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MDL-17491 oracle native driver: normalise empty behaviour (dirty hack) to

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work with all CHAR/CLOB columns and implemente oracle transactions support.
This commit is contained in:
stronk7 2009-09-22 16:44:27 +00:00
parent cf874b2949
commit 9a61e6ba1f
1 changed files with 75 additions and 68 deletions
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143
lib/dml/oci_native_moodle_database.php
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@ -546,7 +546,7 @@ class oci_native_moodle_database extends moodle_database {
* @return mixed the normalised value
*/
private function normalise_value($column, $value) {
if (is_bool($value)) { /// Always, convert boolean to int
if (is_bool($value)) { // Always, convert boolean to int
$value = (int)$value;
} else if ($column->meta_type == 'B') { // CLOB detected, we return 'blob' array instead of raw value to allow
@ -568,14 +568,13 @@ class oci_native_moodle_database extends moodle_database {
}
/**
* This function will handle all the records before being inserted/updated to DB for Oracle
* This function will handle all the column values before being inserted/updated to DB for Oracle
* installations. This is because the "special feature" of Oracle where the empty string is
* equal to NULL and this presents a problem with all our currently NOT NULL default '' fields.
*
* Once Moodle DB will be free of this sort of false NOT NULLS, this hack could be removed safely
* (and with empties handling in general)
*
* Note that this function is 100% private and should be used, exclusively by DML functions
* in this file. Also, this is considered a DIRTY HACK to be removed when possible. (stronk7)
* in this file. Also, this is considered a DIRTY HACK to be removed when possible.
*
* This function is private and must not be used outside this driver at all
*
@ -585,63 +584,84 @@ class oci_native_moodle_database extends moodle_database {
*/
private function oracle_dirty_hack ($table, $field, $value) {
/// Get metadata
// Get metadata
$columns = $this->get_columns($table);
if (!isset($columns[$field])) {
return $value;
}
$column = $columns[$field];
/// For Oracle DB, empty strings are converted to NULLs in DB
/// and this breaks a lot of NOT NULL columns currenty Moodle. In the future it's
/// planned to move some of them to NULL, if they must accept empty values and this
/// piece of code will become less and less used. But, for now, we need it.
/// What we are going to do is to examine all the data being inserted and if it's
/// an empty string (NULL for Oracle) and the field is defined as NOT NULL, we'll modify
/// such data in the best form possible ("0" for booleans and numbers and " " for the
/// rest of strings. It isn't optimal, but the only way to do so.
/// In the oppsite, when retrieving records from Oracle, we'll decode " " back to
/// empty strings to allow everything to work properly. DIRTY HACK.
// !! This paragraph explains behaviour before Moodle 2.0:
//
// For Oracle DB, empty strings are converted to NULLs in DB
// and this breaks a lot of NOT NULL columns currenty Moodle. In the future it's
// planned to move some of them to NULL, if they must accept empty values and this
// piece of code will become less and less used. But, for now, we need it.
// What we are going to do is to examine all the data being inserted and if it's
// an empty string (NULL for Oracle) and the field is defined as NOT NULL, we'll modify
// such data in the best form possible ("0" for booleans and numbers and " " for the
// rest of strings. It isn't optimal, but the only way to do so.
// In the oppsite, when retrieving records from Oracle, we'll decode " " back to
// empty strings to allow everything to work properly. DIRTY HACK.
/// If the field ins't VARCHAR or CLOB, skip
// !! These paragraphs explain the rationale about the change for Moodle 2.0:
//
// Before Moodle 2.0, we only used to apply this DIRTY HACK to NOT NULL columns, as
// stated above, but it causes one problem in NULL columns where both empty strings
// and real NULLs are stored as NULLs, being impossible to diferentiate them when
// being retrieved from DB.
//
// So, starting with Moodle 2.0, we are going to apply the DIRTY HACK to all the
// CHAR/CLOB columns no matter of their nullability. That way, when retrieving
// NULLABLE fields we'll get proper empties and NULLs diferentiated, so we'll be able
// to rely in NULL/empty/content contents without problems, until now that wasn't
// possible at all.
//
// No breackage with old data is expected as long as at the time of writing this
// (20090922) all the current uses of both sql_empty() and sql_isempty() has been
// revised in 2.0 and all them were being performed against NOT NULL columns,
// where nothing has changed (the DIRTY HACK was already being applied).
//
// !! Conclusions:
//
// From Moodle 2.0 onwards, ALL empty strings in Oracle DBs will be stored as
// 1-whitespace char, ALL NULLs as NULLs and, obviously, content as content. And
// those 1-whitespace chars will be converted back to empty strings by all the
// get_field/record/set() functions transparently and any SQL needing direct handling
// of empties will need to use the sql_empty() and sql_isempty() helper functions.
// MDL-17491.
// If the field ins't VARCHAR or CLOB, skip
if ($column->meta_type != 'C' and $column->meta_type != 'X') {
return $value;
}
/// If the field isn't NOT NULL, skip (it's nullable, so accept empty-null values)
if (!$column->not_null) {
return $value;
}
/// If the value isn't empty, skip
// If the value isn't empty, skip
if (!empty($value)) {
return $value;
}
/// Now, we have one empty value, going to be inserted to one NOT NULL, VARCHAR2 or CLOB field
/// Try to get the best value to be inserted
// Now, we have one empty value, going to be inserted to one VARCHAR2 or CLOB field
// Try to get the best value to be inserted
/// The '0' string doesn't need any transformation, skip
// The '0' string doesn't need any transformation, skip
if ($value === '0') {
return $value;
}
/// Transformations start
// Transformations start
if (gettype($value) == 'boolean') {
return '0'; /// Transform false to '0' that evaluates the same for PHP
return '0'; // Transform false to '0' that evaluates the same for PHP
} else if (gettype($value) == 'integer') {
return '0'; /// Transform 0 to '0' that evaluates the same for PHP
} else if (gettype($value) == 'NULL') {
return '0'; /// Transform NULL to '0' that evaluates the same for PHP
return '0'; // Transform 0 to '0' that evaluates the same for PHP
} else if ($value === '') {
return ' '; /// Transform '' to ' ' that DONT'T EVALUATE THE SAME
/// (we'll transform back again on get_records_XXX functions and others)!!
return ' '; // Transform '' to ' ' that DONT'T EVALUATE THE SAME
// (we'll transform back again on get_records_XXX functions and others)!!
}
/// Fail safe to original value
// Fail safe to original value
return $value;
}
@ -695,7 +715,7 @@ class oci_native_moodle_database extends moodle_database {
if (isset($value['clob'])) {
$lob = oci_new_descriptor($this->oci, OCI_DTYPE_LOB);
oci_bind_by_name($stmt, $key, $lob, -1, SQLT_CLOB);
$lob->writeTemporary($params[$key]['clob'], OCI_TEMP_CLOB);
$lob->writeTemporary($this->oracle_dirty_hack($tablename, $key, $params[$key]['clob']), OCI_TEMP_CLOB);
$descriptors[] = $lob;
continue; // Column binding finished, go to next one
} else if (isset($value['blob'])) {
@ -735,8 +755,8 @@ class oci_native_moodle_database extends moodle_database {
if (strlen($value) > 4000) {
// TODO: Shouldn't arrive here ever! BIG Clobs already bound above. Exception!
}
default: // Bind as CHAR
oci_bind_by_name($stmt, $key, $params[$key]);
default: // Bind as CHAR (applying dirty hack)
oci_bind_by_name($stmt, $key, $this->oracle_dirty_hack($tablename, $key, $params[$key]));
}
}
}
@ -1344,14 +1364,10 @@ class oci_native_moodle_database extends moodle_database {
}
public function sql_isempty($tablename, $fieldname, $nullablefield, $textfield) {
if ($nullablefield) {
return " $fieldname IS NULL "; /// empties in nullable fields are stored as
} else { /// NULLs
if ($textfield) {
return " ".$this->sql_compare_text($fieldname)." = ' ' "; /// oracle_dirty_hack inserts 1-whitespace
} else { /// in NOT NULL varchar and text columns so
return " $fieldname = ' ' "; /// we need to look for that in any situation
}
if ($textfield) {
return " ".$this->sql_compare_text($fieldname)." = '".$this->sql_empty()."' ";
} else {
return " $fieldname = '".$this->sql_empty()."' ";
}
}
@ -1359,6 +1375,10 @@ class oci_native_moodle_database extends moodle_database {
return ' ';
}
public function sql_order_by_text($fieldname, $numchars=32) {
return 'dbms_lob.substr(' . $fieldname . ', ' . $numchars . ',1)';
}
/// session locking
// http://download.oracle.com/docs/cd/B10501_01/appdev.920/a96612/d_lock2.htm#999576
@ -1373,14 +1393,7 @@ class oci_native_moodle_database extends moodle_database {
if (!parent::begin_sql()) {
return false;
}
return true;
$sql = "BEGIN";
$this->query_start($sql, NULL, SQL_QUERY_AUX);
$stmt = $this->parse_query($sql);
$result = oci_execute($stmt, $this->commit_status);
$this->query_end($result, $stmt);
oci_free_statement($stmt);
$this->commit_status = OCI_DEFAULT; //Done! ;-)
return true;
}
@ -1391,14 +1404,11 @@ class oci_native_moodle_database extends moodle_database {
if (!parent::commit_sql()) {
return false;
}
return true;
$sql = "COMMIT";
$this->query_start($sql, NULL, SQL_QUERY_AUX);
$stmt = $this->parse_query($sql);
$result = oci_execute($stmt, $this->commit_status);
$this->query_end($result, $stmt);
oci_free_statement($stmt);
$this->query_start('--oracle_commit', NULL, SQL_QUERY_AUX);
$result = oci_commit($this->oci);
$this->commit_status = OCI_COMMIT_ON_SUCCESS;
$this->query_end($result);
return true;
}
@ -1409,14 +1419,11 @@ class oci_native_moodle_database extends moodle_database {
if (!parent::rollback_sql()) {
return false;
}
return true;
$sql = "ROLLBACK";
$this->query_start($sql, NULL, SQL_QUERY_AUX);
$stmt = $this->parse_query($sql);
$result = oci_execute($stmt, $this->commit_status);
$this->query_end($result, $stmt);
oci_free_statement($stmt);
$this->query_start('--oracle_rollback', NULL, SQL_QUERY_AUX);
$result = oci_rollback($this->oci);
$this->commit_status = OCI_COMMIT_ON_SUCCESS;
$this->query_end($result);
return true;
}
}