Update design doc with value alignment design

This feature is not implemented, and there is no clear path to implementing it (see #360). However, if it becomes possible to implement it in the future, this design should be backward compatible
cberner · Feb 11, 2023 · e50cc24 · e50cc24
1 parent f5eba2d
commit e50cc24
Showing 1 changed file with 9 additions and 3 deletions.
diff --git a/docs/design.md b/docs/design.md
@@ -238,7 +238,7 @@ Allocated pages may be of two types: b-tree branch pages, or b-tree leaf pages.
 --------------------------------------------------------------------------------------------------
 | child page number (repeated num_keys + 1 times)                                                |
 --------------------------------------------------------------------------------------------------
-| (optional) key end (repeated num_keys times) | ... more key ends                               |
+| (optional) key end (repeated num_keys times) | alignment padding                               |
 ==================================================================================================
 | Key data                                                                                       |
 ==================================================================================================
@@ -253,6 +253,8 @@ Allocated pages may be of two types: b-tree branch pages, or b-tree leaf pages.
 
 `key_end` is an array of ending offsets for the keys. It is optional, MUST NOT be stored for fixed width key types
 
+`alignment padding` optional padding so that the key data begins at a multiple of the key type's required alignment
+
 ### Leaf page:
 * 1 byte: type
 * 1 byte: reserved (padding to 16bits aligned)
@@ -270,9 +272,9 @@ Allocated pages may be of two types: b-tree branch pages, or b-tree leaf pages.
 ==================================================================================================
 | type     | padding   | number of entries      | (optional) key end (repeated entries times)    |
 --------------------------------------------------------------------------------------------------
-| (optional) value end (repeated entries times) | .. more key/value ends                         |
+| (optional) value end (repeated entries times) | (optional) key alignment padding               |
 ==================================================================================================
-| Key data                                                                                       |
+| Key data                                      | (optional) value alignment padding             |
 ==================================================================================================
 | Value data                                                                                     |
 ==================================================================================================
@@ -286,6 +288,10 @@ Allocated pages may be of two types: b-tree branch pages, or b-tree leaf pages.
 
 `value_end` is an array of ending offsets for the values. It is optional, MUST NOT be stored for fixed width value types
 
+`key alignment padding` optional padding so that the key data begins at a multiple of the key type's required alignment
+
+`value alignment padding` optional padding so that the value data begins at a multiple of the value type's required alignment
+
 # Commit strategies
 
 All redb transactions are atomic, and use one of the following commit strategies.