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Fix for ticket #42: Added comments to structs Trigger, TriggerStep and TriggerStack. (CVS 569)

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FossilOrigin-Name: 9ec8a2b139ce38312284d7b4eb61221b1e1e3052
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danielk1977
2002-05-16 00:13:12 +00:00
parent b6b2de0c35
commit d99bc930f7
3 changed files with 136 additions and 35 deletions
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155
src/sqliteInt.h
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@ -11,7 +11,7 @@
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.109 2002/05/15 12:45:43 drh Exp $
** @(#) $Id: sqliteInt.h,v 1.110 2002/05/16 00:13:12 danielk1977 Exp $
*/
#include "sqlite.h"
#include "hash.h"
@ -561,46 +561,147 @@ struct Parse {
TriggerStack *trigStack;
};
struct TriggerStack {
Trigger *pTrigger;
Table *pTab; /* Table that triggers are currently being coded as */
int newIdx; /* Index of "new" temp table */
int oldIdx; /* Index of "old" temp table */
int orconf; /* Current orconf policy */
TriggerStack *pNext;
};
struct TriggerStep {
int op; /* One of TK_DELETE, TK_UPDATE, TK_INSERT, TK_SELECT */
int orconf;
Select *pSelect; /* Valid for SELECT and sometimes
INSERT steps (when pExprList == 0) */
Token target; /* Valid for DELETE, UPDATE, INSERT steps */
Expr *pWhere; /* Valid for DELETE, UPDATE steps */
ExprList *pExprList; /* Valid for UPDATE statements and sometimes
INSERT steps (when pSelect == 0) */
IdList *pIdList; /* Valid for INSERT statements only */
TriggerStep * pNext; /* Next in the link-list */
};
/*
* Each trigger present in the database schema is stored as an instance of
* struct Trigger.
*
* Pointers to instances of struct Trigger are stored in two ways.
* 1. In the "trigHash" hash table (part of the sqlite* that represents the
* database). This allows Trigger structures to be retrieved by name.
* 2. All triggers associated with a single table form a linked list, using the
* pNext member of struct Trigger. A pointer to the first element of the linked
* list is stored as the "pTrigger" member of the associated struct Table.
*
* The "strings" member of struct Trigger contains a pointer to the memory
* referenced by the various Token structures referenced indirectly by the
* "pWhen", "pColumns" and "step_list" members. (ie. the memory allocated for
* use in conjunction with the sqliteExprMoveStrings() etc. interface).
*
* The "step_list" member points to the first element of a linked list containing
* the SQL statements specified as the trigger program.
*
* When a trigger is initially created, the "isCommit" member is set to FALSE.
* When a transaction is rolled back, any Trigger structures with "isCommit" set
* to FALSE are deleted by the logic in sqliteRollbackInternalChanges(). When
* a transaction is commited, the "isCommit" member is set to TRUE for any
* Trigger structures for which it is FALSE.
*
* When a trigger is dropped, using the sqliteDropTrigger() interfaced, it is
* removed from the trigHash hash table and added to the trigDrop hash table. If
* the transaction is rolled back, the trigger is re-added into the trigHash
* hash table (and hence the database schema). If the transaction is commited,
* then the Trigger structure is deleted permanently.
*/
struct Trigger {
char *name; /* The name of the trigger */
char *table; /* The table or view to which the trigger applies */
int op; /* One of TK_DELETE, TK_UPDATE, TK_INSERT */
int tr_tm; /* One of TK_BEFORE, TK_AFTER, TK_INSTEAD */
int tr_tm; /* One of TK_BEFORE, TK_AFTER */
Expr *pWhen; /* The WHEN clause of the expresion (may be NULL) */
IdList *pColumns; /* If this is an UPDATE OF <column-list> trigger,
the column names are stored in this list */
the <column-list> is stored here */
int foreach; /* One of TK_ROW or TK_STATEMENT */
TriggerStep *step_list; /* Link list of trigger program steps */
char *strings; /* pointer to allocation of Token strings */
Trigger *pNext; /* Next trigger associated with the table */
int isCommit;
int isCommit; /* Set to TRUE once the trigger has been committed */
};
extern int always_code_trigger_setup;
/*
* An instance of struct TriggerStep is used to store a single SQL statement
* that is a part of a trigger-program.
*
* Instances of struct TriggerStep are stored in a singly linked list (linked
* using the "pNext" member) referenced by the "step_list" member of the
* associated struct Trigger instance. The first element of the linked list is
* the first step of the trigger-program.
*
* The "op" member indicates whether this is a "DELETE", "INSERT", "UPDATE" or
* "SELECT" statement. The meanings of the other members is determined by the
* value of "op" as follows:
*
* (op == TK_INSERT)
* orconf -> stores the ON CONFLICT algorithm
* pSelect -> If this is an INSERT INTO ... SELECT ... statement, then
* this stores a pointer to the SELECT statement. Otherwise NULL.
* target -> A token holding the name of the table to insert into.
* pExprList -> If this is an INSERT INTO ... VALUES ... statement, then
* this stores values to be inserted. Otherwise NULL.
* pIdList -> If this is an INSERT INTO ... (<column-names>) VALUES ...
* statement, then this stores the column-names to be inserted into.
*
* (op == TK_DELETE)
* target -> A token holding the name of the table to delete from.
* pWhere -> The WHERE clause of the DELETE statement if one is specified.
* Otherwise NULL.
*
* (op == TK_UPDATE)
* target -> A token holding the name of the table to update rows of.
* pWhere -> The WHERE clause of the UPDATE statement if one is specified.
* Otherwise NULL.
* pExprList -> A list of the columns to update and the expressions to update
* them to. See sqliteUpdate() documentation of "pChanges" argument.
*
*/
struct TriggerStep {
int op; /* One of TK_DELETE, TK_UPDATE, TK_INSERT, TK_SELECT */
int orconf; /* OE_Rollback etc. */
Select *pSelect; /* Valid for SELECT and sometimes
INSERT steps (when pExprList == 0) */
Token target; /* Valid for DELETE, UPDATE, INSERT steps */
Expr *pWhere; /* Valid for DELETE, UPDATE steps */
ExprList *pExprList; /* Valid for UPDATE statements and sometimes
INSERT steps (when pSelect == 0) */
IdList *pIdList; /* Valid for INSERT statements only */
TriggerStep * pNext; /* Next in the link-list */
};
/*
* An instance of struct TriggerStack stores information required during code
* generation of a single trigger program. While the trigger program is being
* coded, its associated TriggerStack instance is pointed to by the
* "pTriggerStack" member of the Parse structure.
*
* The pTab member points to the table that triggers are being coded on. The
* newIdx member contains the index of the vdbe cursor that points at the temp
* table that stores the new.* references. If new.* references are not valid
* for the trigger being coded (for example an ON DELETE trigger), then newIdx
* is set to -1. The oldIdx member is analogous to newIdx, for old.* references.
*
* The ON CONFLICT policy to be used for the trigger program steps is stored
* as the orconf member. If this is OE_Default, then the ON CONFLICT clause
* specified for individual triggers steps is used.
*
* struct TriggerStack has a "pNext" member, to allow linked lists to be
* constructed. When coding nested triggers (triggers fired by other triggers)
* each nested trigger stores its parent trigger's TriggerStack as the "pNext"
* pointer. Once the nested trigger has been coded, the pNext value is restored
* to the pTriggerStack member of the Parse stucture and coding of the parent
* trigger continues.
*
* Before a nested trigger is coded, the linked list pointed to by the
* pTriggerStack is scanned to ensure that the trigger is not about to be coded
* recursively. If this condition is detected, the nested trigger is not coded.
*/
struct TriggerStack {
Table *pTab; /* Table that triggers are currently being coded on */
int newIdx; /* Index of vdbe cursor to "new" temp table */
int oldIdx; /* Index of vdbe cursor to "old" temp table */
int orconf; /* Current orconf policy */
Trigger *pTrigger;
TriggerStack *pNext;
};
/*
* This global flag is set for performance testing of triggers. When it is set
* SQLite will perform the overhead of building new and old trigger references
* even when no triggers exist
*/
extern int always_code_trigger_setup;
/*
** Internal function prototypes