silverstripe-postgresql/code/PostgreSQLSchemaManager.php

<?php

namespace SilverStripe\PostgreSQL;

use SilverStripe\Dev\Deprecation;
use SilverStripe\ORM\Connect\DBSchemaManager;
use SilverStripe\ORM\DB;

/**
 * PostgreSQL schema manager
 *
 * @package sapphire
 * @subpackage model
 */
class PostgreSQLSchemaManager extends DBSchemaManager
{
    /**
     * Identifier for this schema, used for configuring schema-specific table
     * creation options
     */
    const ID = 'PostgreSQL';

    /**
     * Instance of the database controller this schema belongs to
     *
     * @var PostgreSQLDatabase
     */
    protected $database = null;

    /**
     * This holds a copy of all the constraint results that are returned
     * via the function constraintExists().  This is a bit faster than
     * repeatedly querying this column, and should allow the database
     * to use it's built-in caching features for better queries.
     *
     * @var array
     */
    protected static $cached_constraints = array();

    /**
     *
     * This holds a copy of all the queries that run through the function fieldList()
     * This is one of the most-often called functions, and repeats itself a great deal in the unit tests.
     *
     * @var array
     */
    protected static $cached_fieldlists = array();

    protected function indexKey($table, $index, $spec)
    {
        return $this->buildPostgresIndexName($table, $index);
    }

    /**
     * Creates a postgres database, ignoring model_schema_as_database
     *
     * @param string $name
     */
    public function createPostgresDatabase($name)
    {
        $this->query("CREATE DATABASE \"$name\";");
    }

    public function createDatabase($name)
    {
        if (PostgreSQLDatabase::model_schema_as_database()) {
            $schemaName = $this->database->databaseToSchemaName($name);
            return $this->createSchema($schemaName);
        }
        return $this->createPostgresDatabase($name);
    }

    /**
     * Determines if a postgres database exists, ignoring model_schema_as_database
     *
     * @param string $name
     * @return boolean
     */
    public function postgresDatabaseExists($name)
    {
        $result = $this->preparedQuery("SELECT datname FROM pg_database WHERE datname = ?;", array($name));
        return $result->first() ? true : false;
    }

    public function databaseExists($name)
    {
        if (PostgreSQLDatabase::model_schema_as_database()) {
            $schemaName = $this->database->databaseToSchemaName($name);
            return $this->schemaExists($schemaName);
        }
        return $this->postgresDatabaseExists($name);
    }

    /**
     * Determines the list of all postgres databases, ignoring model_schema_as_database
     *
     * @return array
     */
    public function postgresDatabaseList()
    {
        return $this->query("SELECT datname FROM pg_database WHERE datistemplate=false;")->column();
    }

    public function databaseList()
    {
        if (PostgreSQLDatabase::model_schema_as_database()) {
            $schemas = $this->schemaList();
            $names = array();
            foreach ($schemas as $schema) {
                $names[] = $this->database->schemaToDatabaseName($schema);
            }
            return array_unique($names);
        }
        return $this->postgresDatabaseList();
    }

    /**
     * Drops a postgres database, ignoring model_schema_as_database
     *
     * @param string $name
     */
    public function dropPostgresDatabase($name)
    {
        $nameSQL = $this->database->escapeIdentifier($name);
        $this->query("DROP DATABASE $nameSQL;");
    }

    public function dropDatabase($name)
    {
        if (PostgreSQLDatabase::model_schema_as_database()) {
            $schemaName = $this->database->databaseToSchemaName($name);
            $this->dropSchema($schemaName);
            return;
        }
        $this->dropPostgresDatabase($name);
    }

    /**
     * Returns true if the schema exists in the current database
     *
     * @param string $name
     * @return boolean
     */
    public function schemaExists($name)
    {
        return $this->preparedQuery(
            "SELECT nspname FROM pg_catalog.pg_namespace WHERE nspname = ?;",
            array($name)
        )->first() ? true : false;
    }

    /**
     * Creates a schema in the current database
     *
     * @param string $name
     */
    public function createSchema($name)
    {
        $nameSQL = $this->database->escapeIdentifier($name);
        $this->query("CREATE SCHEMA $nameSQL;");
    }

    /**
     * Drops a schema from the database. Use carefully!
     *
     * @param string $name
     */
    public function dropSchema($name)
    {
        $nameSQL = $this->database->escapeIdentifier($name);
        $this->query("DROP SCHEMA $nameSQL CASCADE;");
    }

    /**
     * Returns the list of all available schemas on the current database
     *
     * @return array
     */
    public function schemaList()
    {
        return $this->query(
            "SELECT nspname
            FROM pg_catalog.pg_namespace
            WHERE nspname <> 'information_schema' AND nspname !~ E'^pg_'"
        )->column();
    }

    public function createTable($table, $fields = null, $indexes = null, $options = null, $advancedOptions = null)
    {
        $fieldSchemas = "";
        if ($fields) {
            foreach ($fields as $k => $v) {
                $fieldSchemas .= "\"$k\" $v,\n";
            }
        }
        if (!empty($options[self::ID])) {
            $addOptions = $options[self::ID];
        } else {
            $addOptions = null;
        }

        //First of all, does this table already exist
        $doesExist = $this->hasTable($table);
        if ($doesExist) {
            // Table already exists, just return the name, in line with baseclass documentation.
            return $table;
        }

        //If we have a fulltext search request, then we need to create a special column
        //for GiST searches
        $fulltexts = '';
        $triggers = [];
        if ($indexes) {
            foreach ($indexes as $name => $this_index) {
                if (is_array($this_index) && $this_index['type'] == 'fulltext') {
                    $ts_details = $this->fulltext($this_index, $table, $name);
                    $fulltexts .= $ts_details['fulltexts'] . ', ';
                    $triggers[] = $ts_details['triggers'];
                }
            }
        }

        $indexQueries = [];
        if ($indexes) {
            foreach ($indexes as $k => $v) {
                $indexQueries[] = $this->getIndexSqlDefinition($table, $k, $v);
            }
        }

        //Do we need to create a tablespace for this item?
        if ($advancedOptions && isset($advancedOptions['tablespace'])) {
            $this->createOrReplaceTablespace(
                $advancedOptions['tablespace']['name'],
                $advancedOptions['tablespace']['location']
            );
            $tableSpace = ' TABLESPACE ' . $advancedOptions['tablespace']['name'];
        } else {
            $tableSpace = '';
        }

        $this->query(
            "CREATE TABLE \"$table\" (
                $fieldSchemas
                $fulltexts
                primary key (\"ID\")
            )$tableSpace $addOptions"
        );
        foreach ($indexQueries as $indexQuery) {
            $this->query($indexQuery);
        }

        foreach ($triggers as $trigger) {
            $this->query($trigger);
        }

        //If we have a partitioning requirement, we do that here:
        if ($advancedOptions && isset($advancedOptions['partitions'])) {
            $this->createOrReplacePartition($table, $advancedOptions['partitions'], $indexes, $advancedOptions);
        }

        //Lastly, clustering goes here:
        if ($advancedOptions && isset($advancedOptions['cluster'])) {
            $this->query("CLUSTER \"$table\" USING \"{$advancedOptions['cluster']}\"");
        }

        return $table;
    }

    /**
     * Builds the internal Postgres index name given the silverstripe table and index name
     *
     * @param string $tableName
     * @param string $indexName
     * @param string $prefix The optional prefix for the index. Defaults to "ix" for indexes.
     * @return string The postgres name of the index
     */
    protected function buildPostgresIndexName($tableName, $indexName, $prefix = 'ix')
    {

        // Assume all indexes also contain the table name
        // MD5 the table/index name combo to keep it to a fixed length.
        // Exclude the prefix so that the trigger name can be easily generated from the index name
        $indexNamePG = "{$prefix}_" . md5("{$tableName}_{$indexName}");

        // Limit to 63 characters
        if (strlen($indexNamePG) > 63) {
            return substr($indexNamePG, 0, 63);
        } else {
            return $indexNamePG;
        }
    }

    /**
     * Builds the internal Postgres trigger name given the silverstripe table and trigger name
     *
     * @param string $tableName
     * @param string $triggerName
     * @return string The postgres name of the trigger
     */
    public function buildPostgresTriggerName($tableName, $triggerName)
    {
        // Kind of cheating, but behaves the same way as indexes
        return $this->buildPostgresIndexName($tableName, $triggerName, 'ts');
    }

    public function alterTable(
        $table,
        $newFields = null,
        $newIndexes = null,
        $alteredFields = null,
        $alteredIndexes = null,
        $alteredOptions = null,
        $advancedOptions = null
    ) {
        $alterList = [];
        if ($newFields) {
            foreach ($newFields as $fieldName => $fieldSpec) {
                $alterList[] = "ADD \"$fieldName\" $fieldSpec";
            }
        }

        if ($alteredFields) {
            foreach ($alteredFields as $indexName => $indexSpec) {
                $val = $this->alterTableAlterColumn($table, $indexName, $indexSpec);
                if (!empty($val)) {
                    $alterList[] = $val;
                }
            }
        }

        //Do we need to do anything with the tablespaces?
        if ($alteredOptions && isset($advancedOptions['tablespace'])) {
            $this->createOrReplaceTablespace(
                $advancedOptions['tablespace']['name'],
                $advancedOptions['tablespace']['location']
            );
            $this->query("ALTER TABLE \"$table\" SET TABLESPACE {$advancedOptions['tablespace']['name']};");
        }

        //DB ABSTRACTION: we need to change the constraints to be a separate 'add' command,
        //see http://www.postgresql.org/docs/8.1/static/sql-altertable.html
        $alterIndexList = [];
        //Pick up the altered indexes here:
        $fieldList = $this->fieldList($table);
        $fulltexts = [];
        $dropTriggers = [];
        $triggers = [];
        if ($alteredIndexes) {
            foreach ($alteredIndexes as $indexName => $indexSpec) {
                $indexNamePG = $this->buildPostgresIndexName($table, $indexName);

                if ($indexSpec['type'] == 'fulltext') {
                    //For full text indexes, we need to drop the trigger, drop the index, AND drop the column

                    //Go and get the tsearch details:
                    $ts_details = $this->fulltext($indexSpec, $table, $indexName);

                    //Drop this column if it already exists:

                    //No IF EXISTS option is available for Postgres <9.0
                    if (array_key_exists($ts_details['ts_name'], $fieldList)) {
                        $fulltexts[] = "ALTER TABLE \"{$table}\" DROP COLUMN \"{$ts_details['ts_name']}\";";
                    }

                    // We'll execute these later:
                    $triggerNamePG = $this->buildPostgresTriggerName($table, $indexName);
                    $dropTriggers[] = "DROP TRIGGER IF EXISTS \"$triggerNamePG\" ON \"$table\";";
                    $fulltexts[] = "ALTER TABLE \"{$table}\" ADD COLUMN {$ts_details['fulltexts']};";
                    $triggers[] = $ts_details['triggers'];
                }

                // Create index action (including fulltext)
                $alterIndexList[] = "DROP INDEX IF EXISTS \"$indexNamePG\";";
                $createIndex = $this->getIndexSqlDefinition($table, $indexName, $indexSpec);
                if ($createIndex) {
                    $alterIndexList[] = $createIndex;
                }
            }
        }

        //Add the new indexes:
        if ($newIndexes) {
            foreach ($newIndexes as $indexName => $indexSpec) {
                $indexNamePG = $this->buildPostgresIndexName($table, $indexName);
                //If we have a fulltext search request, then we need to create a special column
                //for GiST searches
                //Pick up the new indexes here:
                if ($indexSpec['type'] == 'fulltext') {
                    $ts_details = $this->fulltext($indexSpec, $table, $indexName);
                    if (!isset($fieldList[$ts_details['ts_name']])) {
                        $fulltexts[] = "ALTER TABLE \"{$table}\" ADD COLUMN {$ts_details['fulltexts']};";
                        $triggers[] = $ts_details['triggers'];
                    }
                }

                //Check that this index doesn't already exist:
                $indexes = $this->indexList($table);
                if (isset($indexes[$indexName])) {
                    $alterIndexList[] = "DROP INDEX IF EXISTS \"$indexNamePG\";";
                }

                $createIndex = $this->getIndexSqlDefinition($table, $indexName, $indexSpec);
                if ($createIndex) {
                    $alterIndexList[] = $createIndex;
                }
            }
        }

        if ($alterList) {
            $alterations = implode(",\n", $alterList);
            $this->query("ALTER TABLE \"$table\" " . $alterations);
        }

        //Do we need to create a tablespace for this item?
        if ($advancedOptions && isset($advancedOptions['extensions']['tablespace'])) {
            $extensions = $advancedOptions['extensions'];
            $this->createOrReplaceTablespace($extensions['tablespace']['name'], $extensions['tablespace']['location']);
        }

        if ($alteredOptions && isset($this->class) && isset($alteredOptions[$this->class])) {
            $this->query(sprintf("ALTER TABLE \"%s\" %s", $table, $alteredOptions[$this->class]));
            DB::alteration_message(
                sprintf("Table %s options changed: %s", $table, $alteredOptions[$this->class]),
                "changed"
            );
        }

        //Create any fulltext columns and triggers here:
        foreach ($fulltexts as $fulltext) {
            $this->query($fulltext);
        }
        foreach ($dropTriggers as $dropTrigger) {
            $this->query($dropTrigger);
        }

        foreach ($triggers as $trigger) {
            $this->query($trigger);
            $triggerFields = $this->triggerFieldsFromTrigger($trigger);
            if ($triggerFields) {
                //We need to run a simple query to force the database to update the triggered columns
                $this->query("UPDATE \"{$table}\" SET \"{$triggerFields[0]}\"=\"$triggerFields[0]\";");
            }
        }

        foreach ($alterIndexList as $alteration) {
            $this->query($alteration);
        }

        //If we have a partitioning requirement, we do that here:
        if ($advancedOptions && isset($advancedOptions['partitions'])) {
            $this->createOrReplacePartition($table, $advancedOptions['partitions']);
        }

        //Lastly, clustering goes here:
        if ($advancedOptions && isset($advancedOptions['cluster'])) {
            $clusterIndex = $this->buildPostgresIndexName($table, $advancedOptions['cluster']);
            $this->query("CLUSTER \"$table\" USING \"$clusterIndex\";");
        } else {
            //Check that clustering is not on this table, and if it is, remove it:

            //This is really annoying.  We need the oid of this table:
            $stats = $this->preparedQuery(
                "SELECT relid FROM pg_stat_user_tables WHERE relname = ?;",
                array($table)
            )->first();
            $oid = $stats['relid'];

            //Now we can run a long query to get the clustered status:
            //If anyone knows a better way to get the clustered status, then feel free to replace this!
            $clustered = $this->preparedQuery(
                "
                SELECT c2.relname, i.indisclustered 
                FROM pg_catalog.pg_class c, pg_catalog.pg_class c2, pg_catalog.pg_index i
                WHERE c.oid = ? AND c.oid = i.indrelid AND i.indexrelid = c2.oid AND indisclustered='t';",
                array($oid)
            )->first();

            if ($clustered) {
                $this->query("ALTER TABLE \"$table\" SET WITHOUT CLUSTER;");
            }
        }
    }

    /*
     * Creates an ALTER expression for a column in PostgreSQL
     *
     * @param $tableName Name of the table to be altered
     * @param $colName   Name of the column to be altered
     * @param $colSpec   String which contains conditions for a column
     * @return string
     */
    private function alterTableAlterColumn($tableName, $colName, $colSpec)
    {
        // First, we split the column specifications into parts
        // TODO: this returns an empty array for the following string: int(11) not null auto_increment
        //         on second thoughts, why is an auto_increment field being passed through?

        $pattern = '/^([\w(\,)]+)\s?((?:not\s)?null)?\s?(default\s[\w\.\']+)?\s?(check\s[\w()\'",\s]+)?$/i';
        preg_match($pattern, $colSpec, $matches);

        if (sizeof($matches) == 0) {
            return '';
        }

        if ($matches[1] == 'serial8') {
            return '';
        }

        if (isset($matches[1])) {
            $alterCol = "ALTER COLUMN \"$colName\" TYPE $matches[1] USING \"$colName\"::$matches[1]\n";

            // SET null / not null
            if (!empty($matches[2])) {
                $alterCol .= ",\nALTER COLUMN \"$colName\" SET $matches[2]";
            }

            // SET default (we drop it first, for reasons of precaution)
            if (!empty($matches[3])) {
                $alterCol .= ",\nALTER COLUMN \"$colName\" DROP DEFAULT";
                $alterCol .= ",\nALTER COLUMN \"$colName\" SET $matches[3]";
            }

            // SET check constraint (The constraint HAS to be dropped)
            $constraintName = "{$tableName}_{$colName}_check";
            $constraintExists = $this->constraintExists($constraintName, false);
            if (isset($matches[4])) {
                //Take this new constraint and see what's outstanding from the target table:
                $constraint_bits = explode('(', $matches[4]);
                $constraint_values = trim($constraint_bits[2], ')');
                $constraint_values_bits = explode(',', $constraint_values);
                $default = trim($constraint_values_bits[0], " '");

                //Now go and convert anything that's not in this list to 'Page'
                //We have to run this as a query, not as part of the alteration queries due to the way they are constructed.
                $updateConstraint = '';
                $updateConstraint .= "UPDATE \"{$tableName}\" SET \"$colName\"='$default' WHERE \"$colName\" NOT IN ($constraint_values);";
                if ($this->hasTable("{$tableName}_Live")) {
                    $updateConstraint .= "UPDATE \"{$tableName}_Live\" SET \"$colName\"='$default' WHERE \"$colName\" NOT IN ($constraint_values);";
                }
                if ($this->hasTable("{$tableName}_versions")) {
                    $updateConstraint .= "UPDATE \"{$tableName}_versions\" SET \"$colName\"='$default' WHERE \"$colName\" NOT IN ($constraint_values);";
                }

                $this->query($updateConstraint);
            }

            //First, delete any existing constraint on this column, even if it's no longer an enum
            if ($constraintExists) {
                $alterCol .= ",\nDROP CONSTRAINT \"{$constraintName}\"";
            }

            //Now create the constraint (if we've asked for one)
            if (!empty($matches[4])) {
                $alterCol .= ",\nADD CONSTRAINT \"{$constraintName}\" $matches[4]";
            }
        }

        return isset($alterCol) ? $alterCol : '';
    }

    public function renameTable($oldTableName, $newTableName)
    {
        $this->query("ALTER TABLE \"$oldTableName\" RENAME TO \"$newTableName\"");
        unset(self::$cached_fieldlists[$oldTableName]);
    }

    public function checkAndRepairTable($tableName)
    {
        $this->query("VACUUM FULL ANALYZE \"$tableName\"");
        $this->query("REINDEX TABLE \"$tableName\"");
        return true;
    }

    public function createField($table, $field, $spec)
    {
        $this->query("ALTER TABLE \"$table\" ADD \"$field\" $spec");
    }

    /**
     * Change the database type of the given field.
     *
     * @param string $tableName The name of the tbale the field is in.
     * @param string $fieldName The name of the field to change.
     * @param string $fieldSpec The new field specification
     */
    public function alterField($tableName, $fieldName, $fieldSpec)
    {
        $this->query("ALTER TABLE \"$tableName\" CHANGE \"$fieldName\" \"$fieldName\" $fieldSpec");
    }

    public function renameField($tableName, $oldName, $newName)
    {
        $fieldList = $this->fieldList($tableName);
        if (array_key_exists($oldName, $fieldList)) {
            $this->query("ALTER TABLE \"$tableName\" RENAME COLUMN \"$oldName\" TO \"$newName\"");

            //Remove this from the cached list:
            unset(self::$cached_fieldlists[$tableName]);
        }
    }

    public function fieldList($table)
    {
        //Query from http://www.alberton.info/postgresql_meta_info.html
        //This gets us more information than we need, but I've included it all for the moment....

        //if(!isset(self::$cached_fieldlists[$table])){
        $fields = $this->preparedQuery(
            "
                SELECT ordinal_position, column_name, data_type, column_default,
                is_nullable, character_maximum_length, numeric_precision, numeric_scale
                FROM information_schema.columns WHERE table_name = ? and table_schema = ?
                ORDER BY ordinal_position;",
            array($table, $this->database->currentSchema())
        );

        $output = array();
        if ($fields) {
            foreach ($fields as $field) {
                switch ($field['data_type']) {
                    case 'character varying':
                        //Check to see if there's a constraint attached to this column:
                        //$constraint=$this->query("SELECT conname,pg_catalog.pg_get_constraintdef(r.oid, true) FROM pg_catalog.pg_constraint r WHERE r.contype = 'c' AND conname='" . $table . '_' . $field['column_name'] . "_check' ORDER BY 1;")->first();
                        $constraint = $this->constraintExists($table . '_' . $field['column_name'] . '_check');
                        if ($constraint) {
                            //Now we need to break this constraint text into bits so we can see what we have:
                            //Examples:
                            //CHECK ("CanEditType"::text = ANY (ARRAY['LoggedInUsers'::character varying, 'OnlyTheseUsers'::character varying, 'Inherit'::character varying]::text[]))
                            //CHECK ("ClassName"::text = 'PageComment'::text)

                            //TODO: replace all this with a regular expression!
                            $value = $constraint['pg_get_constraintdef'];
                            $value = substr($value, strpos($value, '='));
                            $value = str_replace("''", "'", $value);

                            $in_value = false;
                            $constraints = array();
                            $current_value = '';
                            for ($i = 0; $i < strlen($value); $i++) {
                                $char = substr($value, $i, 1);
                                if ($in_value) {
                                    $current_value .= $char;
                                }

                                if ($char == "'") {
                                    if (!$in_value) {
                                        $in_value = true;
                                    } else {
                                        $in_value = false;
                                        $constraints[] = substr($current_value, 0, -1);
                                        $current_value = '';
                                    }
                                }
                            }

                            if (sizeof($constraints) > 0) {
                                //Get the default:
                                $default = trim(substr(
                                    $field['column_default'],
                                    0,
                                    strpos($field['column_default'], '::')
                                ), "'");
                                $output[$field['column_name']] = $this->enum(array(
                                    'default' => $default,
                                    'name' => $field['column_name'],
                                    'enums' => $constraints
                                ));
                            }
                        } else {
                            $output[$field['column_name']] = 'varchar(' . $field['character_maximum_length'] . ')';
                        }
                        break;

                    case 'numeric':
                        $output[$field['column_name']] = 'decimal(' . $field['numeric_precision'] . ',' . $field['numeric_scale'] . ') default ' . floatval($field['column_default']);
                        break;

                    case 'integer':
                        $output[$field['column_name']] = 'integer default ' . (int)$field['column_default'];
                        break;

                    case 'timestamp without time zone':
                        $output[$field['column_name']] = 'timestamp';
                        break;

                    case 'smallint':
                        $output[$field['column_name']] = 'smallint default ' . (int)$field['column_default'];
                        break;

                    case 'time without time zone':
                        $output[$field['column_name']] = 'time';
                        break;

                    case 'double precision':
                        $output[$field['column_name']] = 'float';
                        break;

                    default:
                        $output[$field['column_name']] = $field;
                }
            }
        }

        //    self::$cached_fieldlists[$table]=$output;
        //}

        //return self::$cached_fieldlists[$table];

        return $output;
    }

    public function clearCachedFieldlist($tableName = false)
    {
        if ($tableName) {
            unset(self::$cached_fieldlists[$tableName]);
        } else {
            self::$cached_fieldlists = array();
        }
        return true;
    }

    /**
     * Create an index on a table.
     *
     * @param string $tableName The name of the table.
     * @param string $indexName The name of the index.
     * @param string $indexSpec The specification of the index, see Database::requireIndex() for more details.
     */
    public function createIndex($tableName, $indexName, $indexSpec)
    {
        $createIndex = $this->getIndexSqlDefinition($tableName, $indexName, $indexSpec);
        if ($createIndex !== false) {
            $this->query($createIndex);
        }
    }

    protected function getIndexSqlDefinition($tableName, $indexName, $indexSpec)
    {

        //TODO: create table partition support
        //TODO: create clustering options

        //NOTE: it is possible for *_renamed tables to have indexes whose names are not updates
        //Therefore, we now check for the existance of indexes before we create them.
        //This is techically a bug, since new tables will not be indexed.

        // Determine index name
        $tableCol = $this->buildPostgresIndexName($tableName, $indexName);

        //Misc options first:
        $fillfactor = $where = '';
        if (isset($indexSpec['fillfactor'])) {
            $fillfactor = 'WITH (FILLFACTOR = ' . $indexSpec['fillfactor'] . ')';
        }
        if (isset($indexSpec['where'])) {
            $where = 'WHERE ' . $indexSpec['where'];
        }

        //create a type-specific index
        // NOTE:  hash should be removed.  This is only here to demonstrate how other indexes can be made
        // NOTE: Quote the index name to preserve case sensitivity
        switch ($indexSpec['type']) {
            case 'fulltext':
                // @see fulltext() for the definition of the trigger that ts_$IndexName uses for fulltext searching
                $clusterMethod = PostgreSQLDatabase::default_fts_cluster_method();
                $spec = "create index \"$tableCol\" ON \"$tableName\" USING $clusterMethod(\"ts_" . $indexName . "\") $fillfactor $where";
                break;

            case 'unique':
                $spec = "create unique index \"$tableCol\" ON \"$tableName\" (" . $this->implodeColumnList($indexSpec['columns']) . ") $fillfactor $where";
                break;

            case 'btree':
                $spec = "create index \"$tableCol\" ON \"$tableName\" USING btree (" . $this->implodeColumnList($indexSpec['columns']) . ") $fillfactor $where";
                break;

            case 'hash':
                //NOTE: this is not a recommended index type
                $spec = "create index \"$tableCol\" ON \"$tableName\" USING hash (" . $this->implodeColumnList($indexSpec['columns']) . ") $fillfactor $where";
                break;

            case 'index':
                //'index' is the same as default, just a normal index with the default type decided by the database.
            default:
                $spec = "create index \"$tableCol\" ON \"$tableName\" (" . $this->implodeColumnList($indexSpec['columns']) . ") $fillfactor $where";
        }
        return trim($spec) . ';';
    }

    public function alterIndex($tableName, $indexName, $indexSpec)
    {
        $indexSpec = trim($indexSpec);
        if ($indexSpec[0] != '(') {
            list($indexType, $indexFields) = explode(' ', $indexSpec, 2);
        } else {
            $indexType = null;
            $indexFields = $indexSpec;
        }

        if (!$indexType) {
            $indexType = "index";
        }

        $this->query("DROP INDEX \"$indexName\"");
        $this->query("ALTER TABLE \"$tableName\" ADD $indexType \"$indexName\" $indexFields");
    }

    /**
     * Given a trigger name attempt to determine the columns upon which it acts
     *
     * @param string $triggerName Postgres trigger name
     * @param string $table
     * @return array List of columns
     */
    protected function extractTriggerColumns($triggerName, $table)
    {
        $trigger = $this->preparedQuery(
            "SELECT t.tgargs 
            FROM pg_catalog.pg_trigger t
            INNER JOIN pg_catalog.pg_class c ON c.oid = t.tgrelid 
            INNER JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
            WHERE c.relname = ?
                AND n.nspname = ?
                AND t.tgname = ?",
            [
                $table,
                $this->database->currentSchema(),
                $triggerName
            ]
        )->first();

        // Convert stream to string
        if (is_resource($trigger['tgargs'])) {
            $trigger['tgargs'] = stream_get_contents($trigger['tgargs']);
        }

        if (strpos($trigger['tgargs'], "\000") !== false) {
            // Option 1: output as a string (PDO)
            $argList = array_filter(explode("\000", $trigger['tgargs']));
        } else {
            // Option 2: hex-encoded (pg_sql non-pdo)
            $bytes = str_split($trigger['tgargs'], 2);
            $argList = array();
            $nextArg = "";
            foreach ($bytes as $byte) {
                if ($byte == "00") {
                    $argList[] = $nextArg;
                    $nextArg = "";
                } else {
                    $nextArg .= chr(hexdec($byte));
                }
            }
        }

        // Drop first two arguments (trigger name and config name) and implode into nice list
        return array_slice($argList, 2);
    }

    public function indexList($table)
    {
        //Retrieve a list of indexes for the specified table
        $indexes = $this->preparedQuery(
            "
            SELECT tablename, indexname, indexdef
            FROM pg_catalog.pg_indexes
            WHERE tablename = ? AND schemaname = ?;",
            array($table, $this->database->currentSchema())
        );

        $indexList = array();
        foreach ($indexes as $index) {
            // Key for the indexList array.  Differs from other DB implementations, which is why
            // requireIndex() needed to be overridden
            $indexName = $index['indexname'];

            //We don't actually need the entire created command, just a few bits:
            $type = '';

            //Check for uniques:
            if (substr($index['indexdef'], 0, 13) == 'CREATE UNIQUE') {
                $type = 'unique';
            }

            //check for hashes, btrees etc:
            if (strpos(strtolower($index['indexdef']), 'using hash ') !== false) {
                $type = 'hash';
            }

            //TODO: Fix me: btree is the default index type:
            //if(strpos(strtolower($index['indexdef']), 'using btree ')!==false)
            //    $prefix='using btree ';

            if (strpos(strtolower($index['indexdef']), 'using rtree ') !== false) {
                $type = 'rtree';
            }

            // For fulltext indexes we need to extract the columns from another source
            if (stristr($index['indexdef'], 'using gin')) {
                $type = 'fulltext';
                // Extract trigger information from postgres
                $triggerName = preg_replace('/^ix_/', 'ts_', $index['indexname']);
                $columns = $this->extractTriggerColumns($triggerName, $table);
                $columnString = $this->implodeColumnList($columns);
            } else {
                $columnString = $this->quoteColumnSpecString($index['indexdef']);
            }

            $indexList[$indexName] = array(
                'name' => $indexName, // Not the correct name in the PHP, as this will be a mangled postgres-unique code
                'columns' => $this->explodeColumnString($columnString),
                'type' => $type ?: 'index',
            );
        }

        return $indexList;
    }

    public function tableList()
    {
        $tables = array();
        $result = $this->preparedQuery(
            "SELECT tablename FROM pg_catalog.pg_tables WHERE schemaname = ? AND tablename NOT ILIKE 'pg\\\_%' AND tablename NOT ILIKE 'sql\\\_%'",
            array($this->database->currentSchema())
        );
        foreach ($result as $record) {
            $table = reset($record);
            $tables[strtolower($table)] = $table;
        }
        return $tables;
    }

    /**
     * Find out what the constraint information is, given a constraint name.
     * We also cache this result, so the next time we don't need to do a
     * query all over again.
     *
     * @param string $constraint
     * @param bool $cache Flag whether a cached version should be used. Set to false to cache bust.
     * @return false|array Either false, if the constraint doesn't exist, or an array
     * with the keys conname and pg_get_constraintdef
     */
    protected function constraintExists($constraint, $cache = true)
    {
        if (!$cache || !isset(self::$cached_constraints[$constraint])) {
            $value = $this->preparedQuery(
                "
                SELECT conname,pg_catalog.pg_get_constraintdef(r.oid, true)
                FROM pg_catalog.pg_constraint r
                INNER JOIN pg_catalog.pg_namespace n
                  ON r.connamespace = n.oid
                WHERE r.contype = 'c' AND conname = ? AND n.nspname = ?
                ORDER BY 1;",
                array($constraint, $this->database->currentSchema())
            )->first();
            if (!$cache) {
                return $value;
            }
            self::$cached_constraints[$constraint] = $value;
        }

        return self::$cached_constraints[$constraint];
    }

    /**
     * A function to return the field names and datatypes for the particular table
     *
     * @param string $tableName
     * @return array List of columns an an associative array with the keys Column and DataType
     */
    public function tableDetails($tableName)
    {
        $query = "SELECT a.attname as \"Column\", pg_catalog.format_type(a.atttypid, a.atttypmod) as \"Datatype\"
                FROM pg_catalog.pg_attribute a
                WHERE a.attnum > 0 AND NOT a.attisdropped AND a.attrelid = (
                    SELECT c.oid
                    FROM pg_catalog.pg_class c
                    LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
                    WHERE c.relname = ? AND pg_catalog.pg_table_is_visible(c.oid) AND n.nspname = ?
                );";

        $result = $this->preparedQuery(
            $query,
            array($tableName, $this->database->currentSchema())
        );

        $table = array();
        foreach ($result as $row) {
            $table[] = array(
                'Column' => $row['Column'],
                'DataType' => $row['DataType']
            );
        }

        return $table;
    }

    /**
     * Pass a legit trigger name and it will be dropped
     * This assumes that the trigger has been named in a unique fashion
     *
     * @param string $triggerName Name of the trigger
     * @param string $tableName Name of the table
     */
    protected function dropTrigger($triggerName, $tableName)
    {
        $exists = $this->preparedQuery(
            "
            SELECT trigger_name
            FROM information_schema.triggers
            WHERE trigger_name = ? AND trigger_schema = ?;",
            array($triggerName, $this->database->currentSchema())
        )->first();
        if ($exists) {
            $this->query("DROP trigger IF EXISTS $triggerName ON \"$tableName\";");
        }
    }

    /**
     * This will return the fields that the trigger is monitoring
     *
     * @param string $trigger Name of the trigger
     * @return array
     */
    protected function triggerFieldsFromTrigger($trigger)
    {
        if ($trigger) {
            $tsvector = 'tsvector_update_trigger';
            $ts_pos = strpos($trigger, $tsvector);
            $details = trim(substr($trigger, $ts_pos + strlen($tsvector)), '();');
            //Now split this into bits:
            $bits = explode(',', $details);

            $fields = $bits[2];

            $field_bits = explode(',', str_replace('"', '', $fields));
            $result = array();
            foreach ($field_bits as $field_bit) {
                $result[] = trim($field_bit);
            }

            return $result;
        } else {
            return false;
        }
    }

    /**
     * Return a boolean type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function boolean($values)
    {
        $default = $values['default'] ? '1' : '0';
        return "smallint default {$default}";
    }

    /**
     * Return a date type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function date($values)
    {
        return "date";
    }

    /**
     * Return a decimal type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function decimal($values)
    {
        // Avoid empty strings being put in the db
        if ($values['precision'] == '') {
            $precision = 1;
        } else {
            $precision = $values['precision'];
        }

        $defaultValue = '';
        if (isset($values['default']) && is_numeric($values['default'])) {
            $defaultValue = ' default ' . floatval($values['default']);
        }

        return "decimal($precision)$defaultValue";
    }

    /**
     * Return a enum type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function enum($values)
    {
        $default = " default '{$values['default']}'";
        return "varchar(255)" . $default . " check (\"" . $values['name'] . "\" in ('" . implode(
            '\', \'',
            $values['enums']
        ) . "', null))";
    }

    /**
     * Return a float type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function float($values)
    {
        return "float";
    }

    /**
     * Return a float type-formatted string cause double is not supported
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function double($values)
    {
        return $this->float($values);
    }

    /**
     * Return a int type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function int($values)
    {
        return "integer default " . (int)$values['default'];
    }

    /**
     * Return a bigint type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function bigint($values)
    {
        return "bigint default " . (int)$values['default'];
    }

    /**
     * Return a datetime type-formatted string
     * For PostgreSQL, we simply return the word 'timestamp', no other parameters are necessary
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function datetime($values)
    {
        return "timestamp";
    }

    /**
     * Return a text type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function text($values)
    {
        return "text";
    }

    /**
     * Return a time type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function time($values)
    {
        return "time";
    }

    /**
     * Return a varchar type-formatted string
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function varchar($values)
    {
        if (!isset($values['precision'])) {
            $values['precision'] = 255;
        }

        return "varchar({$values['precision']})";
    }

    /*
     * Return a 4 digit numeric type.  MySQL has a proprietary 'Year' type.
     * For Postgres, we'll use a 4 digit numeric
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function year($values)
    {
        return "decimal(4,0)";
    }

    /**
     * Create a fulltext search datatype for PostgreSQL
     * This will also return a trigger to be applied to this table
     *
     * @todo: create custom functions to allow weighted searches
     *
     * @param array $this_index Index specification for the fulltext index
     * @param string $tableName
     * @param string $name
     * @return array
     */
    protected function fulltext($this_index, $tableName, $name)
    {
        //For full text search, we need to create a column for the index
        $columns = $this->implodeColumnList($this_index['columns']);

        $fulltexts = "\"ts_$name\" tsvector";
        $triggerName = $this->buildPostgresTriggerName($tableName, $name);
        $language = PostgreSQLDatabase::search_language();

        $this->dropTrigger($triggerName, $tableName);
        $triggers = "CREATE TRIGGER \"$triggerName\" BEFORE INSERT OR UPDATE
                    ON \"$tableName\" FOR EACH ROW EXECUTE PROCEDURE
                    tsvector_update_trigger(\"ts_$name\", 'pg_catalog.$language', $columns);";

        return array(
            'name' => $name,
            'ts_name' => "ts_{$name}",
            'fulltexts' => $fulltexts,
            'triggers' => $triggers
        );
    }

    public function IdColumn($asDbValue = false, $hasAutoIncPK = true)
    {
        if ($asDbValue) {
            return 'bigint';
        } else {
            return 'serial8 not null';
        }
    }

    public function hasTable($tableName)
    {
        $result = $this->preparedQuery(
            "SELECT tablename FROM pg_catalog.pg_tables WHERE schemaname = ? AND tablename = ?;",
            array($this->database->currentSchema(), $tableName)
        );
        return ($result->numRecords() > 0);
    }

    /**
     * Returns the values of the given enum field
     *
     * @todo Make a proper implementation
     *
     * @param string $tableName Name of table to check
     * @param string $fieldName name of enum field to check
     * @return array List of enum values
     */
    public function enumValuesForField($tableName, $fieldName)
    {
        //return array('SiteTree','Page');
        $constraints = $this->constraintExists("{$tableName}_{$fieldName}_check");
        if ($constraints) {
            return $this->enumValuesFromConstraint($constraints['pg_get_constraintdef']);
        } else {
            return array();
        }
    }

    /**
     * Get the actual enum fields from the constraint value:
     *
     * @param string $constraint
     * @return array
     */
    protected function enumValuesFromConstraint($constraint)
    {
        $constraint = substr($constraint, strpos($constraint, 'ANY (ARRAY[') + 11);
        $constraint = substr($constraint, 0, -11);
        $constraints = array();
        $segments = explode(',', $constraint);
        foreach ($segments as $this_segment) {
            $bits = preg_split('/ *:: */', $this_segment);
            array_unshift($constraints, trim($bits[0], " '"));
        }
        return $constraints;
    }

    public function dbDataType($type)
    {
        $values = array(
            'unsigned integer' => 'INT'
        );

        if (isset($values[$type])) {
            return $values[$type];
        } else {
            return '';
        }
    }

    /*
     * Given a tablespace and and location, either create a new one
     * or update the existing one
     *
     * @param string $name
     * @param string $location
     */
    public function createOrReplaceTablespace($name, $location)
    {
        $existing = $this->preparedQuery(
            "SELECT spcname, spclocation FROM pg_tablespace WHERE spcname = ?;",
            array($name)
        )->first();

        //NOTE: this location must be empty for this to work
        //We can't seem to change the location of the tablespace through any ALTER commands :(

        //If a tablespace with this name exists, but the location has changed, then drop the current one
        //if($existing && $location!=$existing['spclocation'])
        //    DB::query("DROP TABLESPACE $name;");

        //If this is a new tablespace, or we have dropped the current one:
        if (!$existing || ($existing && $location != $existing['spclocation'])) {
            $this->query("CREATE TABLESPACE $name LOCATION '$location';");
        }
    }

    /**
     *
     * @param string $tableName
     * @param array $partitions
     * @param array $indexes
     * @param array $extensions
     */
    public function createOrReplacePartition($tableName, $partitions, $indexes = [], $extensions = [])
    {

        //We need the plpgsql language to be installed for this to work:
        $this->createLanguage('plpgsql');

        $trigger = 'CREATE OR REPLACE FUNCTION ' . $tableName . '_insert_trigger() RETURNS TRIGGER AS $$ BEGIN ';
        $first = true;

        //Do we need to create a tablespace for this item?
        if ($extensions && isset($extensions['tablespace'])) {
            $this->createOrReplaceTablespace($extensions['tablespace']['name'], $extensions['tablespace']['location']);
            $tableSpace = ' TABLESPACE ' . $extensions['tablespace']['name'];
        } else {
            $tableSpace = '';
        }

        foreach ($partitions as $partition_name => $partition_value) {
            //Check that this child table does not already exist:
            if (!$this->hasTable($partition_name)) {
                $this->query("CREATE TABLE \"$partition_name\" (CHECK (" . str_replace(
                    'NEW.',
                    '',
                    $partition_value
                ) . ")) INHERITS (\"$tableName\")$tableSpace;");
            } else {
                //Drop the constraint, we will recreate in in the next line
                $constraintName = "{$partition_name}_pkey";
                $constraintExists = $this->constraintExists($constraintName, false);
                if ($constraintExists) {
                    $this->query("ALTER TABLE \"$partition_name\" DROP CONSTRAINT \"{$constraintName}\";");
                }
                $this->dropTrigger(strtolower('trigger_' . $tableName . '_insert'), $tableName);
            }

            $this->query("ALTER TABLE \"$partition_name\" ADD CONSTRAINT \"{$partition_name}_pkey\" PRIMARY KEY (\"ID\");");

            if ($first) {
                $trigger .= 'IF';
                $first = false;
            } else {
                $trigger .= 'ELSIF';
            }

            $trigger .= " ($partition_value) THEN INSERT INTO \"$partition_name\" VALUES (NEW.*);";

            if ($indexes) {
                // We need to propogate the indexes through to the child pages.
                // Some of this code is duplicated, and could be tidied up
                foreach ($indexes as $name => $this_index) {
                    if ($this_index['type'] == 'fulltext') {
                        $fillfactor = $where = '';
                        if (isset($this_index['fillfactor'])) {
                            $fillfactor = 'WITH (FILLFACTOR = ' . $this_index['fillfactor'] . ')';
                        }
                        if (isset($this_index['where'])) {
                            $where = 'WHERE ' . $this_index['where'];
                        }
                        $clusterMethod = PostgreSQLDatabase::default_fts_cluster_method();
                        $this->query("CREATE INDEX \"" . $this->buildPostgresIndexName(
                            $partition_name,
                            $this_index['name']
                        ) . "\" ON \"" . $partition_name . "\" USING $clusterMethod(\"ts_" . $name . "\") $fillfactor $where");
                        $ts_details = $this->fulltext($this_index, $partition_name, $name);
                        $this->query($ts_details['triggers']);
                    } else {
                        if (is_array($this_index)) {
                            $index_name = $this_index['name'];
                        } else {
                            $index_name = trim($this_index, '()');
                        }

                        $createIndex = $this->getIndexSqlDefinition($partition_name, $index_name, $this_index);
                        if ($createIndex !== false) {
                            $this->query($createIndex);
                        }
                    }
                }
            }

            //Lastly, clustering goes here:
            if ($extensions && isset($extensions['cluster'])) {
                $this->query("CLUSTER \"$partition_name\" USING \"{$extensions['cluster']}\";");
            }
        }

        $trigger .= 'ELSE RAISE EXCEPTION \'Value id out of range.  Fix the ' . $tableName . '_insert_trigger() function!\'; END IF; RETURN NULL; END; $$ LANGUAGE plpgsql;';
        $trigger .= 'CREATE TRIGGER trigger_' . $tableName . '_insert BEFORE INSERT ON "' . $tableName . '" FOR EACH ROW EXECUTE PROCEDURE ' . $tableName . '_insert_trigger();';

        $this->query($trigger);
    }

    /*
     * This will create a language if it doesn't already exist.
     * This is used by the createOrReplacePartition function, which needs plpgsql
     *
     * @param string $language Language name
     */
    public function createLanguage($language)
    {
        $result = $this->preparedQuery(
            "SELECT lanname FROM pg_language WHERE lanname = ?;",
            array($language)
        )->first();

        if (!$result) {
            $this->query("CREATE LANGUAGE $language;");
        }
    }

    /**
     * Return a set type-formatted string
     * This is used for Multi-enum support, which isn't actually supported by Postgres.
     * Throws a user error to show our lack of support, and return an "int", specifically for sapphire
     * tests that test multi-enums. This results in a test failure, but not crashing the test run.
     *
     * @param array $values Contains a tokenised list of info about this data type
     * @return string
     */
    public function set($values)
    {
        user_error("PostGreSQL does not support multi-enum", E_USER_ERROR);
        return "int";
    }
}