Function approximate_row_count returns 0 for caggs

[pdipesh02]

The approximate_row_count function is executed directly on the user view instead of corresponding materialized hypertable which returns 0 for caggs. The function is updated to fetch the details for materialized hypertable information corresponding to cagg and then get the approximate_row_count for the materialized hypertable.

Fixes #6051

[codecov]

Codecov Report

Merging #6053 (f687a61) into main (ef783c4) will decrease coverage by 7.67%.
The diff coverage is n/a.

❗ Current head f687a61 differs from pull request most recent head 1f290fc. Consider uploading reports for the commit 1f290fc to get more accurate results

@@            Coverage Diff             @@
##             main    #6053      +/-   ##
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- Coverage   81.44%   73.77%   -7.67%     
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  Files         243      243              
  Lines       55948    49089    -6859     
  Branches    12389    12292      -97     
==========================================
- Hits        45566    36217    -9349     
+ Misses       8045     7148     -897     
- Partials     2337     5724    +3387     

see 223 files with indirect coverage changes

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[github-actions]

@akuzm, @shhnwz: please review this pull request.

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[fabriziomello]

Suggested change

	SELECT format('%I.%I', ht.schema_name, ht.table_name)::regclass FROM pg_class c
	INTO mat_ht
	INNER JOIN pg_namespace n ON (n.OID = c.relnamespace)
	INNER JOIN _timescaledb_catalog.continuous_agg a ON (a.user_view_schema = n.nspname AND a.user_view_name = c.relname)
	INNER JOIN _timescaledb_catalog.hypertable ht ON (a.mat_hypertable_id = ht.id)
	WHERE c.OID = relation;
	SELECT format('%I.%I', ht.schema_name, ht.table_name)::regclass
	INTO mat_ht
	FROM pg_class c
	JOIN pg_namespace n ON (n.OID = c.relnamespace)
	JOIN _timescaledb_catalog.continuous_agg a ON (a.user_view_schema = n.nspname AND a.user_view_name = c.relname)
	JOIN _timescaledb_catalog.hypertable ht ON (a.mat_hypertable_id = ht.id)
	WHERE c.OID = relation;

Nit. just cosmetic SQL formatting.

It is interesting that your SQL lead to a syntax error on psql console:

26528 (leader) fabrizio=# SELECT format('%I.%I', ht.schema_name, ht.table_name)::regclass FROM pg_class c INTO mat_ht
    INNER JOIN pg_namespace n ON (n.OID = c.relnamespace)
    INNER JOIN _timescaledb_catalog.continuous_agg a ON (a.user_view_schema = n.nspname AND a.user_view_name = c.relname)
    INNER JOIN _timescaledb_catalog.hypertable ht ON (a.mat_hypertable_id = ht.id)
    WHERE c.OID = 'conditions_summary'::regclass;
ERROR:  42601: syntax error at or near "INTO"
LINE 1: ...ma_name, ht.table_name)::regclass FROM pg_class c INTO mat_h...
                                                             ^
LOCATION:  scanner_yyerror, scan.l:1188

Probably it is a psql issue because your tests are passing, but with proposed reformatting it works perfect:

26528 (leader) fabrizio=# SELECT format('%I.%I', ht.schema_name, ht.table_name)::regclass
    INTO mat_ht
    FROM pg_class c
    JOIN pg_namespace n ON (n.OID = c.relnamespace)
    JOIN _timescaledb_catalog.continuous_agg a ON (a.user_view_schema = n.nspname AND a.user_view_name = c.relname)
    JOIN _timescaledb_catalog.hypertable ht ON (a.mat_hypertable_id = ht.id)
    WHERE c.OID = 'conditions_summary'::regclass;
SELECT 1

[pdipesh02]

Thanks @fabriziomello, I have formatted the SQL as suggested.

[fabriziomello]

Left a minor comment about reformatting SQL but LGTM.

[timescale-automation]

Automated backport to 2.11.x not done: cherry-pick failed.

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HEAD detached at origin/2.11.x
You are currently cherry-picking commit 93519d0af.
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Changes to be committed:
	new file:   .unreleased/bugfix_6053
	modified:   sql/size_utils.sql

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   tsl/test/expected/size_utils_tsl.out
	both modified:   tsl/test/sql/size_utils_tsl.sql

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