sqlsmith: add initial support for PL/pgSQL

[DrewKimball]

plpgsql: add support for NULL statements

This commit implements the PL/pgSQL NULL statement, which is a no-op.
This will be convenient for the following commit, which adds initial
support for PL/pgSQL to sqlsmith.

Informs #117744
Informs #106368

Release note (sql change): Added support for the PL/pgSQL NULL statement.

sqlsmith: add initial support for PL/pgSQL

This commit adds initial support for PL/pgSQL routines. The following
statements are supported:

• Block
• If/Elsif/Else
• Return
• Null
• Assign
• SQL statements

Informs #106368

Release note: None

[blathers-crl]

Your pull request contains more than 1000 changes. It is strongly encouraged to split big PRs into smaller chunks.

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[DrewKimball]

The first three commits are #119034.

[cockroach-teamcity]

This change is 

[DrewKimball]

Example generated statement:

CREATE FUNCTION func_29()
	RETURNS RECORD
	LANGUAGE plpgsql
	AS $funcbody$
DECLARE
decl_205 NAME := e'C\x14':::STRING:::NAME;
"D
ecl_206" INET := '218.182.213.88/3':::INET;
"😃Decl_207" VOID;
decl_208 TIMETZ;
"de
   cl_209" REFCURSOR := e'q2Jm\x046j':::REFCURSOR;
"d e%pcl_210" REGTYPE := 1023113024:::OID;
BEGIN
"D
ecl_206" := "D
ecl_206";
RETURN (1461997381:::OID, '23:03:00.602946':::TIME, 783147277:::OID);
NULL;
SELECT e'w24G9,\x06%':::REFCURSOR AS col_3019, "t{ab_1855"."c.ol0__2" AS col_3020, '115.161.46.85/21':::INET AS col_3021 FROM defaultdb.public.tab_1110@"tab_1110_c.ol0__2_key" AS "t{ab_1855" LIMIT 89:::INT8;
IF false THEN
	DELETE FROM defaultdb.public.tab_1110 AS tab_1856 USING defaultdb.public.tab_1110 AS "tab\g_1857", defaultdb.public.tab_1110 AS tab_1858, defaultdb.public.tab_1110 AS t😰ab_1859, defaultdb.public.tab_1110 AS "ta\\u3F42b͌_1860" WHERE false LIMIT 25:::INT8;
ELSIF true THEN
	"d e%pcl_210" := 3429146290:::OID;
END IF;
END;
$funcbody$;

[yuzefovich]

Nice! I have a few nits.

Reviewed 3 of 3 files at r4, 5 of 5 files at r5, all commit messages.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @DrewKimball and @rytaft)

---

pkg/internal/sqlsmith/plpgsql.go line 90 at r5 (raw file):

	for i := 0; i < numStmts; i++ {
		for {
			// No need for a retry counter, because eventually a NULL statement will

I'm a bit confused by this comment - can you expand on it? Is it effectively saying that we don't need to count the number of times Next is called when it returns ok = false because at some point NULL stmt is returned which will have ok = true, so infinite loop is impossible?

---

pkg/internal/sqlsmith/plpgsql.go line 109 at r5 (raw file):

	}
	if s.coin() {
		numElsIfs := s.rnd.Intn(3) + 1

nit: perhaps s/numElsIfs/numElseIfs/.

---

pkg/internal/sqlsmith/plpgsql.go line 136 at r5 (raw file):

}

// TODO(#106368): implement generation for the remaining statements.

nit: this issue is being closed by this PR right now - should this refer to a different issue? Or should this PR not fully close it?

[DrewKimball]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @rytaft and @yuzefovich)

---

pkg/internal/sqlsmith/plpgsql.go line 90 at r5 (raw file):

Previously, yuzefovich (Yahor Yuzefovich) wrote…

I'm a bit confused by this comment - can you expand on it? Is it effectively saying that we don't need to count the number of times Next is called when it returns ok = false because at some point NULL stmt is returned which will have ok = true, so infinite loop is impossible?

Yes, that's exactly it. I modified the comment to explain that better.

---

pkg/internal/sqlsmith/plpgsql.go line 109 at r5 (raw file):

Previously, yuzefovich (Yahor Yuzefovich) wrote…

nit: perhaps s/numElsIfs/numElseIfs/.

Done.

---

pkg/internal/sqlsmith/plpgsql.go line 136 at r5 (raw file):

Previously, yuzefovich (Yahor Yuzefovich) wrote…

nit: this issue is being closed by this PR right now - should this refer to a different issue? Or should this PR not fully close it?

Good point. I'll leave the issue open to track support for other statements.

[yuzefovich]

Reviewed 8 of 9 files at r1, 1 of 3 files at r7, 2 of 2 files at r8, 3 of 3 files at r9, 5 of 5 files at r10, 17 of 17 files at r11, 16 of 16 files at r12, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @rytaft)

---

pkg/internal/sqlsmith/plpgsql.go line 109 at r5 (raw file):

Previously, DrewKimball (Drew Kimball) wrote…

Done.

Sorry, I didn't realize that ELSIF is the keyword - up to you whether you want to revert the change in response to my comment.

[DrewKimball]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @rytaft)

---

pkg/internal/sqlsmith/plpgsql.go line 109 at r5 (raw file):

Previously, yuzefovich (Yahor Yuzefovich) wrote…

Sorry, I didn't realize that ELSIF is the keyword - up to you whether you want to revert the change in response to my comment.

Eh, I think numElseIfs is good. TFYR!

[DrewKimball]

bors r+

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)