maybe_convert_table_to_utf8mb4( string $table ): bool
- Since
- 4.2.0
- Source
wp-admin/includes/upgrade.php:2796
Compatibility
- WordPress
- since 4.2.0
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.
Parameters
$tablestring- The table to convert.
Return value
bool- True if the table was converted, false if it wasn't.
Performance profile
How much work a call to maybe_convert_table_to_utf8mb4() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.
- Cost class
- Heavy
- Scaling
- Scales with input
- Instructions
- 11–41
- Plugin surface
- None
- Called by
- 3
Reaches the database via ->get_results().
The body loops, so the work grows with what you pass in.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 64.
Nothing here hands control to plugin code.
3 places in core call this, so the cost is paid more often than your own code shows.
What it touches
- sqldatabase query
->get_results()called directly
What one call costs · 5 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost maybe_convert_table_to_utf8mb4() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
| always | 11 | ->get_results() |
| always | 21–22 | ->get_results(), ->get_row() |
!$results && $column && $charset !== "utf8" && $charset !== "utf8mb4" | 32 | ->get_results(), explode(), strtolower() |
$table_charset === "utf8mb4" | 34–35 | ->get_results(), ->get_row(), explode(), strtolower() |
$table_charset !== "utf8mb4" | 40–41 | ->get_results(), ->get_row(), explode(), strtolower(), ->query() |
Across PHP versions
Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 64 instructions, 11–41 executed per call, 8 branches. The work does not change between versions.
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Used by · 3
- pre_schema_upgrade()Runs before the schema is upgraded.
- upgrade_430()Executes changes made in WordPress 4.3.0.
- upgrade_network()Executes network-level upgrade routines.
Source code
function maybe_convert_table_to_utf8mb4( $table ) { global $wpdb; $results = $wpdb->get_results( "SHOW FULL COLUMNS FROM `$table`" ); if ( ! $results ) { return false; } foreach ( $results as $column ) { if ( $column->Collation ) { list( $charset ) = explode( '_', $column->Collation ); $charset = strtolower( $charset ); if ( 'utf8' !== $charset && 'utf8mb4' !== $charset ) { // Don't upgrade tables that have non-utf8 columns. return false; } } } $table_details = $wpdb->get_row( "SHOW TABLE STATUS LIKE '$table'" ); if ( ! $table_details ) { return false; } list( $table_charset ) = explode( '_', $table_details->Collation ); $table_charset = strtolower( $table_charset ); if ( 'utf8mb4' === $table_charset ) { return true; } return $wpdb->query( "ALTER TABLE $table CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci" );}Changelog
Introduced in 4.2.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
About this page
- Parsed data
- Generated from the wordpress-develop 7.1.0 tag, from
src/wp-admin/includes/upgrade.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
- Something wrong on this page? Report it and it gets fixed in the next regeneration.