Refactor block_using_rules_sql to follow normal pattern and avoid confusion

splink/analyse_blocking.py

@@ -5,7 +5,7 @@
 
 import pandas as pd
 
-from .blocking import BlockingRule, _sql_gen_where_condition, block_using_rules_sql
+from .blocking import BlockingRule, _sql_gen_where_condition, block_using_rules_sqls
 from .misc import calculate_cartesian, calculate_reduction_ratio
 
 # https://stackoverflow.com/questions/39740632/python-type-hinting-without-cyclic-imports
@@ -83,16 +83,17 @@ def cumulative_comparisons_generated_by_blocking_rules(
         cartesian = calculate_cartesian(row_count_df, settings_obj._link_type)
 
     # Calculate the total number of rows generated by each blocking rule
-    sql = block_using_rules_sql(linker)
-    linker._enqueue_sql(sql, "__splink__df_blocked_data")
+    sqls = block_using_rules_sqls(linker)
+    for sql in sqls:
+        linker._enqueue_sql(sql["sql"], sql["output_table_name"])
 
     brs_as_objs = linker._settings_obj_._blocking_rules_to_generate_predictions
 
     sql = """
         select
         count(*) as row_count,
         match_key
-        from __splink__df_blocked_data
+        from __splink__df_blocked
         group by match_key
         order by cast(match_key as int) asc
     """

splink/blocking.py

@@ -197,7 +197,7 @@ def _sql_gen_where_condition(link_type, unique_id_cols):
 
 
 # flake8: noqa: C901
-def block_using_rules_sql(linker: Linker):
+def block_using_rules_sqls(linker: Linker):
     """Use the blocking rules specified in the linker's settings object to
     generate a SQL statement that will create pairwise record comparions
     according to the blocking rule(s).
@@ -206,6 +206,54 @@ def block_using_rules_sql(linker: Linker):
     so that duplicate comparisons are not generated.
     """
 
+    sqls = []
+
+    # For the two dataset link only, rather than a self join of
+    # __splink__df_concat_with_tf, it's much faster to split the input
+    # into two tables, and join (because then Splink doesn't have to evaluate)
+    # intra-dataset comparisons.
+    # see https://github.com/moj-analytical-services/splink/pull/1359
+    if (
+        linker._two_dataset_link_only
+        and not linker._find_new_matches_mode
+        and not linker._compare_two_records_mode
+    ):
+        source_dataset_col = linker._source_dataset_column_name
+        # Need df_l to be the one with the lowest id to preeserve the property
+        # that the left dataset is the one with the lowest concatenated id
+        keys = linker._input_tables_dict.keys()
+        keys = list(sorted(keys))
+        df_l = linker._input_tables_dict[keys[0]]
+        df_r = linker._input_tables_dict[keys[1]]
+
+        # This also needs to work for training u
+        if linker._train_u_using_random_sample_mode:
+            spl_switch = "_sample"
+        else:
+            spl_switch = ""
+
+        sql = f"""
+        select * from __splink__df_concat_with_tf{spl_switch}
+        where {source_dataset_col} = '{df_l.templated_name}'
+        """
+        sqls.append(
+            {
+                "sql": sql,
+                "output_table_name": f"__splink__df_concat_with_tf{spl_switch}_left",
+            }
+        )
+
+        sql = f"""
+        select * from __splink__df_concat_with_tf{spl_switch}
+        where {source_dataset_col} = '{df_r.templated_name}'
+        """
+        sqls.append(
+            {
+                "sql": sql,
+                "output_table_name": f"__splink__df_concat_with_tf{spl_switch}_right",
+            }
+        )
+
     if type(linker).__name__ in ["SparkLinker"]:
         apply_salt = True
     else:
@@ -243,36 +291,6 @@ def block_using_rules_sql(linker: Linker):
             " will not be implemented for this run."
         )
 
-    if (
-        linker._two_dataset_link_only
-        and not linker._find_new_matches_mode
-        and not linker._compare_two_records_mode
-    ):
-        source_dataset_col = linker._source_dataset_column_name
-        # Need df_l to be the one with the lowest id to preeserve the property
-        # that the left dataset is the one with the lowest concatenated id
-        keys = linker._input_tables_dict.keys()
-        keys = list(sorted(keys))
-        df_l = linker._input_tables_dict[keys[0]]
-        df_r = linker._input_tables_dict[keys[1]]
-
-        if linker._train_u_using_random_sample_mode:
-            sample_switch = "_sample"
-        else:
-            sample_switch = ""
-
-        sql = f"""
-        select * from __splink__df_concat_with_tf{sample_switch}
-        where {source_dataset_col} = '{df_l.templated_name}'
-        """
-        linker._enqueue_sql(sql, f"__splink__df_concat_with_tf{sample_switch}_left")
-
-        sql = f"""
-        select * from __splink__df_concat_with_tf{sample_switch}
-        where {source_dataset_col} = '{df_r.templated_name}'
-        """
-        linker._enqueue_sql(sql, f"__splink__df_concat_with_tf{sample_switch}_right")
-
     # Cover the case where there are no blocking rules
     # This is a bit of a hack where if you do a self-join on 'true'
     # you create a cartesian product, rather than having separate code
@@ -287,7 +305,7 @@ def block_using_rules_sql(linker: Linker):
     else:
         probability = ""
 
-    sqls = []
+    br_sqls = []
     for br in blocking_rules:
         # Apply our salted rules to resolve skew issues. If no salt was
         # selected to be added, then apply the initial blocking rule.
@@ -310,8 +328,10 @@ def block_using_rules_sql(linker: Linker):
             {where_condition}
             """
 
-            sqls.append(sql)
+            br_sqls.append(sql)
+
+    sql = "union all".join(br_sqls)
 
-    sql = "union all".join(sqls)
+    sqls.append({"sql": sql, "output_table_name": "__splink__df_blocked"})
 
-    return sql
+    return sqls

splink/em_training_session.py

@@ -4,7 +4,7 @@
 from copy import deepcopy
 from typing import TYPE_CHECKING
 
-from .blocking import BlockingRule, block_using_rules_sql
+from .blocking import BlockingRule, block_using_rules_sqls
 from .charts import (
     m_u_parameters_interactive_history_chart,
     match_weights_interactive_history_chart,
@@ -151,8 +151,9 @@ def _comparison_vectors(self):
 
         nodes_with_tf = self._original_linker._initialise_df_concat_with_tf()
 
-        sql = block_using_rules_sql(self._training_linker)
-        self._training_linker._enqueue_sql(sql, "__splink__df_blocked")
+        sqls = block_using_rules_sqls(self._training_linker)
+        for sql in sqls:
+            self._training_linker._enqueue_sql(sql["sql"], sql["output_table_name"])
 
         # repartition after blocking only exists on the SparkLinker
         repartition_after_blocking = getattr(

splink/estimate_u.py

@@ -4,7 +4,7 @@
 from copy import deepcopy
 from typing import TYPE_CHECKING
 
-from .blocking import block_using_rules_sql
+from .blocking import block_using_rules_sqls
 from .comparison_vector_values import compute_comparison_vector_values_sql
 from .expectation_maximisation import (
     compute_new_parameters_sql,
@@ -106,8 +106,9 @@ def estimate_u_values(linker: Linker, max_pairs, seed=None):
 
     settings_obj._blocking_rules_to_generate_predictions = []
 
-    sql = block_using_rules_sql(training_linker)
-    training_linker._enqueue_sql(sql, "__splink__df_blocked")
+    sqls = block_using_rules_sqls(training_linker)
+    for sql in sqls:
+        training_linker._enqueue_sql(sql["sql"], sql["output_table_name"])
 
     # repartition after blocking only exists on the SparkLinker
     repartition_after_blocking = getattr(

splink/linker.py

@@ -33,7 +33,7 @@
 )
 from .blocking import (
     BlockingRule,
-    block_using_rules_sql,
+    block_using_rules_sqls,
     blocking_rule_to_obj,
 )
 from .cache_dict_with_logging import CacheDictWithLogging
@@ -1406,8 +1406,9 @@ def deterministic_link(self) -> SplinkDataFrame:
         self._deterministic_link_mode = True
 
         concat_with_tf = self._initialise_df_concat_with_tf()
-        sql = block_using_rules_sql(self)
-        self._enqueue_sql(sql, "__splink__df_blocked")
+        sqls = block_using_rules_sqls(self)
+        for sql in sqls:
+            self._enqueue_sql(sql["sql"], sql["output_table_name"])
         return self._execute_sql_pipeline([concat_with_tf])
 
     def estimate_u_using_random_sampling(
@@ -1728,8 +1729,9 @@ def predict(
         if nodes_with_tf:
             input_dataframes.append(nodes_with_tf)
 
-        sql = block_using_rules_sql(self)
-        self._enqueue_sql(sql, "__splink__df_blocked")
+        sqls = block_using_rules_sqls(self)
+        for sql in sqls:
+            self._enqueue_sql(sql["sql"], sql["output_table_name"])
 
         repartition_after_blocking = getattr(self, "repartition_after_blocking", False)
 
@@ -1853,8 +1855,9 @@ def find_matches_to_new_records(
 
         add_unique_id_and_source_dataset_cols_if_needed(self, new_records_df)
 
-        sql = block_using_rules_sql(self)
-        self._enqueue_sql(sql, "__splink__df_blocked")
+        sqls = block_using_rules_sqls(self)
+        for sql in sqls:
+            self._enqueue_sql(sql["sql"], sql["output_table_name"])
 
         sql = compute_comparison_vector_values_sql(self._settings_obj)
         self._enqueue_sql(sql, "__splink__df_comparison_vectors")
@@ -1937,8 +1940,9 @@ def compare_two_records(self, record_1: dict, record_2: dict):
 
         self._enqueue_sql(sql_join_tf, "__splink__compare_two_records_right_with_tf")
 
-        sql = block_using_rules_sql(self)
-        self._enqueue_sql(sql, "__splink__df_blocked")
+        sqls = block_using_rules_sqls(self)
+        for sql in sqls:
+            self._enqueue_sql(sql["sql"], sql["output_table_name"])
 
         sql = compute_comparison_vector_values_sql(self._settings_obj)
         self._enqueue_sql(sql, "__splink__df_comparison_vectors")
@@ -1993,9 +1997,9 @@ def _self_link(self) -> SplinkDataFrame:
 
         nodes_with_tf = self._initialise_df_concat_with_tf()
 
-        sql = block_using_rules_sql(self)
-
-        self._enqueue_sql(sql, "__splink__df_blocked")
+        sqls = block_using_rules_sqls(self)
+        for sql in sqls:
+            self._enqueue_sql(sql["sql"], sql["output_table_name"])
 
         sql = compute_comparison_vector_values_sql(self._settings_obj)
 

splink/m_training.py

@@ -1,7 +1,7 @@
 import logging
 from copy import deepcopy
 
-from .blocking import BlockingRule, block_using_rules_sql
+from .blocking import BlockingRule, block_using_rules_sqls
 from .comparison_vector_values import compute_comparison_vector_values_sql
 from .expectation_maximisation import (
     compute_new_parameters_sql,
@@ -34,8 +34,10 @@ def estimate_m_values_from_label_column(linker, df_dict, label_colname):
 
     concat_with_tf = linker._initialise_df_concat_with_tf()
 
-    sql = block_using_rules_sql(training_linker)
-    training_linker._enqueue_sql(sql, "__splink__df_blocked")
+    sqls = block_using_rules_sqls(training_linker)
+
+    for sql in sqls:
+        training_linker._enqueue_sql(sql["sql"], sql["output_table_name"])
 
     sql = compute_comparison_vector_values_sql(settings_obj)