Improved comments on foreign key logic.
FossilOrigin-Name: 1315d9109c7105f4a62bb2d43ca6948d41245129
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 8890cbe..43a82b7 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1451,26 +1451,35 @@
** );
**
** For foreign key "fk1", the from-table is "ex1" and the to-table is "ex2".
+** Equivalent names:
+**
+** from-table == child-table
+** to-table == parent-table
**
** Each REFERENCES clause generates an instance of the following structure
** which is attached to the from-table. The to-table need not exist when
** the from-table is created. The existence of the to-table is not checked.
+**
+** The list of all parents for child Table X is held at X.pFKey.
+**
+** A list of all children for a table named Z (which might not even exist)
+** is held in Schema.fkeyHash with a hash key of Z.
*/
struct FKey {
Table *pFrom; /* Table containing the REFERENCES clause (aka: Child) */
- FKey *pNextFrom; /* Next foreign key in pFrom */
+ FKey *pNextFrom; /* Next FKey with the same in pFrom. Next parent of pFrom */
char *zTo; /* Name of table that the key points to (aka: Parent) */
- FKey *pNextTo; /* Next foreign key on table named zTo */
- FKey *pPrevTo; /* Previous foreign key on table named zTo */
+ FKey *pNextTo; /* Next with the same zTo. Next child of zTo. */
+ FKey *pPrevTo; /* Previous with the same zTo */
int nCol; /* Number of columns in this key */
/* EV: R-30323-21917 */
- u8 isDeferred; /* True if constraint checking is deferred till COMMIT */
- u8 aAction[2]; /* ON DELETE and ON UPDATE actions, respectively */
- Trigger *apTrigger[2]; /* Triggers for aAction[] actions */
- struct sColMap { /* Mapping of columns in pFrom to columns in zTo */
- int iFrom; /* Index of column in pFrom */
- char *zCol; /* Name of column in zTo. If 0 use PRIMARY KEY */
- } aCol[1]; /* One entry for each of nCol column s */
+ u8 isDeferred; /* True if constraint checking is deferred till COMMIT */
+ u8 aAction[2]; /* ON DELETE and ON UPDATE actions, respectively */
+ Trigger *apTrigger[2];/* Triggers for aAction[] actions */
+ struct sColMap { /* Mapping of columns in pFrom to columns in zTo */
+ int iFrom; /* Index of column in pFrom */
+ char *zCol; /* Name of column in zTo. If NULL use PRIMARY KEY */
+ } aCol[1]; /* One entry for each of nCol columns */
};
/*