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Implement SQL_ATTR_CONNECTION_DEAD for ODBC #9353

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Implement SQL_ATTR_CONNECTION_DEAD for ODBC #9353

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4472a93
Procedural ODBC: SQL_ATTR_CONNECTION_DEAD
NattyNarwhal Aug 16, 2022
41595cb
PDO ODBC: SQL_ATTR_CONNECTION_DEAD
NattyNarwhal Aug 16, 2022
7d527f5
Only use old heuristic on failure of new check
NattyNarwhal Aug 22, 2022
8019082
Adjust comments to clarify that CD_FALSE -> fall back
NattyNarwhal Aug 23, 2022
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10 changes: 10 additions & 0 deletions ext/odbc/php_odbc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2246,7 +2246,17 @@ void odbc_do_connect(INTERNAL_FUNCTION_PARAMETERS, int persistent)
RETCODE ret;
UCHAR d_name[32];
SQLSMALLINT len;
SQLUINTEGER dead = SQL_CD_FALSE;

ret = SQLGetConnectAttr(db_conn->hdbc,
SQL_ATTR_CONNECTION_DEAD,
&dead, 0, NULL);
if (dead == SQL_CD_TRUE) {
/* Bail early here, since we know it's gone */
zend_hash_str_del(&EG(persistent_list), hashed_details, hashed_len);
goto try_and_get_another_connection;
}
/* If the driver doesn't support it, fall back to old heuristic */
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Hmm, can't we assume that the driver supports SQL_ATTR_CONNECTION_DEAD if ret == SQL_SUCCESS? I mean, can't we skip the fallback (SQL_DATA_SOURCE_READ_ONLY) regardless of the value of dead?

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Unfortunately, the Db2i driver at least had a case where it would return SQL_CD_FALSE, but the heuristic would detect a failed connection. However, that case (specifically, admin killing the database server process) is pretty weird and uncommon (though people bug me enough about it I have to mention it). You're probably right; it'd be better to just trust SQL_ATTR_CONNECTION_DEAD, and get driver authors to implement more accurate results if they're going to use it.

ret = SQLGetInfo(db_conn->hdbc,
SQL_DATA_SOURCE_READ_ONLY,
d_name, sizeof(d_name), &len);
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11 changes: 9 additions & 2 deletions ext/pdo_odbc/odbc_driver.c
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Expand Up @@ -396,11 +396,18 @@ static zend_result odbc_handle_check_liveness(pdo_dbh_t *dbh)
RETCODE ret;
UCHAR d_name[32];
SQLSMALLINT len;
SQLUINTEGER dead = SQL_CD_FALSE;
pdo_odbc_db_handle *H = (pdo_odbc_db_handle *)dbh->driver_data;

ret = SQLGetConnectAttr(H->dbc, SQL_ATTR_CONNECTION_DEAD, &dead, 0, NULL);
if (dead == SQL_CD_TRUE) {
/* Bail early here, since we know it's gone */
return FAILURE;
}
/*
* SQL_ATTR_CONNECTION_DEAD is tempting, but only in ODBC 3.5,
* and not all drivers implement it properly
* If the driver doesn't support SQL_ATTR_CONNECTION_DEAD, fall back
* to using SQL_DATA_SOURCE_READ_ONLY, which isn't semantically
* correct, but works with many drivers.
*/
ret = SQLGetInfo(H->dbc, SQL_DATA_SOURCE_READ_ONLY, d_name,
sizeof(d_name), &len);
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