db.py

from .utils import sqlite3, OperationalError, suggest_column_types, column_affinity
from collections import namedtuple, OrderedDict
import datetime
import decimal
import hashlib
import itertools
import json
import os
import pathlib

SQLITE_MAX_VARS = 999


try:
    import pandas as pd
except ImportError:
    pd = None

try:
    import numpy as np
except ImportError:
    np = None

Column = namedtuple(
    "Column", ("cid", "name", "type", "notnull", "default_value", "is_pk")
)
ForeignKey = namedtuple(
    "ForeignKey", ("table", "column", "other_table", "other_column")
)
Index = namedtuple("Index", ("seq", "name", "unique", "origin", "partial", "columns"))
Trigger = namedtuple("Trigger", ("name", "table", "sql"))


DEFAULT = object()

COLUMN_TYPE_MAPPING = {
    float: "FLOAT",
    int: "INTEGER",
    bool: "INTEGER",
    str: "TEXT",
    bytes.__class__: "BLOB",
    bytes: "BLOB",
    datetime.datetime: "TEXT",
    datetime.date: "TEXT",
    datetime.time: "TEXT",
    decimal.Decimal: "FLOAT",
    None.__class__: "TEXT",
    # SQLite explicit types
    "TEXT": "TEXT",
    "INTEGER": "INTEGER",
    "FLOAT": "FLOAT",
    "BLOB": "BLOB",
    "text": "TEXT",
    "integer": "INTEGER",
    "float": "FLOAT",
    "blob": "BLOB",
}
# If numpy is available, add more types
if np:
    COLUMN_TYPE_MAPPING.update(
        {
            np.int8: "INTEGER",
            np.int16: "INTEGER",
            np.int32: "INTEGER",
            np.int64: "INTEGER",
            np.uint8: "INTEGER",
            np.uint16: "INTEGER",
            np.uint32: "INTEGER",
            np.uint64: "INTEGER",
            np.float16: "FLOAT",
            np.float32: "FLOAT",
            np.float64: "FLOAT",
        }
    )

# If pandas is available, add more types
if pd:
    COLUMN_TYPE_MAPPING.update({pd.Timestamp: "TEXT"})


class AlterError(Exception):
    pass


class NoObviousTable(Exception):
    pass


class BadPrimaryKey(Exception):
    pass


class NotFoundError(Exception):
    pass


class PrimaryKeyRequired(Exception):
    pass


class Database:
    def __init__(self, filename_or_conn=None, memory=False, recreate=False):
        assert (filename_or_conn is not None and not memory) or (
            filename_or_conn is None and memory
        ), "Either specify a filename_or_conn or pass memory=True"
        if memory or filename_or_conn == ":memory:":
            self.conn = sqlite3.connect(":memory:")
        elif isinstance(filename_or_conn, (str, pathlib.Path)):
            if recreate and os.path.exists(filename_or_conn):
                os.remove(filename_or_conn)
            self.conn = sqlite3.connect(str(filename_or_conn))
        else:
            assert not recreate, "recreate cannot be used with connections, only paths"
            self.conn = filename_or_conn

    def __getitem__(self, table_name):
        return self.table(table_name)

    def __repr__(self):
        return "<Database {}>".format(self.conn)

    def table(self, table_name, **kwargs):
        klass = View if table_name in self.view_names() else Table
        return klass(self, table_name, **kwargs)

    def escape(self, value):
        # Normally we would use .execute(sql, [params]) for escaping, but
        # occasionally that isn't available - most notable when we need
        # to include a "... DEFAULT 'value'" in a column definition.
        return self.conn.execute(
            # Use SQLite itself to correctly escape this string:
            "SELECT quote(:value)",
            {"value": value},
        ).fetchone()[0]

    def table_names(self, fts4=False, fts5=False):
        where = ["type = 'table'"]
        if fts4:
            where.append("sql like '%FTS4%'")
        if fts5:
            where.append("sql like '%FTS5%'")
        sql = "select name from sqlite_master where {}".format(" AND ".join(where))
        return [r[0] for r in self.conn.execute(sql).fetchall()]

    def view_names(self):
        return [
            r[0]
            for r in self.conn.execute(
                "select name from sqlite_master where type = 'view'"
            ).fetchall()
        ]

    @property
    def tables(self):
        return [self[name] for name in self.table_names()]

    @property
    def views(self):
        return [self[name] for name in self.view_names()]

    @property
    def triggers(self):
        return [
            Trigger(*r)
            for r in self.conn.execute(
                "select name, tbl_name, sql from sqlite_master where type = 'trigger'"
            ).fetchall()
        ]

    def execute_returning_dicts(self, sql, params=None):
        cursor = self.conn.execute(sql, params or tuple())
        keys = [d[0] for d in cursor.description]
        return [dict(zip(keys, row)) for row in cursor.fetchall()]

    def resolve_foreign_keys(self, name, foreign_keys):
        # foreign_keys may be a list of strcolumn names, a list of ForeignKey tuples,
        # a list of tuple-pairs or a list of tuple-triples. We want to turn
        # it into a list of ForeignKey tuples
        if all(isinstance(fk, ForeignKey) for fk in foreign_keys):
            return foreign_keys
        if all(isinstance(fk, str) for fk in foreign_keys):
            # It's a list of columns
            fks = []
            for column in foreign_keys:
                other_table = self[name].guess_foreign_table(column)
                other_column = self[name].guess_foreign_column(other_table)
                fks.append(ForeignKey(name, column, other_table, other_column))
            return fks
        assert all(
            isinstance(fk, (tuple, list)) for fk in foreign_keys
        ), "foreign_keys= should be a list of tuples"
        fks = []
        for tuple_or_list in foreign_keys:
            assert len(tuple_or_list) in (
                2,
                3,
            ), "foreign_keys= should be a list of tuple pairs or triples"
            if len(tuple_or_list) == 3:
                fks.append(
                    ForeignKey(
                        name, tuple_or_list[0], tuple_or_list[1], tuple_or_list[2]
                    )
                )
            else:
                # Guess the primary key
                fks.append(
                    ForeignKey(
                        name,
                        tuple_or_list[0],
                        tuple_or_list[1],
                        self[name].guess_foreign_column(tuple_or_list[1]),
                    )
                )
        return fks

    def create_table(
        self,
        name,
        columns,
        pk=None,
        foreign_keys=None,
        column_order=None,
        not_null=None,
        defaults=None,
        hash_id=None,
        extracts=None,
    ):
        foreign_keys = self.resolve_foreign_keys(name, foreign_keys or [])
        foreign_keys_by_column = {fk.column: fk for fk in foreign_keys}
        # any extracts will be treated as integer columns with a foreign key
        extracts = resolve_extracts(extracts)
        for extract_column, extract_table in extracts.items():
            # Ensure other table exists
            if not self[extract_table].exists():
                self.create_table(extract_table, {"id": int, "value": str}, pk="id")
            columns[extract_column] = int
            foreign_keys_by_column[extract_column] = ForeignKey(
                name, extract_column, extract_table, "id"
            )
        # Sanity check not_null, and defaults if provided
        not_null = not_null or set()
        defaults = defaults or {}
        assert all(
            n in columns for n in not_null
        ), "not_null set {} includes items not in columns {}".format(
            repr(not_null), repr(set(columns.keys()))
        )
        assert all(
            n in columns for n in defaults
        ), "defaults set {} includes items not in columns {}".format(
            repr(set(defaults)), repr(set(columns.keys()))
        )
        validate_column_names(columns.keys())
        column_items = list(columns.items())
        if column_order is not None:
            column_items.sort(
                key=lambda p: column_order.index(p[0]) if p[0] in column_order else 999
            )
        if hash_id:
            column_items.insert(0, (hash_id, str))
            pk = hash_id
        # Sanity check foreign_keys point to existing tables
        for fk in foreign_keys:
            if not any(
                c for c in self[fk.other_table].columns if c.name == fk.other_column
            ):
                raise AlterError(
                    "No such column: {}.{}".format(fk.other_table, fk.other_column)
                )

        column_defs = []
        # ensure pk is a tuple
        single_pk = None
        if isinstance(pk, str):
            single_pk = pk
            if pk not in [c[0] for c in column_items]:
                column_items.insert(0, (pk, int))
        for column_name, column_type in column_items:
            column_extras = []
            if column_name == single_pk:
                column_extras.append("PRIMARY KEY")
            if column_name in not_null:
                column_extras.append("NOT NULL")
            if column_name in defaults:
                column_extras.append(
                    "DEFAULT {}".format(self.escape(defaults[column_name]))
                )
            if column_name in foreign_keys_by_column:
                column_extras.append(
                    "REFERENCES [{other_table}]([{other_column}])".format(
                        other_table=foreign_keys_by_column[column_name].other_table,
                        other_column=foreign_keys_by_column[column_name].other_column,
                    )
                )
            column_defs.append(
                "   [{column_name}] {column_type}{column_extras}".format(
                    column_name=column_name,
                    column_type=COLUMN_TYPE_MAPPING[column_type],
                    column_extras=(" " + " ".join(column_extras))
                    if column_extras
                    else "",
                )
            )
        extra_pk = ""
        if single_pk is None and pk and len(pk) > 1:
            extra_pk = ",\n   PRIMARY KEY ({pks})".format(
                pks=", ".join(["[{}]".format(p) for p in pk])
            )
        columns_sql = ",\n".join(column_defs)
        sql = """CREATE TABLE [{table}] (
{columns_sql}{extra_pk}
);
        """.format(
            table=name, columns_sql=columns_sql, extra_pk=extra_pk
        )
        self.conn.execute(sql)
        return self.table(
            name,
            pk=pk,
            foreign_keys=foreign_keys,
            column_order=column_order,
            not_null=not_null,
            defaults=defaults,
            hash_id=hash_id,
        )

    def create_view(self, name, sql, ignore=False, replace=False):
        assert not (
            ignore and replace
        ), "Use one or the other of ignore/replace, not both"
        create_sql = "CREATE VIEW {name} AS {sql}".format(name=name, sql=sql)
        if ignore or replace:
            # Does view exist already?
            if name in self.view_names():
                if ignore:
                    return self
                elif replace:
                    # If SQL is the same, do nothing
                    if create_sql == self[name].schema:
                        return self
                    self[name].drop()
        self.conn.execute(create_sql)
        return self

    def m2m_table_candidates(self, table, other_table):
        "Returns potential m2m tables for arguments, based on FKs"
        candidates = []
        tables = {table, other_table}
        for table in self.tables:
            # Does it have foreign keys to both table and other_table?
            has_fks_to = {fk.other_table for fk in table.foreign_keys}
            if has_fks_to.issuperset(tables):
                candidates.append(table.name)
        return candidates

    def add_foreign_keys(self, foreign_keys):
        # foreign_keys is a list of explicit 4-tuples
        assert all(
            len(fk) == 4 and isinstance(fk, (list, tuple)) for fk in foreign_keys
        ), "foreign_keys must be a list of 4-tuples, (table, column, other_table, other_column)"

        foreign_keys_to_create = []

        # Verify that all tables and columns exist
        for table, column, other_table, other_column in foreign_keys:
            if not self[table].exists():
                raise AlterError("No such table: {}".format(table))
            if column not in self[table].columns_dict:
                raise AlterError("No such column: {} in {}".format(column, table))
            if not self[other_table].exists():
                raise AlterError("No such other_table: {}".format(other_table))
            if (
                other_column != "rowid"
                and other_column not in self[other_table].columns_dict
            ):
                raise AlterError(
                    "No such other_column: {} in {}".format(other_column, other_table)
                )
            # We will silently skip foreign keys that exist already
            if not any(
                fk
                for fk in self[table].foreign_keys
                if fk.column == column
                and fk.other_table == other_table
                and fk.other_column == other_column
            ):
                foreign_keys_to_create.append(
                    (table, column, other_table, other_column)
                )

        # Construct SQL for use with "UPDATE sqlite_master SET sql = ? WHERE name = ?"
        table_sql = {}
        for table, column, other_table, other_column in foreign_keys_to_create:
            old_sql = table_sql.get(table, self[table].schema)
            extra_sql = ",\n   FOREIGN KEY({column}) REFERENCES {other_table}({other_column})\n".format(
                column=column, other_table=other_table, other_column=other_column
            )
            # Stick that bit in at the very end just before the closing ')'
            last_paren = old_sql.rindex(")")
            new_sql = old_sql[:last_paren].strip() + extra_sql + old_sql[last_paren:]
            table_sql[table] = new_sql

        # And execute it all within a single transaction
        with self.conn:
            cursor = self.conn.cursor()
            schema_version = cursor.execute("PRAGMA schema_version").fetchone()[0]
            cursor.execute("PRAGMA writable_schema = 1")
            for table_name, new_sql in table_sql.items():
                cursor.execute(
                    "UPDATE sqlite_master SET sql = ? WHERE name = ?",
                    (new_sql, table_name),
                )
            cursor.execute("PRAGMA schema_version = %d" % (schema_version + 1))
            cursor.execute("PRAGMA writable_schema = 0")
        # Have to VACUUM outside the transaction to ensure .foreign_keys property
        # can see the newly created foreign key.
        self.vacuum()

    def index_foreign_keys(self):
        for table_name in self.table_names():
            table = self[table_name]
            existing_indexes = {
                i.columns[0] for i in table.indexes if len(i.columns) == 1
            }
            for fk in table.foreign_keys:
                if fk.column not in existing_indexes:
                    table.create_index([fk.column])

    def vacuum(self):
        self.conn.execute("VACUUM;")


class Queryable:
    def exists(self):
        return False

    def __init__(self, db, name):
        self.db = db
        self.name = name

    @property
    def count(self):
        return self.db.conn.execute(
            "select count(*) from [{}]".format(self.name)
        ).fetchone()[0]

    @property
    def rows(self):
        return self.rows_where()

    def rows_where(self, where=None, where_args=None, order_by=None):
        if not self.exists():
            return []
        sql = "select * from [{}]".format(self.name)
        if where is not None:
            sql += " where " + where
        if order_by is not None:
            sql += " order by " + order_by
        cursor = self.db.conn.execute(sql, where_args or [])
        columns = [c[0] for c in cursor.description]
        for row in cursor:
            yield dict(zip(columns, row))

    @property
    def columns(self):
        if not self.exists():
            return []
        rows = self.db.conn.execute(
            "PRAGMA table_info([{}])".format(self.name)
        ).fetchall()
        return [Column(*row) for row in rows]

    @property
    def columns_dict(self):
        "Returns {column: python-type} dictionary"
        return {column.name: column_affinity(column.type) for column in self.columns}

    @property
    def schema(self):
        return self.db.conn.execute(
            "select sql from sqlite_master where name = ?", (self.name,)
        ).fetchone()[0]


class Table(Queryable):
    last_rowid = None
    last_pk = None

    def __init__(
        self,
        db,
        name,
        pk=None,
        foreign_keys=None,
        column_order=None,
        not_null=None,
        defaults=None,
        batch_size=100,
        hash_id=None,
        alter=False,
        ignore=False,
        replace=False,
        extracts=None,
        conversions=None,
        columns=None,
    ):
        super().__init__(db, name)
        self._defaults = dict(
            pk=pk,
            foreign_keys=foreign_keys,
            column_order=column_order,
            not_null=not_null,
            defaults=defaults,
            batch_size=batch_size,
            hash_id=hash_id,
            alter=alter,
            ignore=ignore,
            replace=replace,
            extracts=extracts,
            conversions=conversions or {},
            columns=columns,
        )

    def __repr__(self):
        return "<Table {}{}>".format(
            self.name,
            " (does not exist yet)"
            if not self.exists()
            else " ({})".format(", ".join(c.name for c in self.columns)),
        )

    def exists(self):
        return self.name in self.db.table_names()

    @property
    def pks(self):
        names = [column.name for column in self.columns if column.is_pk]
        if not names:
            names = ["rowid"]
        return names

    def get(self, pk_values):
        if not isinstance(pk_values, (list, tuple)):
            pk_values = [pk_values]
        pks = self.pks
        last_pk = pk_values[0] if len(pks) == 1 else pk_values
        if len(pks) != len(pk_values):
            raise NotFoundError(
                "Need {} primary key value{}".format(
                    len(pks), "" if len(pks) == 1 else "s"
                )
            )

        wheres = ["[{}] = ?".format(pk_name) for pk_name in pks]
        rows = self.rows_where(" and ".join(wheres), pk_values)
        try:
            row = list(rows)[0]
            self.last_pk = last_pk
            return row
        except IndexError:
            raise NotFoundError

    @property
    def foreign_keys(self):
        fks = []
        for row in self.db.conn.execute(
            "PRAGMA foreign_key_list([{}])".format(self.name)
        ).fetchall():
            if row is not None:
                id, seq, table_name, from_, to_, on_update, on_delete, match = row
                fks.append(
                    ForeignKey(
                        table=self.name,
                        column=from_,
                        other_table=table_name,
                        other_column=to_,
                    )
                )
        return fks

    @property
    def indexes(self):
        sql = 'PRAGMA index_list("{}")'.format(self.name)
        indexes = []
        for row in self.db.execute_returning_dicts(sql):
            index_name = row["name"]
            index_name_quoted = (
                '"{}"'.format(index_name)
                if not index_name.startswith('"')
                else index_name
            )
            column_sql = "PRAGMA index_info({})".format(index_name_quoted)
            columns = []
            for seqno, cid, name in self.db.conn.execute(column_sql).fetchall():
                columns.append(name)
            row["columns"] = columns
            # These columns may be missing on older SQLite versions:
            for key, default in {"origin": "c", "partial": 0}.items():
                if key not in row:
                    row[key] = default
            indexes.append(Index(**row))
        return indexes

    @property
    def triggers(self):
        return [
            Trigger(*r)
            for r in self.db.conn.execute(
                "select name, tbl_name, sql from sqlite_master where type = 'trigger'"
                " and tbl_name = ?",
                (self.name,),
            ).fetchall()
        ]

    def create(
        self,
        columns,
        pk=None,
        foreign_keys=None,
        column_order=None,
        not_null=None,
        defaults=None,
        hash_id=None,
        extracts=None,
    ):
        columns = {name: value for (name, value) in columns.items()}
        with self.db.conn:
            self.db.create_table(
                self.name,
                columns,
                pk=pk,
                foreign_keys=foreign_keys,
                column_order=column_order,
                not_null=not_null,
                defaults=defaults,
                hash_id=hash_id,
                extracts=extracts,
            )
        return self

    def create_index(self, columns, index_name=None, unique=False, if_not_exists=False):
        if index_name is None:
            index_name = "idx_{}_{}".format(
                self.name.replace(" ", "_"), "_".join(columns)
            )
        sql = """
            CREATE {unique}INDEX {if_not_exists}[{index_name}]
                ON [{table_name}] ({columns});
        """.format(
            index_name=index_name,
            table_name=self.name,
            columns=", ".join("[{}]".format(c) for c in columns),
            unique="UNIQUE " if unique else "",
            if_not_exists="IF NOT EXISTS " if if_not_exists else "",
        )
        self.db.conn.execute(sql)
        return self

    def add_column(
        self, col_name, col_type=None, fk=None, fk_col=None, not_null_default=None
    ):
        fk_col_type = None
        if fk is not None:
            # fk must be a valid table
            if not fk in self.db.table_names():
                raise AlterError("table '{}' does not exist".format(fk))
            # if fk_col specified, must be a valid column
            if fk_col is not None:
                if fk_col not in self.db[fk].columns_dict:
                    raise AlterError("table '{}' has no column {}".format(fk, fk_col))
            else:
                # automatically set fk_col to first primary_key of fk table
                pks = [c for c in self.db[fk].columns if c.is_pk]
                if pks:
                    fk_col = pks[0].name
                    fk_col_type = pks[0].type
                else:
                    fk_col = "rowid"
                    fk_col_type = "INTEGER"
        if col_type is None:
            col_type = str
        not_null_sql = None
        if not_null_default is not None:
            not_null_sql = "NOT NULL DEFAULT {}".format(
                self.db.escape(not_null_default)
            )
        sql = "ALTER TABLE [{table}] ADD COLUMN [{col_name}] {col_type}{not_null_default};".format(
            table=self.name,
            col_name=col_name,
            col_type=fk_col_type or COLUMN_TYPE_MAPPING[col_type],
            not_null_default=(" " + not_null_sql) if not_null_sql else "",
        )
        self.db.conn.execute(sql)
        if fk is not None:
            self.add_foreign_key(col_name, fk, fk_col)
        return self

    def drop(self):
        self.db.conn.execute("DROP TABLE [{}]".format(self.name))

    def guess_foreign_table(self, column):
        column = column.lower()
        possibilities = [column]
        if column.endswith("_id"):
            column_without_id = column[:-3]
            possibilities.append(column_without_id)
            if not column_without_id.endswith("s"):
                possibilities.append(column_without_id + "s")
        elif not column.endswith("s"):
            possibilities.append(column + "s")
        existing_tables = {t.lower(): t for t in self.db.table_names()}
        for table in possibilities:
            if table in existing_tables:
                return existing_tables[table]
        # If we get here there's no obvious candidate - raise an error
        raise NoObviousTable(
            "No obvious foreign key table for column '{}' - tried {}".format(
                column, repr(possibilities)
            )
        )

    def guess_foreign_column(self, other_table):
        pks = [c for c in self.db[other_table].columns if c.is_pk]
        if len(pks) != 1:
            raise BadPrimaryKey(
                "Could not detect single primary key for table '{}'".format(other_table)
            )
        else:
            return pks[0].name

    def add_foreign_key(self, column, other_table=None, other_column=None):
        # Ensure column exists
        if column not in self.columns_dict:
            raise AlterError("No such column: {}".format(column))
        # If other_table is not specified, attempt to guess it from the column
        if other_table is None:
            other_table = self.guess_foreign_table(column)
        # If other_column is not specified, detect the primary key on other_table
        if other_column is None:
            other_column = self.guess_foreign_column(other_table)

        # Sanity check that the other column exists
        if (
            not [c for c in self.db[other_table].columns if c.name == other_column]
            and other_column != "rowid"
        ):
            raise AlterError("No such column: {}.{}".format(other_table, other_column))
        # Check we do not already have an existing foreign key
        if any(
            fk
            for fk in self.foreign_keys
            if fk.column == column
            and fk.other_table == other_table
            and fk.other_column == other_column
        ):
            raise AlterError(
                "Foreign key already exists for {} => {}.{}".format(
                    column, other_table, other_column
                )
            )
        self.db.add_foreign_keys([(self.name, column, other_table, other_column)])

    def enable_fts(self, columns, fts_version="FTS5", create_triggers=False):
        "Enables FTS on the specified columns."
        sql = """
            CREATE VIRTUAL TABLE [{table}_fts] USING {fts_version} (
                {columns},
                content=[{table}]
            );
        """.format(
            table=self.name,
            columns=", ".join("[{}]".format(c) for c in columns),
            fts_version=fts_version,
        )
        self.db.conn.executescript(sql)
        self.populate_fts(columns)

        if create_triggers:
            old_cols = ", ".join("old.[{}]".format(c) for c in columns)
            new_cols = ", ".join("new.[{}]".format(c) for c in columns)
            triggers = """
                CREATE TRIGGER [{table}_ai] AFTER INSERT ON [{table}] BEGIN
                  INSERT INTO [{table}_fts] (rowid, {columns}) VALUES (new.rowid, {new_cols});
                END;
                CREATE TRIGGER [{table}_ad] AFTER DELETE ON [{table}] BEGIN
                  INSERT INTO [{table}_fts] ([{table}_fts], rowid, {columns}) VALUES('delete', old.rowid, {old_cols});
                END;
                CREATE TRIGGER [{table}_au] AFTER UPDATE ON [{table}] BEGIN
                  INSERT INTO [{table}_fts] ([{table}_fts], rowid, {columns}) VALUES('delete', old.rowid, {old_cols});
                  INSERT INTO [{table}_fts] (rowid, {columns}) VALUES (new.rowid, {new_cols});
                END;
            """.format(
                table=self.name,
                columns=", ".join("[{}]".format(c) for c in columns),
                old_cols=old_cols,
                new_cols=new_cols,
            )
            self.db.conn.executescript(triggers)
        return self

    def populate_fts(self, columns):
        sql = """
            INSERT INTO [{table}_fts] (rowid, {columns})
                SELECT rowid, {columns} FROM [{table}];
        """.format(
            table=self.name, columns=", ".join("[{}]".format(c) for c in columns)
        )
        self.db.conn.executescript(sql)
        return self

    def disable_fts(self):
        fts_table = self.detect_fts()
        if fts_table:
            self.db[fts_table].drop()
        # Now delete the triggers that related to that table
        sql = """
            SELECT name FROM sqlite_master
                WHERE type = 'trigger'
                AND sql LIKE '% INSERT INTO [{}]%'
        """.format(
            fts_table
        )
        trigger_names = []
        for row in self.db.conn.execute(sql).fetchall():
            trigger_names.append(row[0])
        with self.db.conn:
            for trigger_name in trigger_names:
                self.db.conn.execute("DROP TRIGGER IF EXISTS [{}]".format(trigger_name))

    def detect_fts(self):
        "Detect if table has a corresponding FTS virtual table and return it"
        sql = """
            SELECT name FROM sqlite_master
                WHERE rootpage = 0
                AND (
                    sql LIKE '%VIRTUAL TABLE%USING FTS%content=%{table}%'
                    OR (
                        tbl_name = "{table}"
                        AND sql LIKE '%VIRTUAL TABLE%USING FTS%'
                    )
                )
        """.format(
            table=self.name
        )
        rows = self.db.conn.execute(sql).fetchall()
        if len(rows) == 0:
            return None
        else:
            return rows[0][0]

    def optimize(self):
        fts_table = self.detect_fts()
        if fts_table is not None:
            self.db.conn.execute(
                """
                INSERT INTO [{table}] ([{table}]) VALUES ("optimize");
            """.format(
                    table=fts_table
                )
            )
        return self

    def search(self, q):
        sql = """
            select * from "{table}" where rowid in (
                select rowid from [{table}_fts]
                where [{table}_fts] match :search
            )
            order by rowid
        """.format(
            table=self.name
        )
        return self.db.conn.execute(sql, (q,)).fetchall()

    def value_or_default(self, key, value):
        return self._defaults[key] if value is DEFAULT else value

    def delete(self, pk_values):
        if not isinstance(pk_values, (list, tuple)):
            pk_values = [pk_values]
        self.get(pk_values)
        wheres = ["[{}] = ?".format(pk_name) for pk_name in self.pks]
        sql = "delete from [{table}] where {wheres}".format(
            table=self.name, wheres=" and ".join(wheres)
        )
        with self.db.conn:
            self.db.conn.execute(sql, pk_values)

    def delete_where(self, where=None, where_args=None):
        if not self.exists():
            return []
        sql = "delete from [{}]".format(self.name)
        if where is not None:
            sql += " where " + where
        self.db.conn.execute(sql, where_args or [])

    def update(self, pk_values, updates=None, alter=False, conversions=None):
        updates = updates or {}
        conversions = conversions or {}
        if not isinstance(pk_values, (list, tuple)):
            pk_values = [pk_values]
        # Sanity check that the record exists (raises error if not):
        self.get(pk_values)
        if not updates:
            return self
        args = []
        sets = []
        wheres = []
        validate_column_names(updates.keys())
        for key, value in updates.items():
            sets.append("[{}] = {}".format(key, conversions.get(key, "?")))
            args.append(value)
        wheres = ["[{}] = ?".format(pk_name) for pk_name in self.pks]
        args.extend(pk_values)
        sql = "update [{table}] set {sets} where {wheres}".format(
            table=self.name, sets=", ".join(sets), wheres=" and ".join(wheres)
        )
        with self.db.conn:
            try:
                rowcount = self.db.conn.execute(sql, args).rowcount
            except OperationalError as e:
                if alter and (" column" in e.args[0]):
                    # Attempt to add any missing columns, then try again
                    self.add_missing_columns([updates])
                    rowcount = self.db.conn.execute(sql, args).rowcount
                else:
                    raise

            # TODO: Test this works (rolls back) - use better exception:
            assert rowcount == 1
        self.last_pk = pk_values[0] if len(self.pks) == 1 else pk_values
        return self

    def insert(
        self,
        record,
        pk=DEFAULT,
        foreign_keys=DEFAULT,
        column_order=DEFAULT,
        not_null=DEFAULT,
        defaults=DEFAULT,
        hash_id=DEFAULT,
        alter=DEFAULT,
        ignore=DEFAULT,
        replace=DEFAULT,
        extracts=DEFAULT,
        conversions=DEFAULT,
        columns=DEFAULT,
    ):
        return self.insert_all(
            [record],
            pk=pk,
            foreign_keys=foreign_keys,
            column_order=column_order,
            not_null=not_null,
            defaults=defaults,
            hash_id=hash_id,
            alter=alter,
            ignore=ignore,
            replace=replace,
            extracts=extracts,
            conversions=conversions,
            columns=columns,
        )

    def insert_all(
        self,
        records,
        pk=DEFAULT,
        foreign_keys=DEFAULT,
        column_order=DEFAULT,
        not_null=DEFAULT,
        defaults=DEFAULT,
        batch_size=DEFAULT,
        hash_id=DEFAULT,
        alter=DEFAULT,
        ignore=DEFAULT,
        replace=DEFAULT,
        extracts=DEFAULT,
        conversions=DEFAULT,
        columns=DEFAULT,
        upsert=False,
    ):
        """
        Like .insert() but takes a list of records and ensures that the table
        that it creates (if table does not exist) has columns for ALL of that
        data
        """
        pk = self.value_or_default("pk", pk)
        foreign_keys = self.value_or_default("foreign_keys", foreign_keys)
        column_order = self.value_or_default("column_order", column_order)
        not_null = self.value_or_default("not_null", not_null)
        defaults = self.value_or_default("defaults", defaults)
        batch_size = self.value_or_default("batch_size", batch_size)
        hash_id = self.value_or_default("hash_id", hash_id)
        alter = self.value_or_default("alter", alter)
        ignore = self.value_or_default("ignore", ignore)
        replace = self.value_or_default("replace", replace)
        extracts = self.value_or_default("extracts", extracts)
        conversions = self.value_or_default("conversions", conversions)
        columns = self.value_or_default("columns", columns)

        if upsert and (not pk and not hash_id):
            raise PrimaryKeyRequired("upsert() requires a pk")
        assert not (hash_id and pk), "Use either pk= or hash_id="
        if hash_id:
            pk = hash_id

        assert not (
            ignore and replace
        ), "Use either ignore=True or replace=True, not both"
        all_columns = None
        first = True
        num_records_processed = 0
        # We can only handle a max of 999 variables in a SQL insert, so
        # we need to adjust the batch_size down if we have too many cols
        records = iter(records)
        # Peek at first record to count its columns:
        try:
            first_record = next(records)
        except StopIteration:
            return self  # It was an empty list
        num_columns = len(first_record.keys())
        assert (
            num_columns <= SQLITE_MAX_VARS
        ), "Rows can have a maximum of {} columns".format(SQLITE_MAX_VARS)
        batch_size = max(1, min(batch_size, SQLITE_MAX_VARS // num_columns))
        self.last_rowid = None
        self.last_pk = None
        for chunk in chunks(itertools.chain([first_record], records), batch_size):
            chunk = list(chunk)
            num_records_processed += len(chunk)
            if first:
                if not self.exists():
                    # Use the first batch to derive the table names
                    column_types = suggest_column_types(chunk)
                    column_types.update(columns or {})
                    self.create(
                        column_types,
                        pk,
                        foreign_keys,
                        column_order=column_order,
                        not_null=not_null,
                        defaults=defaults,
                        hash_id=hash_id,
                        extracts=extracts,
                    )
                all_columns = set()
                for record in chunk:
                    all_columns.update(record.keys())
                all_columns = list(sorted(all_columns))
                if hash_id:
                    all_columns.insert(0, hash_id)
            validate_column_names(all_columns)
            first = False
            # values is the list of insert data that is passed to the
            # .execute() method - but some of them may be replaced by
            # new primary keys if we are extracting any columns.
            values = []
            extracts = resolve_extracts(extracts)
            for record in chunk:
                record_values = []
                for key in all_columns:
                    value = jsonify_if_needed(
                        record.get(key, None if key != hash_id else _hash(record))
                    )
                    if key in extracts:
                        extract_table = extracts[key]
                        value = self.db[extract_table].lookup({"value": value})
                    record_values.append(value)
                values.append(record_values)

            queries_and_params = []
            if upsert:
                if isinstance(pk, str):
                    pks = [pk]
                else:
                    pks = pk
                self.last_pk = None
                for record_values in values:
                    # TODO: make more efficient:
                    record = dict(zip(all_columns, record_values))
                    params = []
                    sql = "INSERT OR IGNORE INTO [{table}]({pks}) VALUES({pk_placeholders});".format(
                        table=self.name,
                        pks=", ".join(["[{}]".format(p) for p in pks]),
                        pk_placeholders=", ".join(["?" for p in pks]),
                    )
                    queries_and_params.append((sql, [record[col] for col in pks]))
                    # UPDATE [book] SET [name] = 'Programming' WHERE [id] = 1001;
                    set_cols = [col for col in all_columns if col not in pks]
                    sql2 = "UPDATE [{table}] SET {pairs} WHERE {wheres}".format(
                        table=self.name,
                        pairs=", ".join(
                            "[{}] = {}".format(col, conversions.get(col, "?"))
                            for col in set_cols
                        ),
                        wheres=" AND ".join("[{}] = ?".format(pk) for pk in pks),
                    )
                    queries_and_params.append(
                        (
                            sql2,
                            [record[col] for col in set_cols]
                            + [record[pk] for pk in pks],
                        )
                    )
                    # We can populate .last_pk right here
                    if num_records_processed == 1:
                        self.last_pk = tuple(record[pk] for pk in pks)
                        if len(self.last_pk) == 1:
                            self.last_pk = self.last_pk[0]

            else:
                or_what = ""
                if replace:
                    or_what = "OR REPLACE "
                elif ignore:
                    or_what = "OR IGNORE "
                sql = """
                    INSERT {or_what}INTO [{table}] ({columns}) VALUES {rows};
                """.format(
                    or_what=or_what,
                    table=self.name,
                    columns=", ".join("[{}]".format(c) for c in all_columns),
                    rows=", ".join(
                        """
                        ({placeholders})
                    """.format(
                            placeholders=", ".join(
                                [conversions.get(col, "?") for col in all_columns]
                            )
                        )
                        for record in chunk
                    ),
                )
                flat_values = list(itertools.chain(*values))
                queries_and_params = [(sql, flat_values)]

            with self.db.conn:
                for query, params in queries_and_params:
                    try:
                        result = self.db.conn.execute(query, params)
                    except OperationalError as e:
                        if alter and (" column" in e.args[0]):
                            # Attempt to add any missing columns, then try again
                            self.add_missing_columns(chunk)
                            result = self.db.conn.execute(query, params)
                        else:
                            raise
                if num_records_processed == 1 and not upsert:
                    self.last_rowid = result.lastrowid
                    self.last_pk = self.last_rowid
                    # self.last_rowid will be 0 if a "INSERT OR IGNORE" happened
                    if (hash_id or pk) and self.last_rowid:
                        row = list(self.rows_where("rowid = ?", [self.last_rowid]))[0]
                        if hash_id:
                            self.last_pk = row[hash_id]
                        elif isinstance(pk, str):
                            self.last_pk = row[pk]
                        else:
                            self.last_pk = tuple(row[p] for p in pk)
        return self

    def upsert(
        self,
        record,
        pk=DEFAULT,
        foreign_keys=DEFAULT,
        column_order=DEFAULT,
        not_null=DEFAULT,
        defaults=DEFAULT,
        hash_id=DEFAULT,
        alter=DEFAULT,
        extracts=DEFAULT,
        conversions=DEFAULT,
        columns=DEFAULT,
    ):
        return self.upsert_all(
            [record],
            pk=pk,
            foreign_keys=foreign_keys,
            column_order=column_order,
            not_null=not_null,
            defaults=defaults,
            hash_id=hash_id,
            alter=alter,
            extracts=extracts,
            conversions=conversions,
            columns=columns,
        )

    def upsert_all(
        self,
        records,
        pk=DEFAULT,
        foreign_keys=DEFAULT,
        column_order=DEFAULT,
        not_null=DEFAULT,
        defaults=DEFAULT,
        batch_size=DEFAULT,
        hash_id=DEFAULT,
        alter=DEFAULT,
        extracts=DEFAULT,
        conversions=DEFAULT,
        columns=DEFAULT,
    ):
        return self.insert_all(
            records,
            pk=pk,
            foreign_keys=foreign_keys,
            column_order=column_order,
            not_null=not_null,
            defaults=defaults,
            batch_size=batch_size,
            hash_id=hash_id,
            alter=alter,
            extracts=extracts,
            conversions=conversions,
            columns=columns,
            upsert=True,
        )

    def add_missing_columns(self, records):
        needed_columns = suggest_column_types(records)
        current_columns = self.columns_dict
        for col_name, col_type in needed_columns.items():
            if col_name not in current_columns:
                self.add_column(col_name, col_type)

    def lookup(self, column_values):
        # lookups is a dictionary - all columns will be used for a unique index
        assert isinstance(column_values, dict)
        if self.exists():
            self.add_missing_columns([column_values])
            unique_column_sets = [set(i.columns) for i in self.indexes]
            if set(column_values.keys()) not in unique_column_sets:
                self.create_index(column_values.keys(), unique=True)
            wheres = ["[{}] = ?".format(column) for column in column_values]
            rows = list(
                self.rows_where(
                    " and ".join(wheres), [value for _, value in column_values.items()]
                )
            )
            try:
                return rows[0]["id"]
            except IndexError:
                return self.insert(column_values, pk="id").last_pk
        else:
            pk = self.insert(column_values, pk="id").last_pk
            self.create_index(column_values.keys(), unique=True)
            return pk

    def m2m(
        self, other_table, record_or_list=None, pk=DEFAULT, lookup=None, m2m_table=None
    ):
        if isinstance(other_table, str):
            other_table = self.db.table(other_table, pk=pk)
        our_id = self.last_pk
        if lookup is not None:
            assert record_or_list is None, "Provide lookup= or record, not both"
        else:
            assert record_or_list is not None, "Provide lookup= or record, not both"
        tables = list(sorted([self.name, other_table.name]))
        columns = ["{}_id".format(t) for t in tables]
        if m2m_table is not None:
            m2m_table_name = m2m_table
        else:
            # Detect if there is a single, unambiguous option
            candidates = self.db.m2m_table_candidates(self.name, other_table.name)
            if len(candidates) == 1:
                m2m_table_name = candidates[0]
            elif len(candidates) > 1:
                raise NoObviousTable(
                    "No single obvious m2m table for {}, {} - use m2m_table= parameter".format(
                        self.name, other_table.name
                    )
                )
            else:
                # If not, create a new table
                m2m_table_name = m2m_table or "{}_{}".format(*tables)
        m2m_table = self.db.table(m2m_table_name, pk=columns, foreign_keys=columns)
        if lookup is None:
            records = (
                [record_or_list]
                if not isinstance(record_or_list, (list, tuple))
                else record_or_list
            )
            # Ensure each record exists in other table
            for record in records:
                id = other_table.insert(record, pk=pk, replace=True).last_pk
                m2m_table.insert(
                    {
                        "{}_id".format(other_table.name): id,
                        "{}_id".format(self.name): our_id,
                    },
                    replace=True,
                )
        else:
            id = other_table.lookup(lookup)
            m2m_table.insert(
                {
                    "{}_id".format(other_table.name): id,
                    "{}_id".format(self.name): our_id,
                },
                replace=True,
            )
        return self


class View(Queryable):
    def exists(self):
        return True

    def __repr__(self):
        return "<View {} ({})>".format(
            self.name, ", ".join(c.name for c in self.columns)
        )

    def drop(self):
        self.db.conn.execute("DROP VIEW [{}]".format(self.name))


def chunks(sequence, size):
    iterator = iter(sequence)
    for item in iterator:
        yield itertools.chain([item], itertools.islice(iterator, size - 1))


def jsonify_if_needed(value):
    if isinstance(value, decimal.Decimal):
        return float(value)
    if isinstance(value, (dict, list, tuple)):
        return json.dumps(value, default=repr)
    elif isinstance(value, (datetime.time, datetime.date, datetime.datetime)):
        return value.isoformat()
    else:
        return value


def _hash(record):
    return hashlib.sha1(
        json.dumps(record, separators=(",", ":"), sort_keys=True, default=repr).encode(
            "utf8"
        )
    ).hexdigest()


def resolve_extracts(extracts):
    if extracts is None:
        extracts = {}
    if isinstance(extracts, (list, tuple)):
        extracts = {item: item for item in extracts}
    return extracts


def validate_column_names(columns):
    # Validate no columns contain '[' or ']' - #86
    for column in columns:
        assert (
            "[" not in column and "]" not in column
        ), "'[' and ']' cannot be used in column names"