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lookml_parser.py
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lookml_parser.py
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import functools
import glob
import logging
import operator
import os
from dataclasses import dataclass
from typing import Dict, List, Optional, Set, Tuple
try:
import lkml
except ImportError:
print("Please install metaphor[looker] extra\n")
raise
from metaphor.common.entity_id import (
EntityId,
to_dataset_entity_id,
to_virtual_view_entity_id,
)
from metaphor.common.logger import get_logger, json_dump_to_debug_file
from metaphor.common.utils import unique_list
from metaphor.looker.config import LookerConnectionConfig
from metaphor.models.metadata_change_event import (
AssetStructure,
EntityType,
EntityUpstream,
LookerExplore,
LookerExploreJoin,
LookerView,
LookerViewDimension,
LookerViewMeasure,
SystemTag,
SystemTags,
SystemTagSource,
VirtualView,
VirtualViewLogicalID,
VirtualViewQuery,
VirtualViewType,
)
logger = get_logger()
# lkml parser's debug log can be very noisy
logging.getLogger("lkml.parser").setLevel(logging.WARNING)
@dataclass
class Explore:
name: str
@staticmethod
def from_dict(
raw_explore: Dict,
):
return Explore(
name=raw_explore["name"],
)
@dataclass
class RawModel:
raw_views: Dict[str, Dict]
raw_explores: Dict[str, Dict]
@dataclass
class Model:
explores: Dict[str, Explore]
@staticmethod
def from_dict(
raw_model: RawModel,
):
explores = [
# Ignore refinements since they don't change the sources
# See https://docs.looker.com/data-modeling/learning-lookml/refinements
Explore.from_dict(raw_explore)
for raw_explore in raw_model.raw_explores.values()
if not raw_explore["name"].startswith("+")
]
return Model(explores=dict((e.name, e) for e in explores))
ModelMap = Dict[str, Model]
_parsed_files: Dict[str, Dict] = {}
def _parse_lookml_file(path, base_dir) -> Dict:
if path in _parsed_files:
return _parsed_files[path]
with open(path) as f:
model = lkml.load(f)
_parsed_files[path] = model
sanitized = os.path.relpath(path, base_dir).replace("/", "__")
json_dump_to_debug_file(model, f"{sanitized}.json")
return model
def _to_dataset_id(source_name: str, connection: LookerConnectionConfig) -> EntityId:
parts = source_name.split(".")
if len(parts) == 1:
# table
if connection.default_schema is None:
raise ValueError(
f"Default schema is required for the connection {connection.database}"
)
full_name = f"{connection.database}.{connection.default_schema}.{source_name}"
elif len(parts) == 2:
# schema.table
full_name = f"{connection.database}.{source_name}"
elif len(parts) == 3:
# db.schema.table
full_name = source_name
else:
raise ValueError(f"Invalid source name {source_name}")
# Normalize dataset name by lower casing & dropping the quotation marks
full_name = full_name.replace('"', "").replace("`", "").lower()
return to_dataset_entity_id(full_name, connection.platform, connection.account)
def _get_upstream_and_query(
model_name: str,
view_name: str,
raw_model: RawModel,
connection: LookerConnectionConfig,
) -> Tuple[Set[EntityId], Optional[VirtualViewQuery]]:
raw_views = raw_model.raw_views
raw_view = raw_views.get(view_name)
if raw_view is None:
logger.error(f"Refer to non-existing view {view_name}")
return set(), None
if "upstream_entity_ids" in raw_view:
return raw_view["upstream_entity_ids"], raw_view["query"]
upstreams = set() # upstream dataset id or virtual view id
query = None
# Set upstream via derived_table
# https://docs.looker.com/reference/view-params/derived_table
derived_table: Optional[Dict] = raw_view.get("derived_table")
if derived_table is not None:
if "sql" in derived_table:
query = VirtualViewQuery(
query=derived_table["sql"],
source_platform=connection.platform,
source_dataset_account=connection.account,
default_database=connection.database,
default_schema=connection.default_schema,
)
# https://docs.looker.com/data-modeling/learning-lookml/creating-ndts
if "explore_source" in derived_table:
explore_name = derived_table["explore_source"]["name"]
raw_explore = raw_model.raw_explores.get(explore_name)
assert raw_explore is not None, f"Invalid explore_source: {explore_name}"
base_view_name = _get_base_view_name(raw_explore, raw_model)
if base_view_name is None:
base_view_name = explore_name
assert base_view_name in raw_views, f"Invalid base view {base_view_name}"
# TODO: handle field mapping
upstreams.add(
to_virtual_view_entity_id(
fullname(model_name, base_view_name), VirtualViewType.LOOKER_VIEW
)
)
# Set upstream via sql_table_name
# https://docs.looker.com/reference/view-params/sql_table_name-for-view
sql_table_name: Optional[str] = raw_view.get("sql_table_name")
if sql_table_name is not None:
upstreams = {_to_dataset_id(sql_table_name, connection)}
# If none of the above was triggered, assume upstream is a table with the same name
# https://docs.looker.com/reference/view-params/sql_table_name-for-view
if query is None and len(upstreams) == 0:
upstreams.add(_to_dataset_id(view_name, connection))
raw_view["upstream_entity_ids"] = upstreams
raw_view["query"] = query
return upstreams, query
def fullname(model: str, name: str) -> str:
return f"{model}.{name}"
def _get_model_asset_structure(
model: str, name: str, explore_view_folder_name: str
) -> AssetStructure:
return AssetStructure(
directories=[explore_view_folder_name, model],
name=name,
)
def _build_looker_view(
model: str,
raw_view: Dict,
raw_model: RawModel,
connection: LookerConnectionConfig,
explore_view_folder_name: str,
url: Optional[str],
) -> VirtualView:
name = raw_view["name"]
view = LookerView(
label=raw_view.get("label"),
url=url,
)
source_entities = []
try:
upstream_entity_ids, query = _get_upstream_and_query(
model, name, raw_model, connection
)
if upstream_entity_ids:
source_entities = [str(entity_id) for entity_id in upstream_entity_ids]
view.source_datasets = [
str(entity_id)
for entity_id in upstream_entity_ids
if entity_id.type == EntityType.DATASET
] or None
if query is not None:
view.query = query
except Exception:
logger.exception(f"Can't determine upstream for view {name}")
if "dimensions" in raw_view:
view.dimensions = [
LookerViewDimension(
field=raw_dimension["name"],
data_type=raw_dimension.get("type", raw_dimension["name"]),
)
for raw_dimension in raw_view["dimensions"]
]
if "measures" in raw_view:
view.measures = [
LookerViewMeasure(
field=raw_measure["name"],
type=raw_measure.get("type", "N/A"),
)
for raw_measure in raw_view["measures"]
]
return VirtualView(
logical_id=VirtualViewLogicalID(
name=fullname(model, name), type=VirtualViewType.LOOKER_VIEW
),
looker_view=view,
structure=_get_model_asset_structure(model, name, explore_view_folder_name),
entity_upstream=(
EntityUpstream(source_entities=source_entities) if source_entities else None
),
)
def _get_base_view_name(raw_explore: Dict, raw_model: RawModel) -> str:
# https://docs.looker.com/reference/explore-params/from-for-explore
if "from" in raw_explore:
return raw_explore["from"]
# https://docs.looker.com/reference/explore-params/view_name
if "view_name" in raw_explore:
return raw_explore["view_name"]
# Default to the view with the same name if nothing is specified
return raw_explore["name"]
def _build_looker_explore(
model: str,
raw_explore: Dict,
raw_model: RawModel,
explore_view_folder_name: str,
url: Optional[str],
) -> VirtualView:
name = raw_explore["name"]
base_view_name = _get_base_view_name(raw_explore, raw_model)
tag_names: List[str] = raw_explore.get("tags", [])
explore = LookerExplore(
model_name=model,
description=raw_explore.get("description"),
label=raw_explore.get("label"),
url=url,
fields=raw_explore.get("fields"),
base_view=str(
to_virtual_view_entity_id(
fullname(model, base_view_name), VirtualViewType.LOOKER_VIEW
)
),
)
if "extends" in raw_explore:
explore.extends = [
str(
to_virtual_view_entity_id(
fullname(model, explore), VirtualViewType.LOOKER_EXPLORE
)
)
for explore in raw_explore["extends"]
]
if "joins" in raw_explore:
explore.joins = [
LookerExploreJoin(
view=str(
to_virtual_view_entity_id(
fullname(model, raw_join.get("from", raw_join["name"])),
VirtualViewType.LOOKER_VIEW,
)
),
fields=raw_join.get("fields"),
on_clause=raw_join.get("sql_on"),
where_clause=raw_join.get("sql_where"),
type=raw_join.get("type", "left_outer"),
relationship=raw_join.get("relationship", "many_to_one"),
)
for raw_join in raw_explore["joins"]
]
# TODO: combine access_filters, always_filters and conditional_filters into explore.filters
# combine base view and joined view into source entities
source_entities = unique_list(
[explore.base_view] + [join.view for join in explore.joins or []]
)
tags = [
SystemTag(key=None, system_tag_source=SystemTagSource.LOOKER, value=value)
for value in tag_names
]
return VirtualView(
logical_id=VirtualViewLogicalID(
name=fullname(model, name), type=VirtualViewType.LOOKER_EXPLORE
),
looker_explore=explore,
structure=_get_model_asset_structure(model, name, explore_view_folder_name),
entity_upstream=EntityUpstream(source_entities=source_entities),
system_tags=SystemTags(tags=tags),
)
def _get_extended_names(raw_view_or_explore: Dict) -> Optional[List[str]]:
# Depending on the version of lkml, the "extends" field can be mapped to either "extends" or "extends__all"
extends = raw_view_or_explore.get(
"extends", raw_view_or_explore.get("extends__all", None)
)
if extends is None:
return None
# Flatten the nested list into a list of names
return functools.reduce(operator.concat, extends)
def _extend_view(raw_view: Dict, raw_views: Dict[str, Dict]) -> Dict:
"""Extends a view by merging parameters from extended views
See https://docs.looker.com/reference/view-params/extends-for-view
"""
def merge_views(base: Dict, extension: Dict) -> Dict:
# Conflict resolution in LookML extensions is quite complicated.
# We're only approximating the behavior here for the metadata we care about.
# See https://docs.looker.com/data-modeling/learning-lookml/extends#combining_parameters
merged = dict(base)
for key, val in extension.items():
if key == "extension":
# "extension" should not get merged
pass
elif key == "sql_table_name":
# merging "sql_table_name" should also clear "derived_table"
merged.pop("derived_table", None)
merged[key] = val
elif key == "derived_table":
# merge "derived_table" only if "sql" or "explore_source" is set in value
# also clear "sql_table_name"
if "sql" in val or "explore_source" in val:
merged.pop("sql_table_name", None)
merged[key] = val
else:
merged[key] = val
return merged
extended_view_names = _get_extended_names(raw_view)
if extended_view_names is None:
return raw_view
# Priority is given to views based on the order in the list.
# https://docs.looker.com/data-modeling/learning-lookml/extends#extending_more_than_one_object_at_the_same_time
merged_view: Dict = {}
for view_name in extended_view_names:
extended_view = raw_views.get(view_name, None)
assert extended_view is not None, f"Extending non-existing view {view_name}"
# It's possible to chain extends
# https://docs.looker.com/data-modeling/learning-lookml/extends#chaining_together_multiple_extends
chained_extended_view = _extend_view(extended_view, raw_views)
merged_view = merge_views(merged_view, chained_extended_view)
return merge_views(merged_view, raw_view)
def _extend_explore(raw_explore: Dict, raw_explores: Dict[str, Dict]) -> Dict:
"""Extends a view by merging parameters from extended views
See https://docs.looker.com/reference/view-params/extends-for-view
"""
def merge_explores(base: Dict, extension: Dict) -> Dict:
# Conflict resolution in LookML extensions is quite complicated.
# We're only approximating the behavior here for the metadata we care about.
# See https://docs.looker.com/data-modeling/learning-lookml/extends#combining_parameters
merged = dict(base)
for key, val in extension.items():
if key == "extension":
# "extension" should not get merged
# https://docs.looker.com/reference/view-params/extension-for-view
pass
elif key == "from" or key == "view_name":
# "from" & "view_name" are mutually exclusive when merging
merged.pop("view_name", None)
merged.pop("from", None)
merged[key] = val
else:
merged[key] = val
return merged
extended_explore_names = _get_extended_names(raw_explore)
if extended_explore_names is None:
return raw_explore
# Priority is given to explores based on the order in the list.
# https://docs.looker.com/data-modeling/learning-lookml/extends#extending_more_than_one_object_at_the_same_time
merged_explore: Dict = {}
for explore_name in extended_explore_names:
extended_explore = raw_explores.get(explore_name, None)
assert extended_explore is not None, f"Extending invalid explore {explore_name}"
# It's possible to chain extends
# https://docs.looker.com/data-modeling/learning-lookml/extends#chaining_together_multiple_extends
chained_extended_explore = _extend_explore(extended_explore, raw_explores)
merged_explore = merge_explores(merged_explore, chained_extended_explore)
return merge_explores(merged_explore, raw_explore)
def _resolve_model(raw_model: RawModel) -> RawModel:
resolved_views = {}
for name, view in raw_model.raw_views.items():
resolved_views[name] = _extend_view(view, raw_model.raw_views)
resolved_explores = {}
for name, explore in raw_model.raw_explores.items():
resolved_explores[name] = _extend_explore(explore, raw_model.raw_explores)
return RawModel(
raw_views=resolved_views,
raw_explores=resolved_explores,
)
def _get_entity_url(
path: str, base_dir: str, projectSourceUrl: Optional[str]
) -> Optional[str]:
if not projectSourceUrl:
return None
relative_path = os.path.relpath(path, base_dir)
return f"{projectSourceUrl}/{relative_path}"
def _to_absolute_include(include_path: str, file_path: str, base_dir: str) -> str:
"""Convert a relative include path into an absolute include"""
if include_path.startswith("/"):
return include_path
rel_dir = os.path.relpath(os.path.dirname(file_path), base_dir)
return f"/{rel_dir}/{include_path}"
def _load_included_file(
include_path: str,
base_dir: str,
projectSourceUrl: Optional[str],
raw_views: Dict[str, Dict],
raw_explores: Dict[str, Dict],
entity_urls: Dict[str, Optional[str]],
processed_files: Set[str],
):
"""Load all files matched by the pattern defined in include_path
All parsed views and explores will be added to raw_views & raw_explores, along with a
corresponding URL in entity_urls. This function will also recursively load any additional
files includes by each file.
"""
glob_pattern = f"{base_dir}/{include_path}"
if not glob_pattern.endswith(".lkml"):
glob_pattern = glob_pattern + ".lkml"
for file_path in glob.glob(glob_pattern, recursive=True):
# Skip processed files to avoid circular includes
normpath = os.path.normpath(file_path)
if normpath in processed_files:
continue
processed_files.add(normpath)
url = _get_entity_url(file_path, base_dir, projectSourceUrl)
logger.info(f"Processing view file {normpath}")
root = _parse_lookml_file(file_path, base_dir)
for view in root.get("views", []):
raw_views[view["name"]] = view
entity_urls[view["name"]] = url
for explore in root.get("explores", []):
raw_explores[explore["name"]] = explore
entity_urls[explore["name"]] = url
# A file can further include other files
# https://docs.looker.com/reference/model-params/include#using_include_in_a_view_file
for include_path in root.get("includes", []):
# Convert to absolute include
include_path = _to_absolute_include(include_path, file_path, base_dir)
_load_included_file(
include_path,
base_dir,
projectSourceUrl,
raw_views,
raw_explores,
entity_urls,
processed_files,
)
def _load_model(
model_path: str,
base_dir: str,
connections: Dict[str, LookerConnectionConfig],
projectSourceUrl: Optional[str],
) -> Tuple[RawModel, Dict[str, Optional[str]], LookerConnectionConfig]:
"""
Loads model file and extract raw Views and Explores
"""
model = _parse_lookml_file(model_path, base_dir)
logger.info(f"Processing model {model_path}")
raw_views: Dict[str, Dict] = {}
raw_explores: Dict[str, Dict] = {}
entity_urls: Dict[str, Optional[str]] = {}
# Add explores & views defined in included files
# https://docs.looker.com/reference/model-params/include#using_include_in_a_model_file
for include_path in model.get("includes", []):
# Convert to absolute include
include_path = _to_absolute_include(include_path, model_path, base_dir)
_load_included_file(
include_path,
base_dir,
projectSourceUrl,
raw_views,
raw_explores,
entity_urls,
set(),
)
url = _get_entity_url(model_path, base_dir, projectSourceUrl)
# Add explores & views defined in model
for explore in model.get("explores", []):
raw_explores[explore["name"]] = explore
entity_urls[explore["name"]] = url
for view in model.get("views", []):
raw_views[view["name"]] = view
entity_urls[view["name"]] = url
connection_name = model.get("connection", "").lower()
connection = connections.get(connection_name)
if connection is None:
raise ValueError(
f"Model {model_path} has an invalid connection {connection_name}"
)
raw_model = RawModel(raw_views=raw_views, raw_explores=raw_explores)
return raw_model, entity_urls, connection
def parse_project(
base_dir: str,
connections: Dict[str, LookerConnectionConfig],
explore_view_folder_name,
projectSourceUrl: Optional[str] = None,
) -> Tuple[ModelMap, List[VirtualView]]:
"""
parse the project under base_dir, returning a Model map and a list of virtual views including
Looker Explores and Views
https://docs.looker.com/data-modeling/getting-started/how-project-works
"""
model_map = {}
virtual_views = []
for model_path in glob.glob(f"{base_dir}/**/*.model.lkml", recursive=True):
model_name = os.path.basename(model_path)[0 : -len(".model.lkml")]
raw_model, entity_urls, connection = _load_model(
model_path, base_dir, connections, projectSourceUrl
)
resolved_model = _resolve_model(raw_model)
virtual_views.extend(
[
_build_looker_view(
model_name,
view,
resolved_model,
connection,
explore_view_folder_name,
entity_urls.get(view["name"]),
)
for view in resolved_model.raw_views.values()
# Exclude views that require extension
# https://docs.looker.com/reference/view-params/extension-for-view
if view.get("extension", "") != "required"
]
)
virtual_views.extend(
[
_build_looker_explore(
model_name,
explore,
resolved_model,
explore_view_folder_name,
entity_urls.get(explore["name"]),
)
for explore in resolved_model.raw_explores.values()
# Exclude explores that require extension
# https://docs.looker.com/reference/view-params/extension-for-view
if explore.get("extension", "") != "required"
]
)
model_map[model_name] = Model.from_dict(raw_model)
return model_map, virtual_views