(cloudberry) 01/01: Lock table in DROP STATISTICS

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reshke pushed a commit to branch bp_9dd50e92ed239bc4643c1df7e9e0bcc03b05bfef
in repository https://gitbox.apache.org/repos/asf/cloudberry.git

commit 13511eaeeee1ba6b44714eeef0fcdd90a6b28303
Author: Tomas Vondra <to...@postgresql.org>
AuthorDate: Sun Nov 19 21:03:29 2023 +0100

    Lock table in DROP STATISTICS
    
    The DROP STATISTICS code failed to properly lock the table, leading to
    
      ERROR:  tuple concurrently deleted
    
    when executed concurrently with ANALYZE.
    
    Fixed by modifying RemoveStatisticsById() to acquire the same lock as
    ANALYZE. This function is called only by DROP STATISTICS, as ANALYZE
    calls RemoveStatisticsDataById() directly.
    
    Reported by Justin Pryzby, fix by me. Backpatch through 12. The code was
    like this since it was introduced in 10, but older releases are EOL.
    
    Reported-by: Justin Pryzby
    Reviewed-by: Tom Lane
    Backpatch-through: 12
    
    Discussion: https://postgr.es/m/ZUuk-8CfbYeq6g_u@pryzbyj2023
---
 src/backend/commands/statscmds.c | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/src/backend/commands/statscmds.c b/src/backend/commands/statscmds.c
index 4cf7ae7b2e3..a44b2694522 100644
--- a/src/backend/commands/statscmds.c
+++ b/src/backend/commands/statscmds.c
@@ -741,20 +741,14 @@ AlterStatistics(AlterStatsStmt *stmt)
 }
 
 /*
- * Guts of statistics object deletion.
- */
-void
-RemoveStatisticsById(Oid statsOid)
+ * Delete entry in pg_statistic_ext_data catalog.
+*/
+static void
+RemoveStatisticsDataById(Oid statsOid)
 {
 	Relation	relation;
 	HeapTuple	tup;
-	Form_pg_statistic_ext statext;
-	Oid			relid;
 
-	/*
-	 * First delete the pg_statistic_ext_data tuple holding the actual
-	 * statistical data.
-	 */
 	relation = table_open(StatisticExtDataRelationId, RowExclusiveLock);
 
 	tup = SearchSysCache1(STATEXTDATASTXOID, ObjectIdGetDatum(statsOid));
@@ -767,6 +761,19 @@ RemoveStatisticsById(Oid statsOid)
 	ReleaseSysCache(tup);
 
 	table_close(relation, RowExclusiveLock);
+}
+
+/*
+ * Guts of statistics object deletion.
+ */
+void
+RemoveStatisticsById(Oid statsOid)
+{
+	Relation	relation;
+	Relation	rel;
+	HeapTuple	tup;
+	Form_pg_statistic_ext statext;
+	Oid			relid;
 
 	/*
 	 * Delete the pg_statistic_ext tuple.  Also send out a cache inval on the
@@ -782,12 +789,24 @@ RemoveStatisticsById(Oid statsOid)
 	statext = (Form_pg_statistic_ext) GETSTRUCT(tup);
 	relid = statext->stxrelid;
 
+	/*
+	 * Delete the pg_statistic_ext_data tuple holding the actual statistical
+	 * data. We lock the user table first, to prevent other processes (e.g.
+	 * DROP STATISTICS) from removing the row concurrently.
+	 */
+	rel = table_open(relid, ShareUpdateExclusiveLock);
+
+	RemoveStatisticsDataById(statsOid);
+
 	CacheInvalidateRelcacheByRelid(relid);
 
 	CatalogTupleDelete(relation, &tup->t_self);
 
 	ReleaseSysCache(tup);
 
+	/* Keep lock until the end of the transaction. */
+	table_close(rel, NoLock);
+
 	table_close(relation, RowExclusiveLock);
 }
 


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