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commit    2959213bf33cf7d2d1fc0b46c67d36254ffe043f
Author:   Robert Haas <rhaas@postgresql.org>
Date:     Fri Oct 20 13:40:17 2017 +0000

    pg_stat_statements: Add a comment about the dangers of padding bytes.
    
    Inspired by a patch from Julien Rouhaud, but I reworded it.
    
    Discussion: http://postgr.es/m/CAOBaU_a8AH8=ypfqgHnDYu06ts+jWTUgh=VgCxA3yNV-K10j9w@mail.gmail.com


 contrib/pg_stat_statements/pg_stat_statements.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index b04b4d6ce11..3de8333be2b 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -125,6 +125,11 @@ typedef enum pgssVersion
 /*
  * Hashtable key that defines the identity of a hashtable entry.  We separate
  * queries by user and by database even if they are otherwise identical.
+ *
+ * Right now, this structure contains no padding.  If you add any, make sure
+ * to teach pgss_store() to zero the padding bytes.  Otherwise, things will
+ * break, because pgss_hash is created using HASH_BLOBS, and thus tag_hash
+ * is used to hash this.
  */
 typedef struct pgssHashKey
 {


[parent: e250c8c8408a]