42P20

At a glance

42P20 (windowing_error) Window definitions constrain both calls and frame boundaries.

Meaning

The fixed core uses 42P20 for window-function placement or nesting errors and for invalid window-definition structure. Parser grammar rejects impossible frame start/end combinations; parse analysis rejects a window function in a clause that cannot contain it or another window function; named-window transformation rejects conflicting inheritance. A legal frame can still be empty for a particular row, so an empty result is not by itself a 42P20 signal.

Diagnosis

Classify the primary message before changing SQL. A frame message points to UNBOUNDED direction or start/end ordering; RANGE with an offset requires exactly one ORDER BY column and GROUPS requires an ORDER BY clause. A placement message names a clause such as WHERE, GROUP BY, JOIN, RETURNING, or a window definition, while the nested-call message means a window expression appears inside another window expression. Named-window messages distinguish duplicate definitions, attempts to override copied PARTITION BY or ORDER BY, and copying a window that already has a frame; OVER foo and OVER (foo) therefore have different inheritance behavior. The executor separately reports negative ROWS or GROUPS frame offsets as SQLSTATE 22013 (invalid_preceding_or_following_size), and null offsets as 22004; those are not 42P20.

Response

Move a nested calculation to an outer query level, or move the window expression out of the named clause identified by the message. Repair only the relevant frame grammar, add the required ordering for RANGE/GROUPS, and define one named window without conflicting overrides. Do not change a valid frame merely because it produces no rows for one current row. If this ERROR occurs inside an explicit transaction, issue ROLLBACK or ROLLBACK TO a savepoint created before the statement before retrying; autocommit can submit the corrected query after the failed statement returns to idle.

Messages

Representative fixed-source messages include:

• ERROR message: window function calls cannot be nested
• ERROR message: frame start cannot be UNBOUNDED FOLLOWING
• ERROR message: frame starting from following row cannot end with current row
• ERROR message: frame end cannot be UNBOUNDED PRECEDING
• ERROR message: frame starting from current row cannot have preceding rows
• ERROR message: frame starting from following row cannot have preceding rows
• ERROR message: window functions are not allowed in %s
• ERROR message: window "%s" is already defined
• ERROR message: cannot override PARTITION BY clause of window "%s"
• ERROR message: cannot override ORDER BY clause of window "%s"
• ERROR message: cannot copy window "%s" because it has a frame clause
• ERROR message: cannot copy window "%s" because it has a frame clause; HINT: Omit the parentheses in this OVER clause.
• ERROR message: RANGE with offset PRECEDING/FOLLOWING requires exactly one ORDER BY column
• ERROR message: GROUPS mode requires an ORDER BY clause

Placeholders are filled by the actual object, column, or parameter.

Versions

The locked catalogue shows this condition by PostgreSQL 8.4.0; behavior here is fixed to PostgreSQL 18.6 source. Catalogue presence is a range boundary, not proof that every message or feature began in that release.

Related

• 42P19
• 42803

Sources

Source messages, line anchors, and evidence limits are recorded in authored evidence.

• src/backend/executor/execExpr.c:1155-1157 (fixed source)
• src/backend/parser/gram.y:16499-16544 (fixed source)
• src/backend/parser/parse_agg.c:1041-1046 (fixed source)
• src/backend/parser/parse_clause.c:2790-2947 (fixed source)
• src/backend/executor/nodeWindowAgg.c:2139-2210 (fixed source)

Source evidence

Evidence belongs to the frozen source and runtime versions listed here. It is not a runtime verification of the selected manual version.

• src/backend/utils/errcodes.txt · REL_18_6 · line 344
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/executor/execExpr.c · REL_18_6 · lines 1155-1157
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/gram.y · REL_18_6 · lines 16499-16502
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/gram.y · REL_18_6 · lines 16504-16507
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/gram.y · REL_18_6 · lines 16528-16531
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/gram.y · REL_18_6 · lines 16534-16537
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/gram.y · REL_18_6 · lines 16541-16544
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/parse_agg.c · REL_18_6 · lines 1041-1046
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/parse_clause.c · REL_18_6 · lines 2790-2793
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/parse_clause.c · REL_18_6 · lines 2851-2855
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/parse_clause.c · REL_18_6 · lines 2863-2867
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/parse_clause.c · REL_18_6 · lines 2893-2897
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/parse_clause.c · REL_18_6 · lines 2899-2904
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/parse_clause.c · REL_18_6 · lines 2921-2924
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/parser/parse_clause.c · REL_18_6 · lines 2944-2947
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• src/backend/executor/nodeWindowAgg.c · REL_18_6 · lines 2139-2210
  724edf9bde9d356724ad384a2e196edc3c9f80f7
• raw/calls/REL_18_6.jsonl · ·

Message templates

window function calls cannot be nested

frame start cannot be UNBOUNDED FOLLOWING

frame starting from following row cannot end with current row

frame end cannot be UNBOUNDED PRECEDING

frame starting from current row cannot have preceding rows

frame starting from following row cannot have preceding rows

window functions are not allowed in %s

window "%s" is already defined

cannot override PARTITION BY clause of window "%s"

cannot override ORDER BY clause of window "%s"

cannot copy window "%s" because it has a frame clause

cannot copy window "%s" because it has a frame clause

Omit the parentheses in this OVER clause.

Omit the parentheses in this OVER clause.

RANGE with offset PRECEDING/FOLLOWING requires exactly one ORDER BY column

GROUPS mode requires an ORDER BY clause

Reproduction & repair cases

No reproduction case is attached to this condition.

Recorded runtime evidence

No runtime observation is attached to this entry.