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Document get_call_result_type() and friends; mark TypeGetTupleDesc()
and RelationNameGetTupleDesc() as deprecated; remove uses of the latter in the contrib library. Along the way, clean up crosstab() code and documentation a little.
This commit is contained in:
Tom Lane
@ -57,11 +57,16 @@ Installation:
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but you can create additional crosstab functions per the instructions
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in the documentation below.
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crosstab(text sql, N int)
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crosstab(text sql)
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- returns a set of row_name plus N category value columns
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- requires anonymous composite type syntax in the FROM clause. See
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the instructions in the documentation below.
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crosstab(text sql, N int)
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- obsolete version of crosstab()
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- the argument N is now ignored, since the number of value columns
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is always determined by the calling query
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connectby(text relname, text keyid_fld, text parent_keyid_fld
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[, text orderby_fld], text start_with, int max_depth
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[, text branch_delim])
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@ -133,7 +138,7 @@ Inputs
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A SQL statement which produces the source set of data. The SQL statement
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must return one row_name column, one category column, and one value
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column.
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column. row_name and value must be of type text.
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e.g. provided sql must produce a set something like:
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@ -152,15 +157,15 @@ Outputs
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Returns setof tablefunc_crosstab_N, which is defined by:
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CREATE VIEW tablefunc_crosstab_N AS
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SELECT
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''::TEXT AS row_name,
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''::TEXT AS category_1,
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''::TEXT AS category_2,
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CREATE TYPE tablefunc_crosstab_N AS (
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row_name TEXT,
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category_1 TEXT,
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category_2 TEXT,
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.
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.
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.
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''::TEXT AS category_N;
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category_N TEXT
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);
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for the default installed functions, where N is 2, 3, or 4.
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@ -188,31 +193,9 @@ Notes
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6. The installed defaults are for illustration purposes. You
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can create your own return types and functions based on the
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crosstab() function of the installed library.
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crosstab() function of the installed library. See below for
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details.
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The return type must have a first column that matches the data
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type of the sql set used as its source. The subsequent category
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columns must have the same data type as the value column of the
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sql result set.
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Create a VIEW to define your return type, similar to the VIEWS
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in the provided installation script. Then define a unique function
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name accepting one text parameter and returning setof your_view_name.
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For example, if your source data produces row_names that are TEXT,
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and values that are FLOAT8, and you want 5 category columns:
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CREATE VIEW my_crosstab_float8_5_cols AS
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SELECT
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''::TEXT AS row_name,
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0::FLOAT8 AS category_1,
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0::FLOAT8 AS category_2,
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0::FLOAT8 AS category_3,
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0::FLOAT8 AS category_4,
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0::FLOAT8 AS category_5;
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CREATE OR REPLACE FUNCTION crosstab_float8_5_cols(text)
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RETURNS setof my_crosstab_float8_5_cols
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AS '$libdir/tablefunc','crosstab' LANGUAGE 'c' STABLE STRICT;
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Example usage
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@ -241,11 +224,12 @@ select * from crosstab3(
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==================================================================
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Name
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crosstab(text, int) - returns a set of row_name
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plus N category value columns
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crosstab(text) - returns a set of row_names plus category value columns
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Synopsis
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crosstab(text sql)
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crosstab(text sql, int N)
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Inputs
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@ -271,15 +255,16 @@ Inputs
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N
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number of category value columns
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Obsolete argument; ignored if supplied (formerly this had to match
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the number of category columns determined by the calling query)
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Outputs
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Returns setof record, which must defined with a column definition
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Returns setof record, which must be defined with a column definition
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in the FROM clause of the SELECT statement, e.g.:
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SELECT *
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FROM crosstab(sql, 2) AS ct(row_name text, category_1 text, category_2 text);
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FROM crosstab(sql) AS ct(row_name text, category_1 text, category_2 text);
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the example crosstab function produces a set something like:
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<== values columns ==>
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@ -292,9 +277,12 @@ Notes
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1. The sql result must be ordered by 1,2.
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2. The number of values columns is determined at run-time. The
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column definition provided in the FROM clause must provide for
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N + 1 columns of the proper data types.
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2. The number of values columns is determined by the column definition
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provided in the FROM clause. The FROM clause must define one
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row_name column (of the same datatype as the first result column
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of the sql query) followed by N category columns (of the same
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datatype as the third result column of the sql query). You can
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set up as many category columns as you wish.
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3. Missing values (i.e. not enough adjacent rows of same row_name to
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fill the number of result values columns) are filled in with nulls.
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@ -304,6 +292,44 @@ Notes
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5. Rows with all nulls in the values columns are skipped.
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6. You can avoid always having to write out a FROM clause that defines the
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output columns by setting up a custom crosstab function that has
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the desired output row type wired into its definition.
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There are two ways you can set up a custom crosstab function:
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A. Create a composite type to define your return type, similar to the
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examples in the installation script. Then define a unique function
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name accepting one text parameter and returning setof your_type_name.
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For example, if your source data produces row_names that are TEXT,
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and values that are FLOAT8, and you want 5 category columns:
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CREATE TYPE my_crosstab_float8_5_cols AS (
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row_name TEXT,
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category_1 FLOAT8,
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category_2 FLOAT8,
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category_3 FLOAT8,
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category_4 FLOAT8,
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category_5 FLOAT8
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);
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CREATE OR REPLACE FUNCTION crosstab_float8_5_cols(text)
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RETURNS setof my_crosstab_float8_5_cols
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AS '$libdir/tablefunc','crosstab' LANGUAGE 'c' STABLE STRICT;
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B. Use OUT parameters to define the return type implicitly.
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The same example could also be done this way:
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CREATE OR REPLACE FUNCTION crosstab_float8_5_cols(IN text,
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OUT row_name TEXT,
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OUT category_1 FLOAT8,
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OUT category_2 FLOAT8,
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OUT category_3 FLOAT8,
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OUT category_4 FLOAT8,
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OUT category_5 FLOAT8)
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RETURNS setof record
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AS '$libdir/tablefunc','crosstab' LANGUAGE 'c' STABLE STRICT;
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Example usage
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@ -418,6 +444,10 @@ Notes
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5. Rows with a null row_name column are skipped.
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6. You can create predefined functions to avoid having to write out
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the result column names/types in each query. See the examples
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for crosstab(text).
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Example usage
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