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Clarify handling of NULL values in PK columns in sqlite3session.h. Add tests and fixes for the same.

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FossilOrigin-Name: aed4273054cbd150c86b36ea951d17c981633ba0
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dan
2011-03-21 11:55:06 +00:00
parent 4e895da185
commit 27453faef8
5 changed files with 235 additions and 214 deletions
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17
ext/session/sqlite3session.h
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@ -106,6 +106,9 @@ int sqlite3session_enable(sqlite3_session *pSession, int bEnable);
** is it an error if the named table does not have a PRIMARY KEY. However,
** no changes will be recorded in either of these scenarios.
**
** Changes are not recorded for individual rows that have NULL values stored
** in one or more of their PRIMARY KEY columns.
**
** SQLITE_OK is returned if the table is successfully attached to the session
** object. Or, if an error occurs, an SQLite error code (e.g. SQLITE_NOMEM)
** is returned.
@ -135,6 +138,16 @@ int sqlite3session_attach(
** 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()]
@ -153,6 +166,10 @@ int sqlite3session_attach(
** 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 contains 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