Indexing and Performance

def create_index(self, key_or_list, cache_for=300, session=None, **kwargs):
    """
    Create an index on the collection.

    Parameters:
    - key_or_list: str or list, index key specification
    - cache_for: int, index cache duration (ignored)
    - session: ClientSession, session to use (ignored)
    - **kwargs: index options (unique, sparse, etc.)

    Returns:
    str: index name

    Raises:
    OperationFailure: if index creation fails
    """

def create_indexes(self, indexes, session=None):
    """
    Create multiple indexes.

    Parameters:
    - indexes: list, list of IndexModel instances or index specifications
    - session: ClientSession, session to use (ignored)

    Returns:
    list: list of created index names

    Raises:
    OperationFailure: if index creation fails
    """

from mongomock import ASCENDING, DESCENDING

collection = mongomock.MongoClient().db.users

# Create single field index
index_name = collection.create_index('email')

# Create index with direction
index_name = collection.create_index([('age', ASCENDING)])

# Create compound index
index_name = collection.create_index([
    ('status', ASCENDING),
    ('created_at', DESCENDING)
])

# Create unique index
index_name = collection.create_index('username', unique=True)

# Create sparse index (only indexes documents with the field)
index_name = collection.create_index('phone', sparse=True)

# Create index with custom name
index_name = collection.create_index('email', name='email_unique_idx')

# Create multiple indexes at once
indexes = [
    [('name', ASCENDING)],
    [('age', ASCENDING), ('status', ASCENDING)],
    [('created_at', DESCENDING)]
]
index_names = collection.create_indexes(indexes)

def list_indexes(self, session=None):
    """
    List all indexes on the collection.

    Parameters:
    - session: ClientSession, session to use (ignored)

    Returns:
    CommandCursor: cursor over index information documents
    """

def index_information(self, session=None):
    """
    Get detailed information about all indexes.

    Parameters:
    - session: ClientSession, session to use (ignored)

    Returns:
    dict: mapping of index names to index information
    """

collection = mongomock.MongoClient().db.users

# List all indexes
indexes_cursor = collection.list_indexes()
for index in indexes_cursor:
    print(f"Index: {index['name']}, Key: {index['key']}")

# Get index information dictionary
index_info = collection.index_information()
for name, info in index_info.items():
    print(f"Index {name}: {info}")

# Check if specific index exists
if 'email_1' in index_info:
    print("Email index exists")

def drop_index(self, index_or_name, session=None):
    """
    Drop a single index.

    Parameters:
    - index_or_name: str or list, index name or key specification
    - session: ClientSession, session to use (ignored)

    Returns:
    None

    Raises:
    OperationFailure: if index doesn't exist or drop fails
    """

def drop_indexes(self, session=None):
    """
    Drop all indexes except the default _id index.

    Parameters:
    - session: ClientSession, session to use (ignored)

    Returns:
    None

    Raises:
    OperationFailure: if drop operation fails
    """

collection = mongomock.MongoClient().db.users

# Drop index by name
collection.drop_index('email_1')

# Drop index by key specification
collection.drop_index([('age', 1)])

# Drop all indexes (except _id)
collection.drop_indexes()

# Handle errors
try:
    collection.drop_index('nonexistent_index')
except mongomock.OperationFailure as e:
    print(f"Index drop failed: {e}")

# Basic single field index
collection.create_index('field_name')

# Single field with direction
collection.create_index([('field_name', DESCENDING)])

# Multiple field index
collection.create_index([
    ('field1', ASCENDING),
    ('field2', DESCENDING),
    ('field3', ASCENDING)
])

# Unique constraint
collection.create_index('email', unique=True)

# Sparse index (only documents with the field)
collection.create_index('optional_field', sparse=True)

# Partial index with filter
collection.create_index('status', partialFilterExpression={
    'status': {'$in': ['active', 'pending']}
})

# TTL index (time-to-live)
collection.create_index('expiry_date', expireAfterSeconds=3600)

# Case-insensitive index
collection.create_index('name', collation={
    'locale': 'en_US',
    'strength': 2
})

collection = mongomock.MongoClient().db.users

# Create various index types
collection.create_index('email', unique=True, sparse=True)

collection.create_index([
    ('department', ASCENDING),
    ('hire_date', DESCENDING)
], name='dept_hire_idx')

# TTL index for session cleanup
collection.create_index('last_access', expireAfterSeconds=1800)

# Partial index for active users only
collection.create_index('performance_score', 
    partialFilterExpression={'status': 'active'})

collection = mongomock.MongoClient().db.users

# Index supports efficient queries
collection.create_index([('status', 1), ('created_at', -1)])

# Efficient query (uses index)
recent_active = collection.find({
    'status': 'active',
    'created_at': {'$gte': datetime(2023, 1, 1)}
}).sort('created_at', -1)

# Index prefix usage
status_query = collection.find({'status': 'active'})  # Uses index prefix

# Monitor index usage
index_stats = collection.index_information()
for name, info in index_stats.items():
    print(f"Index {name} has key: {info.get('key')}")

# Rebuild indexes if needed
collection.drop_indexes()
collection.create_index([('status', 1), ('created_at', -1)])

# Index naming patterns
def gen_index_name(index_list):
    """
    Generate index name from key specification.

    Parameters:
    - index_list: list, list of (key, direction) tuples

    Returns:
    str: generated index name
    """

from mongomock.helpers import gen_index_name

# Automatic name generation
index_spec = [('email', 1), ('status', 1)]
auto_name = gen_index_name(index_spec)  # 'email_1_status_1'

# Custom index names
collection.create_index('email', name='users_email_unique')
collection.create_index([('dept', 1), ('role', 1)], name='dept_role_idx')

# Descriptive naming convention
collection.create_index('created_at', name='users_created_desc', 
                       background=True)

# Helper functions for index management
def create_index_list(key_or_list, direction=None):
    """
    Create standardized index specification.

    Parameters:
    - key_or_list: str or list, index key specification
    - direction: int, default direction for string keys

    Returns:
    list: standardized list of (key, direction) tuples
    """

from mongomock.helpers import create_index_list

# Convert various formats to standard format
spec1 = create_index_list('email')  # [('email', 1)]
spec2 = create_index_list('age', -1)  # [('age', -1)]
spec3 = create_index_list([('name', 1), ('age', -1)])  # unchanged

# Use in index operations
for spec in [spec1, spec2, spec3]:
    index_name = collection.create_index(spec)
    print(f"Created index: {index_name}")

# Sort/Index directions
ASCENDING = 1
DESCENDING = -1

# Index types (for documentation)
TEXT = 'text'
GEOSPHERE = '2dsphere'
HASHED = 'hashed'