From 63847496f14c813a5d80efd5b7de0f1294ffe1e3 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 13 Apr 2024 16:07:11 +0200 Subject: Adding upstream version 3.45.1. Signed-off-by: Daniel Baumann --- www/session/sqlite3session_changeset.html | 228 ++++++++++++++++++++++++++++++ 1 file changed, 228 insertions(+) create mode 100644 www/session/sqlite3session_changeset.html (limited to 'www/session/sqlite3session_changeset.html') diff --git a/www/session/sqlite3session_changeset.html b/www/session/sqlite3session_changeset.html new file mode 100644 index 0000000..df9a39c --- /dev/null +++ b/www/session/sqlite3session_changeset.html @@ -0,0 +1,228 @@ + + + + + +Generate A Changeset From A Session Object + + + +
+ + + +
+
+Small. Fast. Reliable.
Choose any three. +
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Session Module C Interface

Generate A Changeset From A Session Object

int sqlite3session_changeset(
+  sqlite3_session *pSession,      /* Session object */
+  int *pnChangeset,               /* OUT: Size of buffer at *ppChangeset */
+  void **ppChangeset              /* OUT: Buffer containing changeset */
+);
+

+Obtain a changeset containing changes to the tables attached to the +session object passed as the first argument. If successful, +set *ppChangeset to point to a buffer containing the changeset +and *pnChangeset to the size of the changeset in bytes before returning +SQLITE_OK. If an error occurs, set both *ppChangeset and *pnChangeset to +zero and return an SQLite error code.

+ +

A changeset consists of zero or more INSERT, UPDATE and/or DELETE changes, +each representing a change to a single row of an attached table. An INSERT +change contains the values of each field of a new database row. A DELETE +contains the original values of each field of a deleted database row. An +UPDATE change contains the original values of each field of an updated +database row along with the updated values for each updated non-primary-key +column. It is not possible for an UPDATE change to represent a change that +modifies the values of primary key columns. If such a change is made, it +is represented in a changeset as a DELETE followed by an INSERT.

+ +

Changes are not recorded for rows that have NULL values stored in one or +more of their PRIMARY KEY columns. If such a row is inserted or deleted, +no corresponding change is present in the changesets returned by this +function. If an existing row with one or more NULL values stored in +PRIMARY KEY columns is updated so that all PRIMARY KEY columns are non-NULL, +only an INSERT is appears in the changeset. Similarly, if an existing row +with non-NULL PRIMARY KEY values is updated so that one or more of its +PRIMARY KEY columns are set to NULL, the resulting changeset contains a +DELETE change only.

+ +

The contents of a changeset may be traversed using an iterator created +using the sqlite3changeset_start() API. A changeset may be applied to +a database with a compatible schema using the sqlite3changeset_apply() +API.

+ +

Within a changeset generated by this function, all changes related to a +single table are grouped together. In other words, when iterating through +a changeset or when applying a changeset to a database, all changes related +to a single table are processed before moving on to the next table. Tables +are sorted in the same order in which they were attached (or auto-attached) +to the sqlite3_session object. The order in which the changes related to +a single table are stored is undefined.

+ +

Following a successful call to this function, it is the responsibility of +the caller to eventually free the buffer that *ppChangeset points to using +sqlite3_free().

+ +

Changeset Generation

+ +

Once a table has been attached to a session object, the session object +records the primary key values of all new rows inserted into the table. +It also records the original primary key and other column values of any +deleted or updated rows. For each unique primary key value, data is only +recorded once - the first time a row with said primary key is inserted, +updated or deleted in the lifetime of the session.

+ +

There is one exception to the previous paragraph: when a row is inserted, +updated or deleted, if one or more of its primary key columns contain a +NULL value, no record of the change is made.

+ +

The session object therefore accumulates two types of records - those +that consist of primary key values only (created when the user inserts +a new record) and those that consist of the primary key values and the +original values of other table columns (created when the users deletes +or updates a record).

+ +

When this function is called, the requested changeset is created using +both the accumulated records and the current contents of the database +file. Specifically:

+ +

+ +

This means, amongst other things, that if a row is inserted and then later +deleted while a session object is active, neither the insert nor the delete +will be present in the changeset. Or if a row is deleted and then later a +row with the same primary key values inserted while a session object is +active, the resulting changeset will contain an UPDATE change instead of +a DELETE and an INSERT.

+ +

When a session object is disabled (see the sqlite3session_enable() API), +it does not accumulate records when rows are inserted, updated or deleted. +This may appear to have some counter-intuitive effects if a single row +is written to more than once during a session. For example, if a row +is inserted while a session object is enabled, then later deleted while +the same session object is disabled, no INSERT record will appear in the +changeset, even though the delete took place while the session was disabled. +Or, if one field of a row is updated while a session is disabled, and +another field of the same row is updated while the session is enabled, the +resulting changeset will contain an UPDATE change that updates both fields. +

See also lists of + Objects, + Constants, and + Functions.

+ -- cgit v1.2.3