is_blog_installed(): bool

1772function is_blog_installed() {1773	global $wpdb;1774 1775	/*1776	 * Check cache first. If options table goes away and we have true1777	 * cached, oh well.1778	 */1779	if ( wp_cache_get( 'is_blog_installed' ) ) {1780		return true;1781	}1782 1783	$suppress = $wpdb->suppress_errors();1784 1785	if ( ! wp_installing() ) {1786		$alloptions = wp_load_alloptions();1787	}1788 1789	// If siteurl is not set to autoload, check it specifically.1790	if ( ! isset( $alloptions['siteurl'] ) ) {1791		$installed = $wpdb->get_var( "SELECT option_value FROM $wpdb->options WHERE option_name = 'siteurl'" );1792	} else {1793		$installed = $alloptions['siteurl'];1794	}1795 1796	$wpdb->suppress_errors( $suppress );1797 1798	$installed = ! empty( $installed );1799	wp_cache_set( 'is_blog_installed', $installed );1800 1801	if ( $installed ) {1802		return true;1803	}1804 1805	// If visiting repair.php, return true and let it take over.1806	if ( defined( 'WP_REPAIRING' ) ) {1807		return true;1808	}1809 1810	$suppress = $wpdb->suppress_errors();1811 1812	/*1813	 * Loop over the WP tables. If none exist, then scratch installation is allowed.1814	 * If one or more exist, suggest table repair since we got here because the1815	 * options table could not be accessed.1816	 */1817	$wp_tables = $wpdb->tables();1818	foreach ( $wp_tables as $table ) {1819		// The existence of custom user tables shouldn't suggest an unwise state or prevent a clean installation.1820		if ( defined( 'CUSTOM_USER_TABLE' ) && CUSTOM_USER_TABLE === $table ) {1821			continue;1822		}1823 1824		if ( defined( 'CUSTOM_USER_META_TABLE' ) && CUSTOM_USER_META_TABLE === $table ) {1825			continue;1826		}1827 1828		$described_table = $wpdb->get_results( "DESCRIBE $table;" );1829		if (1830			( ! $described_table && empty( $wpdb->last_error ) ) ||1831			( is_array( $described_table ) && 0 === count( $described_table ) )1832		) {1833			continue;1834		}1835 1836		// One or more tables exist. This is not good.1837 1838		wp_load_translations_early();1839 1840		// Die with a DB error.1841		$wpdb->error = sprintf(1842			/* translators: %s: Database repair URL. */1843			__( 'One or more database tables are unavailable. The database may need to be <a href="%s">repaired</a>.' ),1844			'maint/repair.php?referrer=is_blog_installed'1845		);1846 1847		dead_db();1848	}1849 1850	$wpdb->suppress_errors( $suppress );1851