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Support date arithmetic with INTERVAL operators #539

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Merged
JanJakes merged 5 commits into from
Oct 21, 2026
Merged

Support date arithmetic with INTERVAL operators #539

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5b2a951
Translate date arithmetic written with INTERVAL operators
samuelmbabhazi Sep 20, 2026
c0b12b1
Reject the prefix INTERVAL form
JanJakes Oct 19, 2026
3996f2d
Reject INTERVAL on a partial operand
JanJakes Oct 19, 2026
5b7787c
Map INTERVAL units by token type
JanJakes Oct 19, 2026
bc9ea36
Return a date for date-only interval arithmetic
JanJakes Oct 20, 2026
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165 changes: 154 additions & 11 deletions packages/mysql-on-sqlite/src/sqlite/class-wp-mysql-on-sqlite.php
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Original file line number Diff line number Diff line change
Expand Up @@ -330,6 +330,23 @@ class WP_MySQL_On_SQLite extends PDO {
'%y' => '%y',
);

/**
* Map MySQL INTERVAL units to SQLite units and value multipliers.
*
* MICROSECOND is excluded because DATETIME() drops fractional seconds.
* Composite units, such as HOUR_MINUTE, are not supported.
*/
private const INTERVAL_UNIT_MAP = array(
WP_MySQL_Lexer::SECOND_SYMBOL => array( 'SECOND', 1 ),
WP_MySQL_Lexer::MINUTE_SYMBOL => array( 'MINUTE', 1 ),
WP_MySQL_Lexer::HOUR_SYMBOL => array( 'HOUR', 1 ),
WP_MySQL_Lexer::DAY_SYMBOL => array( 'DAY', 1 ),
WP_MySQL_Lexer::WEEK_SYMBOL => array( 'DAY', 7 ),
WP_MySQL_Lexer::MONTH_SYMBOL => array( 'MONTH', 1 ),
WP_MySQL_Lexer::QUARTER_SYMBOL => array( 'MONTH', 3 ),
WP_MySQL_Lexer::YEAR_SYMBOL => array( 'YEAR', 1 ),
);

/**
* A map of MySQL data types to implicit default values for non-strict mode.
*
Expand Down Expand Up @@ -4349,6 +4366,8 @@ private function translate( $node ): ?string {
return null;
}
return $this->translate_sequence( $node->get_children() );
case 'bitExpr':
return $this->translate_bit_expr( $node );
case 'simpleExprBody':
return $this->translate_simple_expr_body( $node );
case 'predicateOperations':
Expand Down Expand Up @@ -4915,9 +4934,86 @@ private function translate_simple_expr_body( WP_Parser_Node $node ): string {
}
}

/*
* Reject "INTERVAL n unit + expr": the parser includes following AND, OR,
* and XOR conditions in "expr", unlike MySQL. It also reads
* "expr + INTERVAL 1 DAY + x" as "expr + (INTERVAL 1 DAY + x)".
*
* TODO: Support prefix intervals after switching to the LALR(1) parser.
*/
if ( null !== $token && WP_MySQL_Lexer::INTERVAL_SYMBOL === $token->id ) {
throw $this->new_not_supported_exception(
'INTERVAL n unit followed by "+"; use "(expr + INTERVAL n unit)" instead'
);
}

return $this->translate_sequence( $node->get_children() );
}

/**
* Translate a "bitExpr" AST node.
*
* Translate interval additions and subtractions to a single date function
* call, applying each interval from left to right, as MySQL does.
*
* TODO: After switching to LALR(1), use the tree's operator grouping
* and remove the loop over this parser's flat interval sequence.
*
* @param WP_Parser_Node $node The "bitExpr" AST node.
* @return string|null The translated value.
* @throws WP_MySQL_On_SQLite_Exception When the translation fails.
*/
private function translate_bit_expr( WP_Parser_Node $node ): ?string {
/*
* The first child is an expression. Each interval adds four children:
* operator, INTERVAL, value, unit. A final "op bitExpr" may follow.
*/
$children = $node->get_children();
$count = count( $children );
$sql = $this->translate( $children[0] );
$intervals = array();
$i = 1;
while (
isset( $children[ $i + 1 ] )
&& $children[ $i + 1 ] instanceof WP_Parser_Token
&& WP_MySQL_Lexer::INTERVAL_SYMBOL === $children[ $i + 1 ]->id
) {
$intervals[] = array(
WP_MySQL_Lexer::MINUS_OPERATOR === $children[ $i ]->id,
$children[ $i + 2 ],
$children[ $i + 3 ],
);
$i += 4;
}
if ( count( $intervals ) > 0 ) {
$sql = $this->translate_interval_arithmetic( $sql, $intervals );
}

if ( $i === $count ) {
return $sql;
}

/*
* The parser groups "a + b + INTERVAL 1 DAY" as "a + (b + INTERVAL 1 DAY)".
* MySQL applies the interval to "a + b". Reject this form to avoid
* applying the interval to only part of the expression. For simplicity,
* also reject operators that bind less tightly than "+", such as "|".
*
* TODO: Remove this guard and support mixed arithmetic with LALR(1).
*/
$operator = $children[ $i ];
$operand = $children[ $i + 1 ];
if ( $operand->has_child_token( WP_MySQL_Lexer::INTERVAL_SYMBOL ) ) {
throw $this->new_not_supported_exception(
sprintf(
'INTERVAL after the "%s" operator; add parentheses to make the grouping explicit',
$operator->get_value()
)
);
}
return sprintf( '%s %s %s', $sql, $this->translate( $operator ), $this->translate( $operand ) );
}

/**
* Translate a MySQL CAST expression to SQLite.
*
Expand Down Expand Up @@ -5051,18 +5147,9 @@ private function translate_runtime_function_call( WP_Parser_Node $node ): string
case WP_MySQL_Lexer::DATE_ADD_SYMBOL:
case WP_MySQL_Lexer::DATE_SUB_SYMBOL:
$nodes = $node->get_child_nodes();
$value = $this->translate( $nodes[1] );
$unit = $this->translate( $nodes[2] );
if ( 'WEEK' === $unit ) {
$unit = 'DAY';
$value = 7 * $value;
}
return sprintf(
"DATETIME(%s, '%s' || %s || ' %s')",
return $this->translate_interval_arithmetic(
$this->translate( $nodes[0] ),
WP_MySQL_Lexer::DATE_SUB_SYMBOL === $child->id ? '-' : '+',
$value,
$unit
array( array( WP_MySQL_Lexer::DATE_SUB_SYMBOL === $child->id, $nodes[1], $nodes[2] ) )
);
case WP_MySQL_Lexer::LEFT_SYMBOL:
$nodes = $node->get_child_nodes();
Expand All @@ -5076,6 +5163,62 @@ private function translate_runtime_function_call( WP_Parser_Node $node ): string
}
}

/**
* Translate MySQL date arithmetic to a SQLite DATE() or DATETIME() call.
*
* Each interval becomes a modifier, and SQLite applies them from left to right.
* Parenthesize the value before appending the unit: SQLite evaluates "||"
* before "*". Negate the value for subtraction so negative intervals work
* without invalid sign combinations such as "+-5 HOUR".
* Convert units where needed, e.g., WEEK to 7 days.
*
* MySQL returns a date when it adds only date units to a date. The driver
* stores dates as 10-character strings, so use DATE() for such inputs.
*
* @param string $expr The translated date expression.
* @param array $intervals List of intervals, each as an array of:
* - bool Whether the interval is subtracted.
* - WP_Parser_Node The interval value expression node.
* - WP_Parser_Node The "interval" AST node holding the unit.
* @return string The translated value.
* @throws WP_MySQL_On_SQLite_Exception When the translation fails.
*/
private function translate_interval_arithmetic( string $expr, array $intervals ): string {
$modifiers = array();
$date_units = true;
foreach ( $intervals as list( $subtract, $value, $interval ) ) {
// Token IDs also cover unit synonyms, e.g., SQL_TSI_HOUR.
$unit_token = $interval->get_first_descendant_token();
if ( ! isset( self::INTERVAL_UNIT_MAP[ $unit_token->id ] ) ) {
throw $this->new_not_supported_exception(
sprintf( 'INTERVAL unit: %s', $unit_token->get_value() )
);
}

list( $unit, $multiplier ) = self::INTERVAL_UNIT_MAP[ $unit_token->id ];

$value_sql = sprintf( '(%s)', $this->translate( $value ) );
if ( 1 !== $multiplier ) {
$value_sql = sprintf( '(%s * %d)', $value_sql, $multiplier );
}
if ( $subtract ) {
$value_sql = '-' . $value_sql;
}
$modifiers[] = sprintf( "%s || ' %s'", $value_sql, $unit );
$date_units = $date_units && in_array( $unit, array( 'DAY', 'MONTH', 'YEAR' ), true );
}

$modifiers_sql = implode( ', ', $modifiers );
if ( ! $date_units ) {
return sprintf( 'DATETIME(%s, %s)', $expr, $modifiers_sql );
}
return sprintf(
'CASE WHEN LENGTH(%1$s) = 10 THEN DATE(%1$s, %2$s) ELSE DATETIME(%1$s, %2$s) END',
$expr,
$modifiers_sql
);
}

/**
* Translate a MySQL function call to SQLite.
*
Expand Down
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