdescription = table_open(SharedDescriptionRelationId, RowExclusiveLock);
+
+ sd = systable_beginscan(shdescription, SharedDescriptionObjIndexId, true,
+ NULL, 2, skey);
+
+ while ((oldtuple = systable_getnext(sd)) != NULL)
+ {
+ /* Found the old tuple, so delete or update it */
+
+ if (comment == NULL)
+ CatalogTupleDelete(shdescription, &oldtuple->t_self);
+ else
+ {
+ newtuple = heap_modify_tuple(oldtuple, RelationGetDescr(shdescription),
+ values, nulls, replaces);
+ CatalogTupleUpdate(shdescription, &oldtuple->t_self, newtuple);
+ }
+
+ break; /* Assume there can be only one match */
+ }
+
+ systable_endscan(sd);
+
+ /* If we didn't find an old tuple, insert a new one */
+
+ if (newtuple == NULL && comment != NULL)
+ {
+ newtuple = heap_form_tuple(RelationGetDescr(shdescription),
+ values, nulls);
+ CatalogTupleInsert(shdescription, newtuple);
+ }
+
+ if (newtuple != NULL)
+ heap_freetuple(newtuple);
+
+ /* Done */
+
+ table_close(shdescription, NoLock);
+}
+
+/*
+ * DeleteComments -- remove comments for an object
+ *
+ * If subid is nonzero then only comments matching it will be removed.
+ * If subid is zero, all comments matching the oid/classoid will be removed
+ * (this corresponds to deleting a whole object).
+ */
+void
+DeleteComments(Oid oid, Oid classoid, int32 subid)
+{
+ Relation description;
+ ScanKeyData skey[3];
+ int nkeys;
+ SysScanDesc sd;
+ HeapTuple oldtuple;
+
+ /* Use the index to search for all matching old tuples */
+
+ ScanKeyInit(&skey[0],
+ Anum_pg_description_objoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(oid));
+ ScanKeyInit(&skey[1],
+ Anum_pg_description_classoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(classoid));
+
+ if (subid != 0)
+ {
+ ScanKeyInit(&skey[2],
+ Anum_pg_description_objsubid,
+ BTEqualStrategyNumber, F_INT4EQ,
+ Int32GetDatum(subid));
+ nkeys = 3;
+ }
+ else
+ nkeys = 2;
+
+ description = table_open(DescriptionRelationId, RowExclusiveLock);
+
+ sd = systable_beginscan(description, DescriptionObjIndexId, true,
+ NULL, nkeys, skey);
+
+ while ((oldtuple = systable_getnext(sd)) != NULL)
+ CatalogTupleDelete(description, &oldtuple->t_self);
+
+ /* Done */
+
+ systable_endscan(sd);
+ table_close(description, RowExclusiveLock);
+}
+
+/*
+ * DeleteSharedComments -- remove comments for a shared object
+ */
+void
+DeleteSharedComments(Oid oid, Oid classoid)
+{
+ Relation shdescription;
+ ScanKeyData skey[2];
+ SysScanDesc sd;
+ HeapTuple oldtuple;
+
+ /* Use the index to search for all matching old tuples */
+
+ ScanKeyInit(&skey[0],
+ Anum_pg_shdescription_objoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(oid));
+ ScanKeyInit(&skey[1],
+ Anum_pg_shdescription_classoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(classoid));
+
+ shdescription = table_open(SharedDescriptionRelationId, RowExclusiveLock);
+
+ sd = systable_beginscan(shdescription, SharedDescriptionObjIndexId, true,
+ NULL, 2, skey);
+
+ while ((oldtuple = systable_getnext(sd)) != NULL)
+ CatalogTupleDelete(shdescription, &oldtuple->t_self);
+
+ /* Done */
+
+ systable_endscan(sd);
+ table_close(shdescription, RowExclusiveLock);
+}
+
+/*
+ * GetComment -- get the comment for an object, or null if not found.
+ */
+char *
+GetComment(Oid oid, Oid classoid, int32 subid)
+{
+ Relation description;
+ ScanKeyData skey[3];
+ SysScanDesc sd;
+ TupleDesc tupdesc;
+ HeapTuple tuple;
+ char *comment;
+
+ /* Use the index to search for a matching old tuple */
+
+ ScanKeyInit(&skey[0],
+ Anum_pg_description_objoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(oid));
+ ScanKeyInit(&skey[1],
+ Anum_pg_description_classoid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(classoid));
+ ScanKeyInit(&skey[2],
+ Anum_pg_description_objsubid,
+ BTEqualStrategyNumber, F_INT4EQ,
+ Int32GetDatum(subid));
+
+ description = table_open(DescriptionRelationId, AccessShareLock);
+ tupdesc = RelationGetDescr(description);
+
+ sd = systable_beginscan(description, DescriptionObjIndexId, true,
+ NULL, 3, skey);
+
+ comment = NULL;
+ while ((tuple = systable_getnext(sd)) != NULL)
+ {
+ Datum value;
+ bool isnull;
+
+ /* Found the tuple, get description field */
+ value = heap_getattr(tuple, Anum_pg_description_description, tupdesc, &isnull);
+ if (!isnull)
+ comment = TextDatumGetCString(value);
+ break; /* Assume there can be only one match */
+ }
+
+ systable_endscan(sd);
+
+ /* Done */
+ table_close(description, AccessShareLock);
+
+ return comment;
+}
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